Creates a simplistic implementation of a MemoryStore

Moves the graph isomorphism implementation out of rdf_test_cases

src/lib.rs

@@ -4,3 +4,4 @@ extern crate url;
 
 pub mod model;
 pub mod rio;
+pub mod store;

src/store/isomorphism.rs

@@ -0,0 +1,154 @@
+use model::data::*;
+use std::collections::BTreeSet;
+use std::collections::HashMap;
+use std::collections::HashSet;
+use std::collections::hash_map::DefaultHasher;
+use std::hash::Hash;
+use std::hash::Hasher;
+use store::memory::MemoryGraph;
+
+#[derive(Eq, PartialEq, Hash, Ord, PartialOrd)]
+struct SubjectPredicate<'a> {
+    subject: &'a NamedOrBlankNode,
+    predicate: &'a NamedNode,
+}
+
+impl<'a> SubjectPredicate<'a> {
+    fn new(subject: &'a NamedOrBlankNode, predicate: &'a NamedNode) -> Self {
+        Self { subject, predicate }
+    }
+}
+
+#[derive(Eq, PartialEq, Hash, Ord, PartialOrd)]
+struct PredicateObject<'a> {
+    predicate: &'a NamedNode,
+    object: &'a Term,
+}
+
+impl<'a> PredicateObject<'a> {
+    fn new(predicate: &'a NamedNode, object: &'a Term) -> Self {
+        Self { predicate, object }
+    }
+}
+
+fn subject_predicates_for_object<'a>(
+    graph: &'a MemoryGraph,
+    object: &'a Term,
+) -> impl Iterator<Item = SubjectPredicate<'a>> {
+    graph
+        .triples_for_object(object)
+        .map(|t| SubjectPredicate::new(t.subject(), t.predicate()))
+}
+
+fn predicate_objects_for_subject<'a>(
+    graph: &'a MemoryGraph,
+    subject: &'a NamedOrBlankNode,
+) -> impl Iterator<Item = PredicateObject<'a>> {
+    graph
+        .triples_for_subject(subject)
+        .map(|t| PredicateObject::new(t.predicate(), t.object()))
+}
+
+fn hash_blank_nodes<'a>(
+    bnodes: HashSet<&'a BlankNode>,
+    graph: &'a MemoryGraph,
+) -> HashMap<u64, Vec<&'a BlankNode>> {
+    let mut bnodes_by_hash: HashMap<u64, Vec<&BlankNode>> = HashMap::default();
+
+    // NB: we need to sort the triples to have the same hash
+    for bnode in bnodes.into_iter() {
+        let mut hasher = DefaultHasher::new();
+
+        {
+            let subject = NamedOrBlankNode::from(bnode.clone());
+            let mut po_set: BTreeSet<PredicateObject> = BTreeSet::default();
+            for po in predicate_objects_for_subject(&graph, &subject) {
+                if !po.object.is_blank_node() {
+                    po_set.insert(po);
+                }
+            }
+            for po in po_set {
+                po.hash(&mut hasher);
+            }
+        }
+
+        {
+            let object = Term::from(bnode.clone());
+            let mut sp_set: BTreeSet<SubjectPredicate> = BTreeSet::default();
+            for sp in subject_predicates_for_object(&graph, &object) {
+                if !sp.subject.is_blank_node() {
+                    sp_set.insert(sp);
+                }
+            }
+            for sp in sp_set {
+                sp.hash(&mut hasher);
+            }
+        }
+
+        bnodes_by_hash
+            .entry(hasher.finish())
+            .or_insert_with(Vec::default)
+            .push(bnode);
+    }
+
+    bnodes_by_hash
+}
+
+pub trait GraphIsomorphism {
+    /// Checks if two graphs are [isomorphic](https://www.w3.org/TR/rdf11-concepts/#dfn-graph-isomorphism)
+    fn is_isomorphic(&self, other: &Self) -> bool;
+}
+
+impl GraphIsomorphism for MemoryGraph {
+    //TODO: proper isomorphism building
+    fn is_isomorphic(&self, other: &Self) -> bool {
+        if self.len() != other.len() {
+            return false;
+        }
+
+        let mut self_bnodes: HashSet<&BlankNode> = HashSet::default();
+        let mut other_bnodes: HashSet<&BlankNode> = HashSet::default();
+
+        for t in self {
+            if let NamedOrBlankNode::BlankNode(subject) = t.subject() {
+                self_bnodes.insert(subject);
+                if let Term::BlankNode(object) = t.object() {
+                    self_bnodes.insert(object);
+                }
+            } else if let Term::BlankNode(object) = t.object() {
+                self_bnodes.insert(object);
+            } else if !other.contains(t) {
+                return false;
+            }
+        }
+        for t in other {
+            if let NamedOrBlankNode::BlankNode(subject) = t.subject() {
+                other_bnodes.insert(subject);
+                if let Term::BlankNode(object) = t.object() {
+                    other_bnodes.insert(object);
+                }
+            } else if let Term::BlankNode(object) = t.object() {
+                other_bnodes.insert(object);
+            } else if !self.contains(t) {
+                return false;
+            }
+        }
+
+        let self_bnodes_by_hash = hash_blank_nodes(self_bnodes, &self);
+        let other_bnodes_by_hash = hash_blank_nodes(other_bnodes, &other);
+
+        if self_bnodes_by_hash.len() != other_bnodes_by_hash.len() {
+            return false;
+        }
+
+        for hash in self_bnodes_by_hash.keys() {
+            if self_bnodes_by_hash.get(hash).map(|l| l.len())
+                != other_bnodes_by_hash.get(hash).map(|l| l.len())
+            {
+                return false;
+            }
+        }
+
+        true
+    }
+}

src/store/memory.rs

@@ -0,0 +1,148 @@
+use model::data::*;
+use std::collections::HashSet;
+use std::fmt;
+use std::iter::FromIterator;
+
+#[derive(Debug, Clone, Default)]
+pub struct MemoryGraph {
+    triples: HashSet<Triple>,
+}
+
+impl MemoryGraph {
+    pub fn iter(&self) -> impl Iterator<Item = &Triple> {
+        self.triples.iter()
+    }
+
+    pub fn triples_for_subject<'a>(
+        &'a self,
+        subject: &'a NamedOrBlankNode,
+    ) -> impl Iterator<Item = &'a Triple> {
+        self.iter().filter(move |t| t.subject() == subject)
+    }
+
+    pub fn triples_for_predicate<'a>(
+        &'a self,
+        predicate: &'a NamedNode,
+    ) -> impl Iterator<Item = &'a Triple> {
+        self.iter().filter(move |t| t.predicate() == predicate)
+    }
+
+    pub fn triples_for_object<'a>(&'a self, object: &'a Term) -> impl Iterator<Item = &'a Triple> {
+        self.iter().filter(move |t| t.object() == object)
+    }
+
+    pub fn triples_for_subject_predicate<'a>(
+        &'a self,
+        subject: &'a NamedOrBlankNode,
+        predicate: &'a NamedNode,
+    ) -> impl Iterator<Item = &'a Triple> {
+        self.iter()
+            .filter(move |t| t.subject() == subject && t.predicate() == predicate)
+    }
+
+    pub fn objects_for_subject_predicate<'a>(
+        &'a self,
+        subject: &'a NamedOrBlankNode,
+        predicate: &'a NamedNode,
+    ) -> impl Iterator<Item = &'a Term> {
+        self.triples_for_subject_predicate(subject, predicate)
+            .map(|t| t.object())
+    }
+
+    pub fn object_for_subject