Basic RDF-star support

No parsing and SPARQL support yet

lib/README.md

@@ -37,7 +37,7 @@ let store = Store::open("example.db")?;
 
 // insertion
 let ex = NamedNode::new("http://example.com")?;
-let quad = Quad::new(ex.clone(), ex.clone(), ex.clone(), None);
+let quad = Quad::new(ex.clone(), ex.clone(), ex.clone(), GraphName::DefaultGraph);
 store.insert(&quad)?;
 
 // quad filter

lib/benches/store.rs

@@ -1,5 +1,5 @@
 use criterion::{criterion_group, criterion_main, BenchmarkId, Criterion, Throughput};
-use oxigraph::model::{Dataset, Graph, NamedNode, Quad, Triple};
+use oxigraph::model::{Dataset, Graph, GraphName, NamedNode, Quad, Triple};
 use oxigraph::store::Store;
 use rand::random;
 use std::iter::FromIterator;
@@ -80,7 +80,7 @@ fn create_quads(size: u64) -> Vec<Quad> {
                     "http://example.com/id/{}",
                     random::<u64>() % size
                 )),
-                None,
+                GraphName::DefaultGraph,
             )
         })
         .collect()

lib/src/lib.rs

@@ -21,7 +21,7 @@
 //!
 //! // insertion
 //! let ex = NamedNode::new("http://example.com")?;
-//! let quad = Quad::new(ex.clone(), ex.clone(), ex.clone(), None);
+//! let quad = Quad::new(ex.clone(), ex.clone(), ex.clone(), GraphName::DefaultGraph);
 //! store.insert(&quad)?;
 //!
 //! // quad filter

lib/src/model/dataset.rs

@@ -29,7 +29,6 @@ use crate::io::{
 use crate::model::interning::*;
 use crate::model::SubjectRef;
 use crate::model::*;
-use lasso::Rodeo;
 use std::collections::hash_map::DefaultHasher;
 use std::collections::BTreeSet;
 use std::collections::{HashMap, HashSet};
@@ -66,7 +65,8 @@ use std::{fmt, io};
 /// ```
 #[derive(Debug, Default)]
 pub struct Dataset {
-    interner: Rodeo,
+    interner: Interner,
+    triples: HashMap<InternedTriple, Triple>,
     gspo: BTreeSet<(
         InternedGraphName,
         InternedSubject,
@@ -607,9 +607,13 @@ impl Dataset {
         for (g, s, _, o) in &self.gspo {
             if let InternedSubject::BlankNode(bnode) = s {
                 bnodes.insert(*bnode);
+            } else if let InternedSubject::Triple(triple) = s {
+                self.triple_blank_nodes(triple, &mut bnodes);
             }
             if let InternedTerm::BlankNode(bnode) = o {
                 bnodes.insert(*bnode);
+            } else if let InternedTerm::Triple(triple) = o {
+                self.triple_blank_nodes(triple, &mut bnodes);
             }
             if let InternedGraphName::BlankNode(bnode) = g {
                 bnodes.insert(*bnode);
@@ -618,6 +622,19 @@ impl Dataset {
         bnodes
     }
 
+    fn triple_blank_nodes(&self, triple: &InternedTriple, bnodes: &mut HashSet<InternedBlankNode>) {
+        if let InternedSubject::BlankNode(bnode) = &triple.subject {
+            bnodes.insert(*bnode);
+        } else if let InternedSubject::Triple(t) = &triple.subject {
+            self.triple_blank_nodes(t, bnodes);
+        }
+        if let InternedTerm::BlankNode(bnode) = &triple.object {
+            bnodes.insert(*bnode);
+        } else if let InternedTerm::Triple(t) = &triple.object {
+            self.triple_blank_nodes(t, bnodes);
+        }
+    }
+
     fn hash_bnodes(
         &self,
         mut hashes: HashMap<InternedBlankNode, u64>,
@@ -688,7 +705,9 @@ impl Dataset {
         bnodes_hash: &HashMap<InternedBlankNode, u64>,
     ) -> u64 {
         if let InternedSubject::BlankNode(bnode) = node {
-            *bnodes_hash.get(bnode).unwrap()
+            bnodes_hash[bnode]
+        } else if let InternedSubject::Triple(triple) = node {
+            self.hash_triple(triple, bnodes_hash)
         } else {
             self.hash_tuple(node.decode_from(&self.interner))
         }
@@ -696,7 +715,9 @@ impl Dataset {
 
     fn hash_term(&self, term: &InternedTerm, bnodes_hash: &HashMap<InternedBlankNode, u64>) -> u64 {
         if let InternedTerm::BlankNode(bnode) = term {
-            *bnodes_hash.get(bnode).unwrap()
+            bnodes_hash[bnode]
+        } else if let InternedTerm::Triple(triple) = term {
+            self.hash_triple(triple, bnodes_hash)
         } else {
             self.hash_tuple(term.decode_from(&self.interner))
         }
@@ -708,12 +729,24 @@ impl Dataset {
         bnodes_hash: &HashMap<InternedBlankNode, u64>,
     ) -> u64 {
         if let InternedGraphName::BlankNode(bnode) = graph_name {
-            *bnodes_hash.get(bnode).unwrap()
+            bnodes_hash[bnode]
         } else {
             self.hash_tuple(graph_name.decode_from(&self.interner))
         }
     }
 
+    fn hash_triple(
+        &self,
+        triple: &InternedTriple,
+        bnodes_hash: &HashMap<InternedBlankNode, u64>,
+    ) -> u64 {
+        self.hash_tuple((
+            self.hash_subject(&triple.subject, bnodes_hash),
+            self.hash_named_node(&triple.predicate),
+            self.hash_term(&triple.object, bnodes_hash),
+        ))
+    }
+
     fn hash_tuple(&self, v: impl Hash) -> u64 {
         let mut hasher = DefaultHasher::new();
         v.hash(&mut hasher);
@@ -775,12 +808,22 @@ impl Dataset {
                 (
                     if let InternedSubject::BlankNode(bnode) = s {
                         InternedSubject::BlankNode(self.map_bnode(&bnode, hashes))
+                    } else if let InternedSubject::Triple(triple) = s {
+                        InternedSubject::Triple(Box::new(InternedTriple::encoded_into(
+                            self.label_triple(&triple, hashes).as_ref(),
+                            &mut self.interner,
+                        )))
                     } else {
                         s
                     },
                     p,
                     if let InternedTerm::BlankNode(bnode) = o {
                         InternedTerm::BlankNode(self.map_bnode(&bnode, hashes))
+                    } else if let InternedTerm::Triple(triple) = o {
+                        InternedTerm::Triple(Box::new(InternedTriple::encoded_into(
+                            self.label_triple(&triple, hashes).as_ref(),
+                            &mut self.interner,
+                        )))
                     } else {
                         o
                     },
@@ -796,16 +839,48 @@ impl Dataset {
         quads
     }
 
+    fn label_triple(
+        &mut self,
+        triple: &InternedTriple,
+        hashes: &HashMap<InternedBlankNode, u64>,
+    ) -> Triple {
+        Triple {
+            subject: if let InternedSubject::BlankNode(bnode) = &triple.subject {
+                self.gen_bnode(bnode, hashes).into()
+            } else if let InternedSubject::Triple(t) = &triple.subject {
+                self.label_triple(t, hashes).into()
+            } else {
+                triple.subject.decode_from(&self.interner).into_owned()
+            },
+            predicate: triple.predicate.decode_from(&self.interner).into_owned(),
+            object: if let InternedTerm::BlankNode(bnode) = &triple.object {
+                self.gen_bnode(bnode, hashes).into()
+            } else if let InternedTerm::Triple(t) = &triple.object {
+                self.label_triple(t, hashes).into()
+            } else {
+                triple.object.decode_from(&self.interner).into_owned()
+            },
+        }
+    }
+
     fn map_bnode(
         &mut self,
         old_bnode: &InternedBlankNode,
         hashes: &HashMap<InternedBlankNode, u64>,
     ) -> InternedBlankNode {
         InternedBlankNode::encoded_into(
-            BlankNode::new_from_unique_id(*hashes.get(old_bnode).unwrap()).as_ref(),
+            self.gen_bnode(old_bnode, hashes).as_ref(),
             &mut self.interner,
         )
     }
+
+    fn gen_bnode(
+        &self,
+        old_bnode: &InternedBlankNode,
+        hashes: &HashMap<InternedBlankNode, u64>,
+    ) -> BlankNode {
+        BlankNode::new_from_unique_id(hashes[old_bnode])
+    }
 }
 
 impl PartialEq for Dataset {
@@ -1151,10 +1226,13 @@ impl<'a> GraphView<'a> {
 
     /// Checks if the graph contains the given triple
     pub fn contains<'b>(&self, triple: impl Into<TripleRef<'b>>) -> bool {
-        if let Some((s, p, o)) = self.encoded_triple(triple.into()) {
+        if let Some(triple) = self.encoded_triple(triple.into()) {
-            self.dataset
+            self.dataset.gspo.contains(&(
-                .gspo
+                self.graph_name.clone(),
-                .contains(&(self.graph_name.clone(), s, p, o))
+                triple.subject,
+                triple.predicate,
+                triple.object,
+            ))
         } else {
             false
         }
@@ -1195,15 +1273,12 @@ impl<'a> GraphView<'a> {
         writer.finish()
     }
 
-    fn encoded_triple(
+    fn encoded_triple(&self, triple: TripleRef<'_>) -> Option<InternedTriple> {
-        &self,
+        Some(InternedTriple {
-        triple: TripleRef<'_>,
+            subject: self.dataset.encoded_subject(triple.subject)?,
-    ) -> Option<(InternedSubject, InternedNamedNode, InternedTerm)> {
+            predicate: self.dataset.encoded_named_node(triple.predicate)?,
-        Some((
+            object: self.dataset.encoded_term(triple.object)?,
-            self.dataset.encoded_subject(triple.subject)?,
+        })
-            self.dataset.encoded_named_node(triple.predicate)?,
-            self.dataset.encoded_term(triple.object)?,
-        ))
     }
 }
 
@@ -1274,16 +1349,24 @@ impl<'a> GraphViewMut<'a> {
 
     /// Adds a triple to the graph
     pub fn insert<'b>(&mut self, triple: impl Into<TripleRef<'b>>) -> bool {
-        let (s, p, o) = self.encode_triple(triple.into());
+        let triple = self.encode_triple(triple.into());
-        self.dataset
+        self.dataset.insert_encoded((
-            .insert_encoded((s, p, o, self.graph_name.clone()))
+            triple.subject,
+            triple.predicate,
+            triple.object,
+            self.graph_name.clone(),
+        ))
     }
 
     /// Removes a concrete triple from the graph
     pub fn remove<'b>(&mut self, triple: impl Into<TripleRef<'b>>) -> bool {
-        if let Some((s, p, o)) = self.read().encoded_triple(triple.into()) {
+        if let Some(triple) = self.read().encoded_triple(triple.into()) {
-            self.dataset
+            self.dataset.remove_encoded((
-                .remove_encoded((s, p, o, self.graph_name.clone()))
+                triple.subject,
+                triple.predicate,
+                triple.object,
+                self.graph_name.clone(),
+            ))
         } else {
             false
         }
@@ -1332,15 +1415,15 @@ impl<'a> GraphViewMut<'a> {
         Ok(())
     }
 
-    fn encode_triple(
+    fn encode_triple(&mut self, triple: TripleRef<'_>) -> InternedTriple {
-        &mut self,
+        InternedTriple {
-        triple: TripleRef<'_>,
+            subject: InternedSubject::encoded_into(triple.subject, &mut self.dataset.interner),
-    ) -> (InternedSubject, InternedNamedNode, InternedTerm) {
+            predicate: InternedNamedNode::encoded_into(
-        (
+                triple.predicate,
-            InternedSubject::encoded_into(triple.subject, &mut self.dataset.interner),
+                &mut self.dataset.interner,
-            InternedNamedNode::encoded_into(triple.predicate, &mut self.dataset.interner),
+            ),
-            InternedTerm::encoded_into(triple.object, &mut self.dataset.interner),
+            object: InternedTerm::encoded_into(triple.object, &mut self.dataset.interner),
-        )
+        }
     }
 
     /// Returns all the triples contained by the graph

lib/src/model/interning.rs

@@ -2,28 +2,35 @@
 
 use crate::model::*;
 use lasso::{Key, Rodeo, Spur};
+use std::collections::HashMap;
 use std::convert::TryInto;
 
+#[derive(Debug, Default)]
+pub struct Interner {
+    strings: Rodeo,
+    triples: HashMap<InternedTriple, Triple>,
+}
+
 #[derive(Eq, PartialEq, Ord, PartialOrd, Debug, Clone, Copy, Hash)]
 pub struct InternedNamedNode {
     id: Spur,
 }
 
 impl InternedNamedNode {
-    pub fn encoded_into(named_node: NamedNodeRef<'_>, interner: &mut Rodeo) -> Self {
+    pub fn encoded_into(named_node: NamedNodeRef<'_>, interner: &mut Interner) -> Self {
         Self {
-            id: interner.get_or_intern(named_node.as_str()),
+            id: interner.strings.get_or_intern(named_node.as_str()),
         }
     }
 
-    pub fn encoded_from(named_node: NamedNodeRef<'_>, interner: &Rodeo) -> Option<Self> {
+    pub fn encoded_from(named_node: NamedNodeRef<'_>, interner: &Interner) -> Option<Self> {
         Some(Self {
-            id: interner.get(named_node.as_str())?,
+            id: interner.strings.get(named_node.as_str())?,
         })
     }
 
-    pub fn decode_from<'a>(&self, interner: &'a Rodeo) -> NamedNodeRef<'a> {
+    pub fn decode_from<'a>(&self, interner: &'a Interner) -> NamedNodeRef<'a> {
-        NamedNodeRef::new_unchecked(interner.resolve(&self.id))
+        NamedNodeRef::new_unchecked(interner.strings.resolve(&self.id))
     }
 
     pub fn first() -> Self {
@@ -49,20 +56,20 @@ pub struct InternedBlankNode {
 }
 
 impl InternedBlankNode {
-    pub fn encoded_into(blank_node: BlankNodeRef<'_>, interner: &mut Rodeo) -> Self {
+    pub fn encoded_into(blank_node: BlankNodeRef<'_>, interner: &mut Interner) -> Self {
         Self {
-            id: interner.get_or_intern(blank_node.as_str()),
+            id: interner.strings.get_or_intern(blank_node.as_str()),
         }
     }
 
-    pub fn encoded_from(blank_node: BlankNodeRef<'_>, interner: &Rodeo) -> Option<Self> {
+    pub fn encoded_from(blank_node: BlankNodeRef<'_>, interner: &Interner) -> Option<Self> {
         Some(Self {
-            id: interner.get(blank_node.as_str())?,
+            id: interner.strings.get(blank_node.as_str())?,
         })
     }
 
-    pub fn decode_from<'a>(&self, interner: &'a Rodeo) -> BlankNodeRef<'a> {
+    pub fn decode_from<'a>(&self, interner: &'a Interner) -> BlankNodeRef<'a> {
-        BlankNodeRef::new_unchecked(interner.resolve(&self.id))
+        BlankNodeRef::new_unchecked(interner.strings.resolve(&self.id))
     }
 
     pub fn next(&self) -> Self {
@@ -88,13 +95,13 @@ pub enum InternedLiteral {
 }
 
 impl InternedLiteral {
-    pub fn encoded_into(literal: LiteralRef<'_>, interner: &mut Rodeo) -> Self {
+    pub fn encoded_into(literal: LiteralRef<'_>, interner: &mut Interner) -> Self {
-        let value_id = interner.get_or_intern(literal.value());
+        let value_id = interner.strings.get_or_intern(literal.value());
         if literal.is_plain() {
             if let Some(language) = literal.language() {
                 Self::LanguageTaggedString {
                     value_id,
-                    language_id: interner.get_or_intern(language),
+                    language_id: interner.strings.get_or_intern(language),
                 }
             } else {
                 Self::String { value_id }
@@ -107,13 +114,13 @@ impl InternedLiteral {
         }
     }
 
-    pub fn encoded_from(literal: LiteralRef<'_>, interner: &Rodeo) -> Option<Self> {
+    pub fn encoded_from(literal: LiteralRef<'_>, interner: &Interner) -> Option<Self> {
-        let value_id = interner.get(literal.value())?;
+        let value_id = interner.strings.get(literal.value())?;
         Some(if literal.is_plain() {
             if let Some(language) = literal.language() {
                 Self::LanguageTaggedString {
                     value_id,
-                    language_id: interner.get(language)?,
+                    language_id: interner.strings.get(language)?,
                 }
             } else {
                 Self::String { value_id }
@@ -126,20 +133,20 @@ impl InternedLiteral {
         })
     }
 
-    pub fn decode_from<'a>(&self, interner: &'a Rodeo) -> LiteralRef<'a> {
+    pub fn decode_from<'a>(&self, interner: &'a Interner) -> LiteralRef<'a> {
         match self {
             InternedLiteral::String { value_id } => {
-                LiteralRef::new_simple_literal(interner.resolve(value_id))
+                LiteralRef::new_simple_literal(interner.strings.resolve(value_id))
             }
             InternedLiteral::LanguageTaggedString {
                 value_id,
                 language_id,
             } => LiteralRef::new_language_tagged_literal_unchecked(
-                interner.resolve(value_id),
+                interner.strings.resolve(value_id),
-                interner.resolve(language_id),
+                interner.strings.resolve(language_id),
             ),
             InternedLiteral::TypedLiteral { value_id, datatype } => LiteralRef::new_typed_literal(
-                interner.resolve(value_id),
+                interner.strings.resolve(value_id),
                 datatype.decode_from(interner),
             ),
         }
@@ -169,10 +176,11 @@ impl InternedLiteral {
 pub enum InternedSubject {
     NamedNode(InternedNamedNode),
     BlankNode(InternedBlankNode),
+    Triple(Box<InternedTriple>),
 }
 
 impl InternedSubject {
-    pub fn encoded_into(node: SubjectRef<'_>, interner: &mut Rodeo) -> Self {
+    pub fn encoded_into(node: SubjectRef<'_>, interner: &mut Interner) -> Self {
         match node {
             SubjectRef::NamedNode(node) => {
                 Self::NamedNode(InternedNamedNode::encoded_into(node, interner))
@@ -180,10 +188,14 @@ impl InternedSubject {
             SubjectRef::BlankNode(node) => {
                 Self::BlankNode(InternedBlankNode::encoded_into(node, interner))
             }
+            SubjectRef::Triple(triple) => Self::Triple(Box::new(InternedTriple::encoded_into(
+                triple.as_ref(),
+                interner,
+            ))),
         }
     }
 
-    pub fn encoded_from(node: SubjectRef<'_>, interner: &Rodeo) -> Option<Self> {
+    pub fn encoded_from(node: SubjectRef<'_>, interner: &Interner) -> Option<Self> {
         Some(match node {
             SubjectRef::NamedNode(node) => {
                 Self::NamedNode(InternedNamedNode::encoded_from(node, interner)?)
@@ -191,13 +203,18 @@ impl InternedSubject {
             SubjectRef::BlankNode(node) => {
                 Self::BlankNode(InternedBlankNode::encoded_from(node, interner)?)
             }
+            SubjectRef::Triple(triple) => Self::Triple(Box::new(InternedTriple::encoded_from(
+                triple.as_ref(),
+                interner,
+            )?)),
         })
     }
 
-    pub fn decode_from<'a>(&self, interner: &'a Rodeo) -> SubjectRef<'a> {
+    pub fn decode_from<'a>(&self, interner: &'a Interner) -> SubjectRef<'a> {
         match self {
             Self::NamedNode(node) => SubjectRef::NamedNode(node.decode_from(interner)),
             Self::BlankNode(node) => SubjectRef::BlankNode(node.decode_from(interner)),
+            Self::Triple(triple) => SubjectRef::Triple(&interner.triples[triple.as_ref()]),
         }
     }
 
@@ -209,6 +226,7 @@ impl InternedSubject {
         match self {
             Self::NamedNode(node) => Self::NamedNode(node.next()),
             Self::BlankNode(node) => Self::BlankNode(node.next()),
+            Self::Triple(triple) => Self::Triple(Box::new(triple.next())),
         }
     }
 
@@ -225,7 +243,7 @@ pub enum InternedGraphName {
 }
 
 impl InternedGraphName {
-    pub fn encoded_into(node: GraphNameRef<'_>, interner: &mut Rodeo) -> Self {
+    pub fn encoded_into(node: GraphNameRef<'_>, interner: &mut Interner) -> Self {
         match node {
             GraphNameRef::DefaultGraph => Self::DefaultGraph,
             GraphNameRef::NamedNode(node) => {
@@ -237,7 +255,7 @@ impl InternedGraphName {
         }
     }
 
-    pub fn encoded_from(node: GraphNameRef<'_>, interner: &Rodeo) -> Option<Self> {
+    pub fn encoded_from(node: GraphNameRef<'_>, interner: &Interner) -> Option<Self> {
         Some(match node {
             GraphNameRef::DefaultGraph => Self::DefaultGraph,
             GraphNameRef::NamedNode(node) => {
@@ -249,7 +267,7 @@ impl InternedGraphName {
         })
     }
 
-    pub fn decode_from<'a>(&self, interner: &'a Rodeo) -> GraphNameRef<'a> {
+    pub fn decode_from<'a>(&self, interner: &'a Interner) -> GraphNameRef<'a> {
         match self {
             Self::DefaultGraph => GraphNameRef::DefaultGraph,
             Self::NamedNode(node) => GraphNameRef::NamedNode(node.decode_from(interner)),
@@ -279,10 +297,11 @@ pub enum InternedTerm {
     NamedNode(InternedNamedNode),
     BlankNode(InternedBlankNode),
     Literal(InternedLiteral),
+    Triple(Box<InternedTriple>),
 }
 
 impl InternedTerm {
-    pub fn encoded_into(term: TermRef<'_>, interner: &mut Rodeo) -> Self {
+    pub fn encoded_into(term: TermRef<'_>, interner: &mut Interner) -> Self {
         match term {
             TermRef::NamedNode(term) => {
                 Self::NamedNode(InternedNamedNode::encoded_into(term, interner))
@@ -291,10 +310,14 @@ impl InternedTerm {
                 Self::BlankNode(InternedBlankNode::encoded_into(term, interner))
             }
             TermRef::Literal(term) => Self::Literal(InternedLiteral::encoded_into(term, interner)),
+            TermRef::Triple(triple) => Self::Triple(Box::new(InternedTriple::encoded_into(
+                triple.as_ref(),
+                interner,
+            ))),
         }
     }
 
-    pub fn encoded_from(term: TermRef<'_>, interner: &Rodeo) -> Option<Self> {
+    pub fn encoded_from(term: TermRef<'_>, interner: &Interner) -> Option<Self> {
         Some(match term {
             TermRef::NamedNode(term) => {
                 Self::NamedNode(InternedNamedNode::encoded_from(term, interner)?)
@@ -303,14 +326,19 @@ impl InternedTerm {
                 Self::BlankNode(InternedBlankNode::encoded_from(term, interner)?)
             }
             TermRef::Literal(term) => Self::Literal(InternedLiteral::encoded_from(term, interner)?),
+            TermRef::Triple(triple) => Self::Triple(Box::new(InternedTriple::encoded_from(
+                triple.as_ref(),
+                interner,
+            )?)),
         })
     }
 
-    pub fn decode_from<'a>(&self, interner: &'a Rodeo) -> TermRef<'a> {
+    pub fn decode_from<'a>(&self, interner: &'a Interner) -> TermRef<'a> {
         match self {
             Self::NamedNode(term) => TermRef::NamedNode(term.decode_from(interner)),
             Self::BlankNode(term) => TermRef::BlankNode(term.decode_from(interner)),
             Self::Literal(term) => TermRef::Literal(term.decode_from(interner)),
+            Self::Triple(triple) => TermRef::Triple(&interner.triples[triple.as_ref()]),
         }
     }
 
@@ -323,6 +351,7 @@ impl InternedTerm {
             Self::NamedNode(node) => Self::NamedNode(node.next()),
             Self::BlankNode(node) => Self::BlankNode(node.next()),
             Self::Literal(node) => Self::Literal(node.next()),
+            Self::Triple(triple) => Self::Triple(Box::new(triple.next())),
         }
     }
 
@@ -331,6 +360,48 @@ impl InternedTerm {
     }
 }
 
+#[derive(Eq, PartialEq, Ord, PartialOrd, Debug, Clone, Hash)]
+pub struct InternedTriple {
+    pub subject: InternedSubject,
+    pub predicate: InternedNamedNode,
+    pub object: InternedTerm,
+}
+
+impl InternedTriple {
+    pub fn encoded_into(triple: TripleRef<'_>, interner: &mut Interner) -> Self {
+        let interned_triple = Self {
+            subject: InternedSubject::encoded_into(triple.subject, interner),
+            predicate: InternedNamedNode::encoded_into(triple.predicate, interner),
+            object: InternedTerm::encoded_into(triple.object, interner),
+        };
+        interner
+            .triples
+            .insert(interned_triple.clone(), triple.into_owned());
+        interned_triple
+    }
+
+    pub fn encoded_from(triple: TripleRef<'_>, interner: &Interner) -> Option<Self> {
+        let interned_triple = Self {
+            subject: InternedSubject::encoded_from(triple.subject, interner)?,
+            predicate: InternedNamedNode::encoded_from(triple.predicate, interner)?,
+            object: InternedTerm::encoded_from(triple.object, interner)?,
+        };
+        if interner.triples.contains_key(&interned_triple) {
+            Some(interned_triple)
+        } else {
+            None
+        }
+    }
+
+    pub fn next(&self) -> Self {
+        Self {
+            subject: self.subject.clone(),
+            predicate: self.predicate,
+            object: self.object.next(),
+        }
+    }
+}
+
 fn fist_spur() -> Spur {
     Spur::try_from_usize(0).unwrap()
 }

lib/src/model/sophia.rs

@@ -191,26 +191,26 @@ impl<'a> From<GraphNameRef<'a>> for Option<TermRef<'a>> {
 
 impl TTerm for Subject {
     fn kind(&self) -> TermKind {
-        use Subject::*;
         match self {
-            NamedNode(_) => TermKind::Iri,
+            Self::NamedNode(_) => TermKind::Iri,
-            BlankNode(_) => TermKind::BlankNode,
+            Self::BlankNode(_) => TermKind::BlankNode,
+            Self::Triple(_) => panic!("RDF-star is not supported yet by Sophia"),
         }
     }
 
     fn value_raw(&self) -> RawValue<'_> {
-        use Subject::*;
         match self {
-            NamedNode(n) => n.value_raw(),
+            Self::NamedNode(n) => n.value_raw(),
-            BlankNode(n) => n.value_raw(),
+            Self::BlankNode(n) => n.value_raw(),
+            Self::Triple(_) => panic!("RDF-star is not supported yet by Sophia"),
         }
     }
 
     fn as_dyn(&self) -> &dyn TTerm {
-        use Subject::*;
         match self {
-            NamedNode(n) => n.as_dyn(),
+            Self::NamedNode(n) => n.as_dyn(),
-            BlankNode(n) => n.as_dyn(),
+            Self::BlankNode(n) => n.as_dyn(),
+            Self::Triple(_) => panic!("RDF-star is not supported yet by Sophia"),
         }
     }
 }
@@ -232,71 +232,71 @@ impl TryCopyTerm for Subject {
 
 impl<'a> TTerm for SubjectRef<'a> {
     fn kind(&self) -> TermKind {
-        use SubjectRef::*;
         match self {
-            NamedNode(_) => TermKind::Iri,
+            Self::NamedNode(_) => TermKind::Iri,
-            BlankNode(_) => TermKind::BlankNode,
+            Self::BlankNode(_) => TermKind::BlankNode,
+            Self::Triple(_) => panic!("RDF-star is not supported yet by Sophia"),
         }
     }
 
     fn value_raw(&self) -> RawValue<'_> {
-        use SubjectRef::*;
         match self {
-            NamedNode(n) => n.value_raw(),
+            Self::NamedNode(n) => n.value_raw(),
-            BlankNode(n) => n.value_raw(),
+            Self::BlankNode(n) => n.value_raw(),
+            Self::Triple(_) => panic!("RDF-star is not supported yet by Sophia"),
         }
     }
 
     fn as_dyn(&self) -> &dyn TTerm {
-        use SubjectRef::*;
         match self {
-            NamedNode(n) => n.as_dyn(),
+            Self::NamedNode(n) => n.as_dyn(),
-            BlankNode(n) => n.as_dyn(),
+            Self::BlankNode(n) => n.as_dyn(),
+            Self::Triple(_) => panic!("RDF-star is not supported yet by Sophia"),
         }
     }
 }
 
 impl TTerm for Term {
     fn kind(&self) -> TermKind {
-        use Term::*;
         match self {
-            NamedNode(_) => TermKind::Iri,
+            Self::NamedNode(_) => TermKind::Iri,
-            BlankNode(_) => TermKind::BlankNode,
+            Self::BlankNode(_) => TermKind::BlankNode,
-            Literal(_) => TermKind::Literal,
+            Self::Literal(_) => TermKind::Literal,
+            Self::Triple(_) => panic!("RDF-star is not supported yet by Sophia"),
         }
     }
 
     fn value_raw(&self) -> RawValue<'_> {
-        use Term::*;
         match self {
-            NamedNode(n) => n.value_raw(),
+            Self::NamedNode(n) => n.value_raw(),
-            BlankNode(n) => n.value_raw(),
+            Self::BlankNode(n) => n.value_raw(),
-            Literal(l) => l.value_raw(),
+            Self::Literal(l) => l.value_raw(),
+            Self::Triple(_) => panic!("RDF-star is not supported yet by Sophia"),
         }
     }
 
     fn datatype(&self) -> Option<SimpleIri<'_>> {
-        use Term::*;
+        if let Self::Literal(l) = self {
-        match self {
+            TTerm::datatype(l)
-            Literal(l) => TTerm::datatype(l),
+        } else {
-            _ => None,
+            None
         }
     }
 
     fn language(&self) -> Option<&str> {
-        use Term::*;
+        if let Self::Literal(l) = self {
-        match self {
+            TTerm::language(l)
-            Literal(l) => TTerm::language(l),
+        } else {
-            _ => None,
+            None
         }
     }
 
     fn as_dyn(&self) -> &dyn TTerm {
-        use Term::*;
         match self {
-            NamedNode(n) => n.as_dyn(),
+            Self::NamedNode(n) => n.as_dyn(),
-            BlankNode(n) => n.as_dyn(),
+            Self::BlankNode(n) => n.as_dyn(),
-            Literal(l) => l.as_dyn(),
+            Self::Literal(l) => l.as_dyn(),
+            Self::Triple(_) => panic!("RDF-star is not supported yet by Sophia"),
         }
     }
 }
@@ -319,45 +319,45 @@ impl TryCopyTerm for Term {
 
 impl<'a> TTerm for TermRef<'a> {
     fn kind(&self) -> TermKind {
-        use TermRef::*;
         match self {
-            NamedNode(_) => TermKind::Iri,
+            Self::NamedNode(_) => TermKind::Iri,
-            BlankNode(_) => TermKind::BlankNode,
+            Self::BlankNode(_) => TermKind::BlankNode,
-            Literal(_) => TermKind::Literal,
+            Self::Literal(_) => TermKind::Literal,
+            Self::Triple(_) => panic!("RDF-star is not supported yet by Sophia"),
         }
     }
 
     fn value_raw(&self) -> RawValue<'_> {
-        use TermRef::*;
         match self {
-            NamedNode(n) => n.value_raw(),
+            Self::NamedNode(n) => n.value_raw(),
-            BlankNode(n) => n.value_raw(),
+            Self::BlankNode(n) => n.value_raw(),
-            Literal(l) => l.value_raw(),
+            Self::Literal(l) => l.value_raw(),
+            Self::Triple(_) => panic!("RDF-star is not supported yet by Sophia"),
         }
     }
 
     fn datatype(&self) -> Option<SimpleIri<'_>> {
-        use TermRef::*;
+        if let Self::Literal(l) = self {
-        match self {
+            TTerm::datatype(l)
-            Literal(l) => TTerm::datatype(l),
+        } else {
-            _ => None,
+            None
         }
     }
 
     fn language(&self) -> Option<&str> {
-        use TermRef::*;
+        if let Self::Literal(l) = self {
-        match self {
+            TTerm::language(l)
-            Literal(l) => TTerm::language(l),
+        } else {
-            _ => None,
+            None
         }
     }
 
     fn as_dyn(&self) -> &dyn TTerm {
-        use TermRef::*;
         match self {
-            NamedNode(n) => n.as_dyn(),
+            Self::NamedNode(n) => n.as_dyn(),
-            BlankNode(n) => n.as_dyn(),
+            Self::BlankNode(n) => n.as_dyn(),
-            Literal(l) => l.as_dyn(),
+            Self::Literal(l) => l.as_dyn(),
+            Self::Triple(_) => panic!("RDF-star is not supported yet by Sophia"),
         }
     }
 }

lib/src/model/triple.rs

@@ -4,12 +4,14 @@ use crate::model::named_node::NamedNode;
 use crate::model::{BlankNodeRef, LiteralRef, NamedNodeRef};
 use rio_api::model as rio;
 use std::fmt;
+use std::sync::Arc;
 
-/// The owned union of [IRIs](https://www.w3.org/TR/rdf11-concepts/#dfn-iri) and [blank nodes](https://www.w3.org/TR/rdf11-concepts/#dfn-blank-node).
+/// The owned union of [IRIs](https://www.w3.org/TR/rdf11-concepts/#dfn-iri), [blank nodes](https://www.w3.org/TR/rdf11-concepts/#dfn-blank-node)  and [triples](https://www.w3.org/TR/rdf11-concepts/#dfn-rdf-triple).
 #[derive(Eq, PartialEq, Debug, Clone, Hash)]
 pub enum Subject {
     NamedNode(NamedNode),
     BlankNode(BlankNode),
+    Triple(Arc<Triple>),
 }
 
 impl Subject {
@@ -23,11 +25,17 @@ impl Subject {
         self.as_ref().is_blank_node()
     }
 
+    #[inline]
+    pub fn is_triple(&self) -> bool {
+        self.as_ref().is_triple()
+    }
+
     #[inline]
     pub fn as_ref(&self) -> SubjectRef<'_> {
         match self {
             Self::NamedNode(node) => SubjectRef::NamedNode(node.as_ref()),
             Self::BlankNode(node) => SubjectRef::BlankNode(node.as_ref()),
+            Self::Triple(triple) => SubjectRef::Triple(triple),
         }
     }
 }
@@ -67,28 +75,42 @@ impl From<BlankNodeRef<'_>> for Subject {
     }
 }
 
-/// The borrowed union of [IRIs](https://www.w3.org/TR/rdf11-concepts/#dfn-iri) and [blank nodes](https://www.w3.org/TR/rdf11-concepts/#dfn-blank-node).
+impl From<Triple> for Subject {
+    #[inline]
+    fn from(node: Triple) -> Self {
+        Self::Triple(Arc::new(node))
+    }
+}
+
+impl From<TripleRef<'_>> for Subject {
+    #[inline]
+    fn from(node: TripleRef<'_>) -> Self {
+        node.into_owned().into()
+    }
+}
+
+/// The borrowed union of [IRIs](https://www.w3.org/TR/rdf11-concepts/#dfn-iri), [blank nodes](https://www.w3.org/TR/rdf11-concepts/#dfn-blank-node) and [triples](https://www.w3.org/TR/rdf11-concepts/#dfn-rdf-triple).
 #[derive(Eq, PartialEq, Debug, Clone, Copy, Hash)]
 pub enum SubjectRef<'a> {
     NamedNode(NamedNodeRef<'a>),
     BlankNode(BlankNodeRef<'a>),
+    Triple(&'a Triple),
 }
 
 impl<'a> SubjectRef<'a> {
     #[inline]
     pub fn is_named_node(&self) -> bool {
-        match self {
+        matches!(self, Self::NamedNode(_))
-            Self::NamedNode(_) => true,
-            Self::BlankNode(_) => false,
-        }
     }
 
     #[inline]
     pub fn is_blank_node(&self) -> bool {
-        match self {
+        matches!(self, Self::BlankNode(_))
-            Self::NamedNode(_) => false,
-            Self::BlankNode(_) => true,
     }
+
+    #[inline]
+    pub fn is_triple(&self) -> bool {
+        matches!(self, Self::Triple(_))
     }
 
     #[inline]
@@ -96,6 +118,7 @@ impl<'a> SubjectRef<'a> {
         match self {
             Self::NamedNode(node) => Subject::NamedNode(node.into_owned()),
             Self::BlankNode(node) => Subject::BlankNode(node.into_owned()),
+            Self::Triple(triple) => Subject::Triple(Arc::new(triple.clone())),
         }
     }
 }
@@ -106,6 +129,11 @@ impl fmt::Display for SubjectRef<'_> {
         match self {
             Self::NamedNode(node) => node.fmt(f),
             Self::BlankNode(node) => node.fmt(f),
+            Self::Triple(triple) => write!(
+                f,
+                "<< {} {} {} >>",
+                triple.subject, triple.predicate, triple.object
+            ),
         }
     }
 }
@@ -138,6 +166,13 @@ impl<'a> From<&'a BlankNode> for SubjectRef<'a> {
     }
 }
 
+impl<'a> From<&'a Triple> for SubjectRef<'a> {
+    #[inline]
+    fn from(node: &'a Triple) -> Self {
+        Self::Triple(node)
+    }
+}
+
 impl<'a> From<&'a Subject> for SubjectRef<'a> {
     #[inline]
     fn from(node: &'a Subject) -> Self {
@@ -152,23 +187,26 @@ impl<'a> From<SubjectRef<'a>> for Subject {
     }
 }
 
+#[allow(clippy::unimplemented, clippy::fallible_impl_from)]
 impl<'a> From<SubjectRef<'a>> for rio::NamedOrBlankNode<'a> {
     #[inline]
     fn from(node: SubjectRef<'a>) -> Self {
         match node {
             SubjectRef::NamedNode(node) => rio::NamedNode::from(node).into(),
             SubjectRef::BlankNode(node) => rio::BlankNode::from(node).into(),
+            SubjectRef::Triple(_) => unimplemented!("Rio library does not support RDF* yet"),
         }
     }
 }
 
 /// An owned RDF [term](https://www.w3.org/TR/rdf11-concepts/#dfn-rdf-term)
-/// It is the union of [IRIs](https://www.w3.org/TR/rdf11-concepts/#dfn-iri), [blank nodes](https://www.w3.org/TR/rdf11-concepts/#dfn-blank-node) and [literals](https://www.w3.org/TR/rdf11-concepts/#dfn-literal).
+/// It is the union of [IRIs](https://www.w3.org/TR/rdf11-concepts/#dfn-iri), [blank nodes](https://www.w3.org/TR/rdf11-concepts/#dfn-blank-node), [literals](https://www.w3.org/TR/rdf11-concepts/#dfn-literal) and [triples](https://www.w3.org/TR/rdf11-concepts/#dfn-rdf-triple).
 #[derive(Eq, PartialEq, Debug, Clone, Hash)]
 pub enum Term {
     NamedNode(NamedNode),
     BlankNode(BlankNode),
     Literal(Literal),
+    Triple(Arc<Triple>),
 }
 
 impl Term {
@@ -187,12 +225,18 @@ impl Term {
         self.as_ref().is_literal()
     }
 
+    #[inline]
+    pub fn is_triple(&self) -> bool {
+        self.as_ref().is_triple()
+    }
+
     #[inline]
     pub fn as_ref(&self) -> TermRef<'_> {
         match self {
             Self::NamedNode(node) => TermRef::NamedNode(node.as_ref()),
             Self::BlankNode(node) => TermRef::BlankNode(node.as_ref()),
             Self::Literal(literal) => TermRef::Literal(literal.as_ref()),
+            Self::Triple(triple) => TermRef::Triple(triple),
         }
     }
 }
@@ -245,6 +289,19 @@ impl From<LiteralRef<'_>> for Term {
         literal.into_owned().into()
     }
 }
+impl From<Triple> for Term {
+    #[inline]
+    fn from(triple: Triple) -> Self {
+        Self::Triple(Arc::new(triple))
+    }
+}
+
+impl From<TripleRef<'_>> for Term {
+    #[inline]
+    fn from(triple: TripleRef<'_>) -> Self {
+        triple.into_owned().into()
+    }
+}
 
 impl From<Subject> for Term {
     #[inline]
@@ -252,6 +309,7 @@ impl From<Subject> for Term {
         match node {
             Subject::NamedNode(node) => node.into(),
             Subject::BlankNode(node) => node.into(),
+            Subject::Triple(triple) => Self::Triple(triple),
         }
     }
 }
@@ -264,12 +322,13 @@ impl From<SubjectRef<'_>> for Term {
 }
 
 /// A borrowed RDF [term](https://www.w3.org/TR/rdf11-concepts/#dfn-rdf-term)
-/// It is the union of [IRIs](https://www.w3.org/TR/rdf11-concepts/#dfn-iri), [blank nodes](https://www.w3.org/TR/rdf11-concepts/#dfn-blank-node) and [literals](https://www.w3.org/TR/rdf11-concepts/#dfn-literal).
+/// It is the union of [IRIs](https://www.w3.org/TR/rdf11-concepts/#dfn-iri), [blank nodes](https://www.w3.org/TR/rdf11-concepts/#dfn-blank-node), [literals](https://www.w3.org/TR/rdf11-concepts/#dfn-literal) and [triples](https://www.w3.org/TR/rdf11-concepts/#dfn-rdf-triple).
 #[derive(Eq, PartialEq, Debug, Clone, Copy, Hash)]
 pub enum TermRef<'a> {
     NamedNode(NamedNodeRef<'a>),
     BlankNode(BlankNodeRef<'a>),
     Literal(LiteralRef<'a>),
+    Triple(&'a Triple),
 }
 
 impl<'a> TermRef<'a> {
@@ -288,12 +347,18 @@ impl<'a> TermRef<'a> {
         matches!(self, Self::Literal(_))
     }
 
+    #[inline]
+    pub fn is_triple(&self) -> bool {
+        matches!(self, Self::Triple(_))
+    }
+
     #[inline]
     pub fn into_owned(self) -> Term {
         match self {
             Self::NamedNode(node) => Term::NamedNode(node.into_owned()),
             Self::BlankNode(node) => Term::BlankNode(node.into_owned()),
             Self::Literal(literal) => Term::Literal(literal.into_owned()),
+            Self::Triple(triple) => Term::Triple(Arc::new(triple.clone())),
         }
     }
 }
@@ -304,7 +369,14 @@ impl fmt::Display for TermRef<'_> {
         match self {
             Self::NamedNode(node) => node.fmt(f),
             Self::BlankNode(node) => node.fmt(f),
-            Self::Literal(node) => node.fmt(f),
+            Self::Literal(literal) => literal.fmt(f),
+            Self::Triple(triple) => {
+                write!(
+                    f,
+                    "<< {} {} {} >>",
+                    triple.subject, triple.predicate, triple.object
+                )
+            }
         }
     }
 }
@@ -351,12 +423,20 @@ impl<'a> From<&'a Literal> for TermRef<'a> {
     }
 }
 
+impl<'a> From<&'a Triple> for TermRef<'a> {
+    #[inline]
+    fn from(node: &'a Triple) -> Self {
+        Self::Triple(node)
+    }
+}
+
 impl<'a> From<SubjectRef<'a>> for TermRef<'a> {
     #[inline]
     fn from(node: SubjectRef<'a>) -> Self {
         match node {
             SubjectRef::NamedNode(node) => node.into(),
             SubjectRef::BlankNode(node) => node.into(),
+            SubjectRef::Triple(triple) => triple.into(),
         }
     }
 }
@@ -382,6 +462,7 @@ impl<'a> From<TermRef<'a>> for Term {
     }
 }
 
+#[allow(clippy::unimplemented, clippy::fallible_impl_from)]
 impl<'a> From<TermRef<'a>> for rio::Term<'a> {
     #[inline]
     fn from(node: TermRef<'a>) -> Self {
@@ -389,6 +470,7 @@ impl<'a> From<TermRef<'a>> for rio::Term<'a> {
             TermRef::NamedNode(node) => rio::NamedNode::from(node).into(),
             TermRef::BlankNode(node) => rio::BlankNode::from(node).into(),
             TermRef::Literal(node) => rio::Literal::from(node).into(),
+            TermRef::Triple(_) => unimplemented!("Rio library does not support RDF* yet"),
         }
     }
 }
@@ -600,45 +682,6 @@ impl From<BlankNodeRef<'_>> for GraphName {
     }
 }
 
-impl From<Subject> for GraphName {
-    #[inline]
-    fn from(node: Subject) -> Self {
-        match node {
-            Subject::NamedNode(node) => node.into(),
-            Subject::BlankNode(node) => node.into(),
-        }
-    }
-}
-
-impl From<SubjectRef<'_>> for GraphName {
-    #[inline]
-    fn from(node: SubjectRef<'_>) -> Self {
-        node.into_owned().into()
-    }
-}
-
-impl From<Option<Subject>> for GraphName {
-    #[inline]
-    fn from(name: Option<Subject>) -> Self {
-        if let Some(node) = name {
-            node.into()
-        } else {
-            GraphName::DefaultGraph
-        }
-    }
-}
-
-impl From<GraphName> for Option<Subject> {
-    #[inline]
-    fn from(name: GraphName) -> Self {
-        match name {
-            GraphName::NamedNode(node) => Some(node.into()),
-            GraphName::BlankNode(node) => Some(node.into()),
-            GraphName::DefaultGraph => None,
-        }
-    }
-}
-
 /// A possible borrowed graph name.
 /// It is the union of [IRIs](https://www.w3.org/TR/rdf11-concepts/#dfn-iri), [blank nodes](https://www.w3.org/TR/rdf11-concepts/#dfn-blank-node), and the [default graph name](https://www.w3.org/TR/rdf11-concepts/#dfn-default-graph).
 #[derive(Eq, PartialEq, Debug, Clone, Copy, Hash)]
@@ -713,23 +756,6 @@ impl<'a> From<&'a BlankNode> for GraphNameRef<'a> {
     }
 }
 
-impl<'a> From<SubjectRef<'a>> for GraphNameRef<'a> {
-    #[inline]
-    fn from(node: SubjectRef<'a>) -> Self {
-        match node {
-            SubjectRef::NamedNode(node) => node.into(),
-            SubjectRef::BlankNode(node) => node.into(),
-        }
-    }
-}
-
-impl<'a> From<&'a Subject> for GraphNameRef<'a> {
-    #[inline]
-    fn from(node: &'a Subject) -> Self {
-        node.as_ref().into()
-    }
-}
-
 impl<'a> From<&'a GraphName> for GraphNameRef<'a> {
     #[inline]
     fn from(node: &'a GraphName) -> Self {
@@ -744,28 +770,6 @@ impl<'a> From<GraphNameRef<'a>> for GraphName {
     }
 }
 
-impl<'a> From<Option<SubjectRef<'a>>> for GraphNameRef<'a> {
-    #[inline]
-    fn from(name: Option<SubjectRef<'a>>) -> Self {
-        if let Some(node) = name {
-            node.into()
-        } else {
-            GraphNameRef::DefaultGraph
-        }
-    }
-}
-
-impl<'a> From<GraphNameRef<'a>> for Option<SubjectRef<'a>> {
-    #[inline]
-    fn from(name: GraphNameRef<'a>) -> Self {
-        match name {
-            GraphNameRef::NamedNode(node) => Some(node.into()),
-            GraphNameRef::BlankNode(node) => Some(node.into()),
-            GraphNameRef::DefaultGraph => None,
-        }
-    }
-}
-
 impl<'a> From<GraphNameRef<'a>> for Option<rio::NamedOrBlankNode<'a>> {
     #[inline]
     fn from(name: GraphNameRef<'a>) -> Self {

lib/src/sparql/csv_results.rs

@@ -59,18 +59,25 @@ pub fn write_csv_results(
     Ok(())
 }
 
-fn write_csv_term<'a>(term: impl Into<TermRef<'a>>, mut sink: impl Write) -> io::Result<()> {
+fn write_csv_term<'a>(term: impl Into<TermRef<'a>>, sink: &mut impl Write) -> io::Result<()> {
     match term.into() {
         TermRef::NamedNode(uri) => sink.write_all(uri.as_str().as_bytes()),
         TermRef::BlankNode(bnode) => {
             sink.write_all(b"_:")?;
             sink.write_all(bnode.as_str().as_bytes())
         }
-        TermRef::Literal(literal) => write_escaped_csv_string(literal.value(), &mut sink),
+        TermRef::Literal(literal) => write_escaped_csv_string(literal.value(), sink),
+        TermRef::Triple(triple) => {
+            write_csv_term(&triple.subject, sink)?;
+            sink.write_all(b" ")?;
+            write_csv_term(&triple.predicate, sink)?;
+            sink.write_all(b" ")?;
+            write_csv_term(&triple.object, sink)
+        }
     }
 }
 
-fn write_escaped_csv_string(s: &str, mut sink: impl Write) -> io::Result<()> {
+fn write_escaped_csv_string(s: &str, sink: &mut impl Write) -> io::Result<()> {
     if s.bytes().any(|c| matches!(c, b'"' | b',' | b'\n' | b'\r')) {
         sink.write_all(b"\"")?;
         for c in s.bytes() {
@@ -138,7 +145,7 @@ pub fn write_tsv_results(
     Ok(())
 }
 
-fn write_tsv_term<'a>(term: impl Into<TermRef<'a>>, mut sink: impl Write) -> io::Result<()> {
+fn write_tsv_term<'a>(term: impl Into<TermRef<'a>>, sink: &mut impl Write) -> io::Result<()> {
     //TODO: full Turtle serialization
     match term.into() {
         TermRef::NamedNode(node) => write!(sink, "<{}>", node.as_str()),
@@ -158,6 +165,16 @@ fn write_tsv_term<'a>(term: impl Into<TermRef<'a>>, mut sink: impl Write) -> io:
             }
             _ => sink.write_all(literal.to_string().as_bytes()),
         },
+        TermRef::Triple(triple) => {
+            sink.write_all(b"<< ")?;
+            write_tsv_term(&triple.subject, sink)?;
+            sink.write_all(b" ")?;
+            write_tsv_term(&triple.predicate, sink)?;
+            sink.write_all(b" ")?;
+            write_tsv_term(&triple.object, sink)?;
+            sink.write_all(b" >>")?;
+            Ok(())
+        }
     }
 }
 

lib/src/sparql/eval.rs

@@ -1590,7 +1590,8 @@ impl SimpleEvaluator {
             EncodedTerm::NamedNode { iri_id } => Some((*iri_id).into()),
             EncodedTerm::NumericalBlankNode { .. }
             | EncodedTerm::SmallBlankNode { .. }
-            | EncodedTerm::BigBlankNode { .. } => None,
+            | EncodedTerm::BigBlankNode { .. }
+            | EncodedTerm::Triple(_) => None,
             EncodedTerm::SmallStringLiteral(value)
             | EncodedTerm::SmallSmallLangStringLiteral { value, .. }
             | EncodedTerm::SmallBigLangStringLiteral { value, .. }
@@ -2005,6 +2006,17 @@ impl SimpleEvaluator {
                 _ if b.is_unknown_typed_literal() => None,
                 _ => Some(false),
             },
+            EncodedTerm::Triple(a) => {
+                if let EncodedTerm::Triple(b) = b {
+                    Some(
+                        self.equals(&a.subject, &b.subject)?
+                            && self.equals(&a.predicate, &b.predicate)?
+                            && self.equals(&a.object, &b.object)?,
+                    )
+                } else {
+                    Some(false)
+                }
+            }
         }
     }
 
@@ -2194,7 +2206,8 @@ impl SimpleEvaluator {
             | EncodedTerm::SmallBlankNode { .. }
             | EncodedTerm::BigBlankNode { .. }
             | EncodedTerm::NumericalBlankNode { .. }
-            | EncodedTerm::DefaultGraph => None,
+            | EncodedTerm::DefaultGraph
+            | EncodedTerm::Triple(_) => None,
             EncodedTerm::SmallStringLiteral(_) | EncodedTerm::BigStringLiteral { .. } => {
                 self.build_named_node(xsd::STRING.as_str())
             }

lib/src/sparql/json_results.rs

@@ -47,44 +47,59 @@ pub fn write_json_results(
                         sink.write_all(b",")?;
                     }
                     write_escaped_json_string(variable.as_str(), &mut sink)?;
-                    match value {
+                    sink.write_all(b":")?;
-                        Term::NamedNode(uri) => {
+                    write_json_term(value.as_ref(), &mut sink)?;
-                            sink.write_all(b":{\"type\":\"uri\",\"value\":")?;
+                }
-                            write_escaped_json_string(uri.as_str(), &mut sink)?;
+                sink.write_all(b"}")?;
+            }
+            sink.write_all(b"]}}")?;
+            Ok(())
+        }
+        QueryResults::Graph(_) => Err(invalid_input_error(
+            "Graphs could not be formatted to SPARQL query results XML format",
+        )
+        .into()),
+    }
+}
+
+fn write_json_term(term: TermRef<'_>, sink: &mut impl Write) -> Result<(), EvaluationError> {
+    match term {
+        TermRef::NamedNode(uri) => {
+            sink.write_all(b"{\"type\":\"uri\",\"value\":")?;
+            write_escaped_json_string(uri.as_str(), sink)?;
             sink.write_all(b"}")?;
         }
-                        Term::BlankNode(bnode) => {
+        TermRef::BlankNode(bnode) => {
-                            sink.write_all(b":{\"type\":\"bnode\",\"value\":")?;
+            sink.write_all(b"{\"type\":\"bnode\",\"value\":")?;
-                            write_escaped_json_string(bnode.as_str(), &mut sink)?;
+            write_escaped_json_string(bnode.as_str(), sink)?;
             sink.write_all(b"}")?;
         }
-                        Term::Literal(literal) => {
+        TermRef::Literal(literal) => {
-                            sink.write_all(b":{\"type\":\"literal\",\"value\":")?;
+            sink.write_all(b"{\"type\":\"literal\",\"value\":")?;
-                            write_escaped_json_string(literal.value(), &mut sink)?;
+            write_escaped_json_string(literal.value(), sink)?;
             if let Some(language) = literal.language() {
                 sink.write_all(b",\"xml:lang\":")?;
-                                write_escaped_json_string(language, &mut sink)?;
+                write_escaped_json_string(language, sink)?;
             } else if !literal.is_plain() {
                 sink.write_all(b",\"datatype\":")?;
-                                write_escaped_json_string(literal.datatype().as_str(), &mut sink)?;
+                write_escaped_json_string(literal.datatype().as_str(), sink)?;
             }
             sink.write_all(b"}")?;
         }
+        TermRef::Triple(triple) => {
+            sink.write_all(b":{\"type\":\"triple\",\"value\":{\"subject\":")?;
+            write_json_term(triple.subject.as_ref().into(), sink)?;
+            sink.write_all(b":,\"predicate\":")?;
+            write_json_term(triple.predicate.as_ref().into(), sink)?;
+            sink.write_all(b":,\"object\":")?;
+            write_json_term(triple.object.as_ref(), sink)?;
+            sink.write_all(b"}}")?;
         }
     }
-                sink.write_all(b"}")?;
-            }
-            sink.write_all(b"]}}")?;
     Ok(())
 }
-        QueryResults::Graph(_) => Err(invalid_input_error(
-            "Graphs could not be formatted to SPARQL query results XML format",
-        )
-        .into()),
-    }
-}
 
-fn write_escaped_json_string(s: &str, mut sink: impl Write) -> Result<(), EvaluationError> {
+fn write_escaped_json_string(s: &str, sink: &mut impl Write) -> Result<(), EvaluationError> {
     sink.write_all(b"\"")?;
     for c in s.chars() {
         match c {

lib/src/sparql/update.rs

@@ -129,7 +129,7 @@ impl<'a> SimpleUpdateEvaluator<'a> {
                 .into_iter()
                 .map(|t| {
                     Ok(if let Some(t) = t {
-                        let r: Result<_, EvaluationError> = t.on_each_id(|id| {
+                        let r: Result<_, EvaluationError> = t.on_each_id(&mut |id| {
                             self.storage.insert_str(
                                 id,
                                 &dataset.get_str(id)?.ok_or_else(|| {

lib/src/sparql/xml_results.rs

@@ -88,8 +88,30 @@ fn write_solutions(solutions: QuerySolutionIter, sink: impl Write) -> Result<(),
             writer
                 .write_event(Event::Start(binding_tag))
                 .map_err(map_xml_error)?;
-            match value {
+            write_xml_term(value.as_ref(), &mut writer)?;
-                Term::NamedNode(uri) => {
+            writer
+                .write_event(Event::End(BytesEnd::borrowed(b"binding")))
+                .map_err(map_xml_error)?;
+        }
+        writer
+            .write_event(Event::End(BytesEnd::borrowed(b"result")))
+            .map_err(map_xml_error)?;
+    }
+    writer
+        .write_event(Event::End(BytesEnd::borrowed(b"results")))
+        .map_err(map_xml_error)?;
+    writer
+        .write_event(Event::End(BytesEnd::borrowed(b"sparql")))
+        .map_err(map_xml_error)?;
+    Ok(())
+}
+
+fn write_xml_term(
+    term: TermRef<'_>,
+    writer: &mut Writer<impl Write>,
+) -> Result<(), EvaluationError> {
+    match term {
+        TermRef::NamedNode(uri) => {
             writer
                 .write_event(Event::Start(BytesStart::borrowed_name(b"uri")))
                 .map_err(map_xml_error)?;
@@ -100,7 +122,7 @@ fn write_solutions(solutions: QuerySolutionIter, sink: impl Write) -> Result<(),
                 .write_event(Event::End(BytesEnd::borrowed(b"uri")))
                 .map_err(map_xml_error)?;
         }
-                Term::BlankNode(bnode) => {
+        TermRef::BlankNode(bnode) => {
             writer
                 .write_event(Event::Start(BytesStart::borrowed_name(b"bnode")))
                 .map_err(map_xml_error)?;
@@ -111,7 +133,7 @@ fn write_solutions(solutions: QuerySolutionIter, sink: impl Write) -> Result<(),
                 .write_event(Event::End(BytesEnd::borrowed(b"bnode")))
                 .map_err(map_xml_error)?;
         }
-                Term::Literal(literal) => {
+        TermRef::Literal(literal) => {
             let mut literal_tag = BytesStart::borrowed_name(b"literal");
             if let Some(language) = literal.language() {
                 literal_tag.push_attribute(("xml:lang", language));
@@ -128,21 +150,36 @@ fn write_solutions(solutions: QuerySolutionIter, sink: impl Write) -> Result<(),
                 .write_event(Event::End(BytesEnd::borrowed(b"literal")))
                 .map_err(map_xml_error)?;
         }
-            }
+        TermRef::Triple(triple) => {
             writer
-                .write_event(Event::End(BytesEnd::borrowed(b"binding")))
+                .write_event(Event::Start(BytesStart::borrowed_name(b"triple")))
                 .map_err(map_xml_error)?;
-        }
             writer
-            .write_event(Event::End(BytesEnd::borrowed(b"result")))
+                .write_event(Event::Start(BytesStart::borrowed_name(b"subject")))
                 .map_err(map_xml_error)?;
-    }
+            write_xml_term(triple.subject.as_ref().into(), writer)?;
             writer
-        .write_event(Event::End(BytesEnd::borrowed(b"results")))
+                .write_event(Event::End(BytesEnd::borrowed(b"subject")))
                 .map_err(map_xml_error)?;
             writer
-        .write_event(Event::End(BytesEnd::borrowed(b"sparql")))
+                .write_event(Event::Start(BytesStart::borrowed_name(b"predicate")))
+                .map_err(map_xml_error)?;
+            write_xml_term(triple.predicate.as_ref().into(), writer)?;
+            writer
+                .write_event(Event::End(BytesEnd::borrowed(b"predicate")))
                 .map_err(map_xml_error)?;
+            writer
+                .write_event(Event::Start(BytesStart::borrowed_name(b"object")))
+                .map_err(map_xml_error)?;
+            write_xml_term(triple.object.as_ref(), writer)?;
+            writer
+                .write_event(Event::End(BytesEnd::borrowed(b"object")))
+                .map_err(map_xml_error)?;
+            writer
+                .write_event(Event::End(BytesEnd::borrowed(b"triple")))
+                .map_err(map_xml_error)?;
+        }
+    }
     Ok(())
 }
 

lib/src/storage/binary_encoder.rs

@@ -1,10 +1,11 @@
 use crate::error::invalid_data_error;
 use crate::model::xsd::*;
-use crate::storage::numeric_encoder::{EncodedQuad, EncodedTerm, StrHash};
+use crate::storage::numeric_encoder::{EncodedQuad, EncodedTerm, EncodedTriple, StrHash};
 use crate::storage::small_string::SmallString;
 use std::io;
 use std::io::{Cursor, Read};
 use std::mem::size_of;
+use std::rc::Rc;
 
 pub const LATEST_STORAGE_VERSION: u64 = 1;
 pub const WRITTEN_TERM_MAX_SIZE: usize = size_of::<u8>() + 2 * size_of::<StrHash>();
@@ -13,7 +14,8 @@ pub const WRITTEN_TERM_MAX_SIZE: usize = size_of::<u8>() + 2 * size_of::<StrHash
 // 1-7: usual named nodes (except prefixes c.f. later)
 // 8-15: blank nodes
 // 16-47: literals
-// 48-64: future use
+// 48-55: triples
+// 56-64: future use
 // 64-127: default named node prefixes
 // 128-255: custom named node prefixes
 const TYPE_NAMED_NODE_ID: u8 = 1;
@@ -45,6 +47,7 @@ const TYPE_G_MONTH_LITERAL: u8 = 41;
 const TYPE_DURATION_LITERAL: u8 = 42;
 const TYPE_YEAR_MONTH_DURATION_LITERAL: u8 = 43;
 const TYPE_DAY_TIME_DURATION_LITERAL: u8 = 44;
+const TYPE_TRIPLE: u8 = 48;
 
 #[derive(Clone, Copy)]
 pub enum QuadEncoding {
@@ -396,6 +399,11 @@ impl<R: Read> TermReader for R {
                     DayTimeDuration::from_be_bytes(buffer),
                 ))
             }
+            TYPE_TRIPLE => Ok(EncodedTerm::Triple(Rc::new(EncodedTriple {
+                subject: self.read_term()?,
+                predicate: self.read_term()?,
+                object: self.read_term()?,
+            }))),
             _ => Err(invalid_data_error("the term buffer has an invalid type id")),
         }
     }
@@ -621,6 +629,12 @@ pub fn write_term(sink: &mut Vec<u8>, term: &EncodedTerm) {
             sink.push(TYPE_DAY_TIME_DURATION_LITERAL);
             sink.extend_from_slice(&value.to_be_bytes())
         }
+        EncodedTerm::Triple(value) => {
+            sink.push(TYPE_TRIPLE);
+            write_term(sink, &value.subject);
+            write_term(sink, &value.predicate);
+            write_term(sink, &value.object);
+        }
     }
 }
 
@@ -715,6 +729,12 @@ mod tests {
                 NamedNode::new_unchecked("http://foo.com"),
             )
             .into(),
+            Triple::new(
+                NamedNode::new_unchecked("http://foo.com"),
+                NamedNode::new_unchecked("http://bar.com"),
+                Literal::from(true),
+            )
+            .into(),
         ];
         for term in terms {
             let encoded = store.encode_term(term.as_ref()).unwrap();

lib/src/storage/numeric_encoder.rs

@@ -14,6 +14,7 @@ use std::error::Error;
 use std::fmt::Debug;
 use std::hash::Hash;
 use std::hash::Hasher;
+use std::rc::Rc;
 use std::{fmt, io, str};
 
 #[derive(Eq, PartialEq, Debug, Clone, Copy, Hash)]
@@ -101,6 +102,7 @@ pub enum EncodedTerm {
     DurationLiteral(Duration),
     YearMonthDurationLiteral(YearMonthDuration),
     DayTimeDurationLiteral(DayTimeDuration),
+    Triple(Rc<EncodedTriple>),
 }
 
 impl PartialEq for EncodedTerm {
@@ -214,6 +216,7 @@ impl PartialEq for EncodedTerm {
             (Self::DurationLiteral(a), Self::DurationLiteral(b)) => a == b,
             (Self::YearMonthDurationLiteral(a), Self::YearMonthDurationLiteral(b)) => a == b,
             (Self::DayTimeDurationLiteral(a), Self::DayTimeDurationLiteral(b)) => a == b,
+            (Self::Triple(a), Self::Triple(b)) => a == b,
             (_, _) => false,
         }
     }
@@ -277,6 +280,7 @@ impl Hash for EncodedTerm {
             Self::DurationLiteral(value) => value.hash(state),
             Self::YearMonthDurationLiteral(value) => value.hash(state),
             Self::DayTimeDurationLiteral(value) => value.hash(state),
+            Self::Triple(value) => value.hash(state),
         }
     }
 }
@@ -338,7 +342,7 @@ impl EncodedTerm {
 
     pub fn on_each_id<E>(
         &self,
-        mut callback: impl FnMut(&StrHash) -> Result<(), E>,
+        callback: &mut impl FnMut(&StrHash) -> Result<(), E>,
     ) -> Result<(), E> {
         match self {
             Self::NamedNode { iri_id } => {
@@ -373,6 +377,11 @@ impl EncodedTerm {
                 callback(value_id)?;
                 callback(datatype_id)?;
             }
+            Self::Triple(triple) => {
+                triple.subject.on_each_id(callback)?;
+                triple.predicate.on_each_id(callback)?;
+                triple.object.on_each_id(callback)?;
+            }
             _ => (),
         }
         Ok(())
@@ -462,6 +471,19 @@ impl From<DayTimeDuration> for EncodedTerm {
     }
 }
 
+impl From<EncodedTriple> for EncodedTerm {
+    fn from(value: EncodedTriple) -> Self {
+        Self::Triple(Rc::new(value))
+    }
+}
+
+#[derive(Eq, PartialEq, Debug, Clone, Hash)]
+pub struct EncodedTriple {
+    pub subject: EncodedTerm,
+    pub predicate: EncodedTerm,
+    pub object: EncodedTerm,
+}
+
 #[derive(Eq, PartialEq, Debug, Clone, Hash)]
 pub struct EncodedQuad {
     pub subject: EncodedTerm,
@@ -613,6 +635,9 @@ pub(crate) fn get_encoded_subject(term: SubjectRef<'_>) -> EncodedTerm {
     match term {
         SubjectRef::NamedNode(named_node) => get_encoded_named_node(named_node),
         SubjectRef::BlankNode(blank_node) => get_encoded_blank_node(blank_node),
+        SubjectRef::Triple(triple) => {
+            EncodedTerm::Triple(Rc::new(get_encoded_triple(triple.as_ref())))
+        }
     }
 }
 
@@ -621,6 +646,9 @@ pub(crate) fn get_encoded_term(term: TermRef<'_>) -> EncodedTerm {
         TermRef::NamedNode(named_node) => get_encoded_named_node(named_node),
         TermRef::BlankNode(blank_node) => get_encoded_blank_node(blank_node),
         TermRef::Literal(literal) => get_encoded_literal(literal),
+        TermRef::Triple(triple) => {
+            EncodedTerm::Triple(Rc::new(get_encoded_triple(triple.as_ref())))
+        }
     }
 }
 
@@ -632,6 +660,14 @@ pub(crate) fn get_encoded_graph_name(name: GraphNameRef<'_>) -> EncodedTerm {
     }
 }
 
+pub(crate) fn get_encoded_triple(quad: TripleRef<'_>) -> EncodedTriple {
+    EncodedTriple {
+        subject: get_encoded_subject(quad.subject),
+        predicate: get_encoded_named_node(quad.predicate),
+        object: get_encoded_term(quad.object),
+    }
+}
+
 pub(crate) fn get_encoded_quad(quad: QuadRef<'_>) -> EncodedQuad {
     EncodedQuad {
         subject: get_encoded_subject(quad.subject),
@@ -670,6 +706,9 @@ pub(crate) trait WriteEncoder: StrContainer {
         match term {
             SubjectRef::NamedNode(named_node) => self.encode_named_node(named_node),
             SubjectRef::BlankNode(blank_node) => self.encode_blank_node(blank_node),
+            SubjectRef::Triple(triple) => Ok(EncodedTerm::Triple(Rc::new(
+                self.encode_triple(triple.as_ref())?,
+            ))),
         }
     }
 
@@ -678,6 +717,9 @@ pub(crate) trait WriteEncoder: StrContainer {
             TermRef::NamedNode(named_node) => self.encode_named_node(named_node),
             TermRef::BlankNode(blank_node) => self.encode_blank_node(blank_node),
             TermRef::Literal(literal) => self.encode_literal(literal),
+            TermRef::Triple(triple) => Ok(EncodedTerm::Triple(Rc::new(
+                self.encode_triple(triple.as_ref())?,
+            ))),
         }
     }
 
@@ -689,6 +731,14 @@ pub(crate) trait WriteEncoder: StrContainer {
         }
     }
 
+    fn encode_triple(&self, quad: TripleRef<'_>) -> Result<EncodedTriple, Self::Error> {
+        Ok(EncodedTriple {
+            subject: self.encode_subject(quad.subject)?,
+            predicate: self.encode_named_node(quad.predicate)?,
+            object: self.encode_term(quad.object)?,
+        })
+    }
+
     fn encode_quad(&self, quad: QuadRef<'_>) -> Result<EncodedQuad, Self::Error> {
         Ok(EncodedQuad {
             subject: self.encode_subject(quad.subject)?,
@@ -980,7 +1030,10 @@ pub(crate) trait Decoder: StrLookup {
             Term::NamedNode(named_node) => Ok(named_node.into()),
             Term::BlankNode(blank_node) => Ok(blank_node.into()),
             Term::Literal(_) => Err(DecoderError::Decoder {
-                msg: "A literal has ben found instead of a named node".to_owned(),
+                msg: "A literal has been found instead of a named node".to_owned(),
+            }),
+            Term::Triple(_) => Err(DecoderError::Decoder {
+                msg: "A triple has been found instead of a named node".to_owned(),
             }),
         }
     }
@@ -995,19 +1048,44 @@ pub(crate) trait Decoder: StrLookup {
                 msg: "A blank node has been found instead of a named node".to_owned(),
             }),
             Term::Literal(_) => Err(DecoderError::Decoder {
-                msg: "A literal has ben found instead of a named node".to_owned(),
+                msg: "A literal has been found instead of a named node".to_owned(),
+            }),
+            Term::Triple(_) => Err(DecoderError::Decoder {
+                msg: "A triple has been found instead of a named node".to_owned(),
             }),
         }
     }
 
+    fn decode_triple(&self, encoded: &EncodedTriple) -> Result<Triple, DecoderError<Self::Error>> {
+        Ok(Triple::new(
+            self.decode_subject(&encoded.subject)?,
+            self.decode_named_node(&encoded.predicate)?,
+            self.decode_term(&encoded.object)?,
+        ))
+    }
+
     fn decode_quad(&self, encoded: &EncodedQuad) -> Result<Quad, DecoderError<Self::Error>> {
         Ok(Quad::new(
             self.decode_subject(&encoded.subject)?,
             self.decode_named_node(&encoded.predicate)?,
             self.decode_term(&encoded.object)?,
-            match &encoded.graph_name {
+            if encoded.graph_name == EncodedTerm::DefaultGraph {
-                EncodedTerm::DefaultGraph => None,
+                GraphName::DefaultGraph
-                graph_name => Some(self.decode_subject(graph_name)?),
+            } else {
+                match self.decode_term(&encoded.graph_name)? {
+                    Term::NamedNode(named_node) => named_node.into(),
+                    Term::BlankNode(blank_node) => blank_node.into(),
+                    Term::Literal(_) => {
+                        return Err(DecoderError::Decoder {
+                            msg: "A literal is not a valid graph name".to_owned(),
+                        })
+                    }
+                    Term::Triple(_) => {
+                        return Err(DecoderError::Decoder {
+                            msg: "A triple is not a valid graph name".to_owned(),
+                        })
+                    }
+                }
             },
         ))
     }
@@ -1089,6 +1167,7 @@ impl<S: StrLookup> Decoder for S {
             EncodedTerm::DurationLiteral(value) => Ok(Literal::from(*value).into()),
             EncodedTerm::YearMonthDurationLiteral(value) => Ok(Literal::from(*value).into()),
             EncodedTerm::DayTimeDurationLiteral(value) => Ok(Literal::from(*value).into()),
+            EncodedTerm::Triple(triple) => Ok(self.decode_triple(triple)?.into()),
         }
     }
 }

lib/src/store.rs

@@ -5,14 +5,12 @@
 //! use oxigraph::store::Store;
 //! use oxigraph::sparql::QueryResults;
 //! use oxigraph::model::*;
-//! # use std::fs::remove_dir_all;
 //!
-//! # {
+//! let store = Store::new()?;
-//! let store = Store::open("example.db")?;
 //!
 //! // insertion
 //! let ex = NamedNode::new("http://example.com")?;
-//! let quad = Quad::new(ex.clone(), ex.clone(), ex.clone(), None);
+//! let quad = Quad::new(ex.clone(), ex.clone(), ex.clone(), GraphName::DefaultGraph);
 //! store.insert(&quad)?;
 //!
 //! // quad filter
@@ -23,9 +21,6 @@
 //! if let QueryResults::Solutions(mut solutions) = store.query("SELECT ?s WHERE { ?s ?p ?o }")? {
 //!     assert_eq!(solutions.next().unwrap()?.get("s"), Some(&ex.into()));
 //! };
-//! #
-//! # };
-//! # remove_dir_all("example.db")?;
 //! # Result::<_,Box<dyn std::error::Error>>::Ok(())
 //! ```
 
@@ -69,7 +64,7 @@ use std::{fmt, io, str};
 ///
 /// // insertion
 /// let ex = NamedNode::new("http://example.com")?;
-/// let quad = Quad::new(ex.clone(), ex.clone(), ex.clone(), None);
+/// let quad = Quad::new(ex.clone(), ex.clone(), ex.clone(), GraphName::DefaultGraph);
 /// store.insert(&quad)?;
 ///
 /// // quad filter
@@ -119,7 +114,7 @@ impl Store {
     ///
     /// // insertions
     /// let ex = NamedNodeRef::new("http://example.com")?;
-    /// store.insert(QuadRef::new(ex, ex, ex, None))?;
+    /// store.insert(QuadRef::new(ex, ex, ex, GraphNameRef::DefaultGraph))?;
     ///
     /// // SPARQL query
     /// if let QueryResults::Solutions(mut solutions) =  store.query("SELECT ?s WHERE { ?s ?p ?o }")? {
@@ -154,7 +149,7 @@ impl Store {
     ///
     /// // insertion
     /// let ex = NamedNode::new("http://example.com")?;
-    /// let quad = Quad::new(ex.clone(), ex.clone(), ex.clone(), None);
+    /// let quad = Quad::new(ex.clone(), ex.clone(), ex.clone(), GraphName::DefaultGraph);
     /// store.insert(&quad)?;
     ///
     /// // quad filter by object
@@ -220,7 +215,7 @@ impl Store {
     ///
     /// // we inspect the store contents
     /// let ex = NamedNodeRef::new("http://example.com").unwrap();
-    /// assert!(store.contains(QuadRef::new(ex, ex, ex, None))?);
+    /// assert!(store.contains(QuadRef::new(ex, ex, ex, GraphNameRef::DefaultGraph))?);
     /// # Result::<_,Box<dyn std::error::Error>>::Ok(())
     /// ```
     pub fn update(
@@ -298,7 +293,7 @@ impl Store {
     ///
     /// // we inspect the store contents
     /// let ex = NamedNodeRef::new("http://example.com")?;
-    /// assert!(store.contains(QuadRef::new(ex, ex, ex, None))?);
+    /// assert!(store.contains(QuadRef::new(ex, ex, ex, GraphNameRef::DefaultGraph))?);
     /// # Result::<_,Box<dyn std::error::Error>>::Ok(())
     /// ```
     ///
@@ -441,12 +436,12 @@ impl Store {
     /// Usage example:
     /// ```
     /// use oxigraph::store::Store;
-    /// use oxigraph::model::{NamedNode, QuadRef, Subject};
+    /// use oxigraph::model::*;
     ///
     /// let ex = NamedNode::new("http://example.com")?;
     /// let store = Store::new()?;
     /// store.insert(QuadRef::new(&ex, &ex, &ex, &ex))?;
-    /// store.insert(QuadRef::new(&ex, &ex, &ex, None))?;
+    /// store.insert(QuadRef::new(&ex, &ex, &ex, GraphNameRef::DefaultGraph))?;
     /// assert_eq!(vec![Subject::from(ex)], store.named_graphs().collect::<Result<Vec<_>,_>>()?);
     /// # Result::<_,Box<dyn std::error::Error>>::Ok(())
     /// ```
@@ -560,12 +555,12 @@ impl Store {
     /// Usage example:
     /// ```
     /// use oxigraph::store::Store;
-    /// use oxigraph::model::{NamedNodeRef, QuadRef};
+    /// use oxigraph::model::*;
     ///
     /// let ex = NamedNodeRef::new("http://example.com")?;
     /// let store = Store::new()?;
     /// store.insert(QuadRef::new(ex, ex, ex, ex))?;
-    /// store.insert(QuadRef::new(ex, ex, ex, None))?;    
+    /// store.insert(QuadRef::new(ex, ex, ex, GraphNameRef::DefaultGraph))?;    
     /// assert_eq!(2, store.len());
     ///
     /// store.clear()?;
@@ -616,7 +611,7 @@ impl Transaction<'_> {
     ///
     /// // we inspect the store content
     /// let ex = NamedNodeRef::new("http://example.com")?;
-    /// assert!(store.contains(QuadRef::new(ex, ex, ex, None))?);
+    /// assert!(store.contains(QuadRef::new(ex, ex, ex, GraphNameRef::DefaultGraph))?);
     /// # Result::<_, Box<dyn std::error::Error>>::Ok(())
     /// ```
     ///
@@ -769,7 +764,12 @@ fn store() -> Result<(), io::Error> {
     let main_o = Term::from(Literal::from(1));
     let main_g = GraphName::from(BlankNode::default());
 
-    let default_quad = Quad::new(main_s.clone(), main_p.clone(), main_o.clone(), None);
+    let default_quad = Quad::new(
+        main_s.clone(),
+        main_p.clone(),
+        main_o.clone(),
+        GraphName::DefaultGraph,
+    );
     let named_quad = Quad::new(
         main_s.clone(),
         main_p.clone(),
@@ -777,23 +777,33 @@ fn store() -> Result<(), io::Error> {
         main_g.clone(),
     );
     let default_quads = vec![
-        Quad::new(main_s.clone(), main_p.clone(), Literal::from(0), None),
+        Quad::new(
+            main_s.clone(),
+            main_p.clone(),
+            Literal::from(0),
+            GraphName::DefaultGraph,
+        ),
         default_quad.clone(),
         Quad::new(
             main_s.clone(),
             main_p.clone(),
             Literal::from(200000000),
-            None,
+            GraphName::DefaultGraph,
         ),
     ];
     let all_quads = vec![
-        Quad::new(main_s.clone(), main_p.clone(), Literal::from(0), None),
+        Quad::new(
+            main_s.clone(),
+            main_p.clone(),
+            Literal::from(0),
+            GraphName::DefaultGraph,
+        ),
         default_quad.clone(),
         Quad::new(
             main_s.clone(),
             main_p.clone(),
             Literal::from(200000000),
-            None,
+            GraphName::DefaultGraph,
         ),
         named_quad.clone(),
     ];

lib/tests/store.rs

@@ -78,7 +78,12 @@ fn quads(graph_name: impl Into<GraphNameRef<'static>>) -> Vec<QuadRef<'static>>
 #[test]
 fn test_load_graph() -> io::Result<()> {
     let store = Store::new()?;
-    store.load_graph(Cursor::new(DATA), GraphFormat::Turtle, None, None)?;
+    store.load_graph(
+        Cursor::new(DATA),
+        GraphFormat::Turtle,
+        GraphNameRef::DefaultGraph,
+        None,
+    )?;
     for q in quads(GraphNameRef::DefaultGraph) {
         assert!(store.contains(q)?);
     }
@@ -103,7 +108,11 @@ fn test_dump_graph() -> io::Result<()> {
     }
 
     let mut buffer = Vec::new();
-    store.dump_graph(&mut buffer, GraphFormat::NTriples, None)?;
+    store.dump_graph(
+        &mut buffer,
+        GraphFormat::NTriples,
+        GraphNameRef::DefaultGraph,
+    )?;
     assert_eq!(
         buffer.into_iter().filter(|c| *c == b'\n').count(),
         NUMBER_OF_TRIPLES
@@ -131,7 +140,12 @@ fn test_dump_dataset() -> io::Result<()> {
 fn test_transaction_load_graph() -> io::Result<()> {
     let store = Store::new()?;
     store.transaction(|t| {
-        t.load_graph(Cursor::new(DATA), GraphFormat::Turtle, None, None)?;
+        t.load_graph(
+            Cursor::new(DATA),
+            GraphFormat::Turtle,
+            GraphNameRef::DefaultGraph,
+            None,
+        )?;
         Ok(()) as Result<_, ConflictableTransactionError<io::Error>>
     })?;
     for q in quads(GraphNameRef::DefaultGraph) {

python/src/model.rs

@@ -408,6 +408,7 @@ impl PyObjectProtocol for PyDefaultGraph {
 pub enum PySubject {
     NamedNode(PyNamedNode),
     BlankNode(PyBlankNode),
+    Triple(PyTriple),
 }
 
 impl From<PySubject> for Subject {
@@ -415,6 +416,7 @@ impl From<PySubject> for Subject {
         match node {
             PySubject::NamedNode(node) => node.into(),
             PySubject::BlankNode(node) => node.into(),
+            PySubject::Triple(triple) => triple.into(),
         }
     }
 }
@@ -424,6 +426,7 @@ impl From<Subject> for PySubject {
         match node {
             Subject::NamedNode(node) => PySubject::NamedNode(node.into()),
             Subject::BlankNode(node) => PySubject::BlankNode(node.into()),
+            Subject::Triple(triple) => PySubject::Triple(triple.as_ref().clone().into()),
         }
     }
 }
@@ -433,6 +436,7 @@ impl IntoPy<PyObject> for PySubject {
         match self {
             PySubject::NamedNode(node) => node.into_py(py),
             PySubject::BlankNode(node) => node.into_py(py),
+            PySubject::Triple(triple) => triple.into_py(py),
         }
     }
 }
@@ -442,6 +446,7 @@ pub enum PyTerm {
     NamedNode(PyNamedNode),
     BlankNode(PyBlankNode),
     Literal(PyLiteral),
+    Triple(PyTriple),
 }
 
 impl From<PyTerm> for Term {
@@ -450,6 +455,7 @@ impl From<PyTerm> for Term {
             PyTerm::NamedNode(node) => node.into(),
             PyTerm::BlankNode(node) => node.into(),
             PyTerm::Literal(literal) => literal.into(),
+            PyTerm::Triple(triple) => triple.into(),
         }
     }
 }
@@ -460,6 +466,7 @@ impl From<Term> for PyTerm {
             Term::NamedNode(node) => PyTerm::NamedNode(node.into()),
             Term::BlankNode(node) => PyTerm::BlankNode(node.into()),
             Term::Literal(literal) => PyTerm::Literal(literal.into()),
+            Term::Triple(triple) => PyTerm::Triple(triple.as_ref().clone().into()),
         }
     }
 }
@@ -470,6 +477,7 @@ impl IntoPy<PyObject> for PyTerm {
             PyTerm::NamedNode(node) => node.into_py(py),
             PyTerm::BlankNode(node) => node.into_py(py),
             PyTerm::Literal(literal) => literal.into_py(py),
+            PyTerm::Triple(triple) => triple.into_py(py),
         }
     }
 }
@@ -505,14 +513,26 @@ impl From<Triple> for PyTriple {
 }
 
 impl From<PyTriple> for Triple {
-    fn from(node: PyTriple) -> Self {
+    fn from(triple: PyTriple) -> Self {
-        node.inner
+        triple.inner
     }
 }
 
 impl<'a> From<&'a PyTriple> for TripleRef<'a> {
-    fn from(node: &'a PyTriple) -> Self {
+    fn from(triple: &'a PyTriple) -> Self {
-        node.inner.as_ref()
+        triple.inner.as_ref()
+    }
+}
+
+impl From<PyTriple> for Subject {
+    fn from(triple: PyTriple) -> Self {
+        triple.inner.into()
+    }
+}
+
+impl From<PyTriple> for Term {
+    fn from(triple: PyTriple) -> Self {
+        triple.inner.into()
     }
 }
 
@@ -562,13 +582,7 @@ impl PyObjectProtocol for PyTriple {
 
     fn __repr__(&self) -> String {
         let mut buffer = String::new();
-        buffer.push_str("<Triple subject=");
+        triple_repr(self.inner.as_ref(), &mut buffer);
-        term_repr(self.inner.subject.as_ref().into(), &mut buffer);
-        buffer.push_str(" predicate=");
-        named_node_repr(self.inner.predicate.as_ref(), &mut buffer);
-        buffer.push_str(" object=");
-        term_repr(self.inner.object.as_ref(), &mut buffer);
-        buffer.push('>');
         buffer
     }
 
@@ -1109,6 +1123,7 @@ pub fn term_repr(term: TermRef<'_>, buffer: &mut String) {
         TermRef::NamedNode(node) => named_node_repr(node, buffer),
         TermRef::BlankNode(node) => blank_node_repr(node, buffer),
         TermRef::Literal(literal) => literal_repr(literal, buffer),
+        TermRef::Triple(triple) => triple_repr(triple.as_ref(), buffer),
     }
 }
 
@@ -1120,6 +1135,16 @@ fn graph_name_repr(term: GraphNameRef<'_>, buffer: &mut String) {
     }
 }
 
+fn triple_repr(triple: TripleRef<'_>, buffer: &mut String) {
+    buffer.push_str("<Triple subject=");
+    term_repr(triple.subject.into(), buffer);
+    buffer.push_str(" predicate=");
+    named_node_repr(triple.predicate, buffer);
+    buffer.push_str(" object=");
+    term_repr(triple.object, buffer);
+    buffer.push('>');
+}
+
 #[pyclass(module = "oxigraph")]
 pub struct TripleComponentsIter {
     inner: IntoIter<Term>,

python/tests/test_model.py

@@ -76,6 +76,31 @@ class TestTriple(unittest.TestCase):
         self.assertEqual(t.predicate, NamedNode("http://example.com/p"))
         self.assertEqual(t.object, NamedNode("http://example.com/o"))
 
+    def test_rdf_star_constructor(self):
+        t = Triple(
+            Triple(
+                NamedNode("http://example.com/ss"),
+                NamedNode("http://example.com/sp"),
+                NamedNode("http://example.com/so")
+            ),
+            NamedNode("http://example.com/p"),
+            Triple(
+                NamedNode("http://example.com/os"),
+                NamedNode("http://example.com/op"),
+                NamedNode("http://example.com/oo")
+            ), )
+        self.assertEqual(t.subject, Triple(
+            NamedNode("http://example.com/ss"),
+            NamedNode("http://example.com/sp"),
+            NamedNode("http://example.com/so")
+        ))
+        self.assertEqual(t.predicate, NamedNode("http://example.com/p"))
+        self.assertEqual(t.object, Triple(
+            NamedNode("http://example.com/os"),
+            NamedNode("http://example.com/op"),
+            NamedNode("http://example.com/oo")
+        ))
+
     def test_mapping(self):
         t = Triple(
             NamedNode("http://example.com/s"),

python/tests/test_store.py

@@ -6,6 +6,7 @@ from pyoxigraph import *
 foo = NamedNode("http://foo")
 bar = NamedNode("http://bar")
 baz = NamedNode("http://baz")
+triple = Triple(foo, foo, foo)
 graph = NamedNode("http://graph")
 
 
@@ -15,7 +16,9 @@ class TestStore(unittest.TestCase):
         store.add(Quad(foo, bar, baz))
         store.add(Quad(foo, bar, baz, DefaultGraph()))
         store.add(Quad(foo, bar, baz, graph))
-        self.assertEqual(len(store), 2)
+        store.add(Quad(triple, bar, baz))
+        store.add(Quad(foo, bar, triple))
+        self.assertEqual(len(store), 4)
 
     def test_remove(self):
         store = Store()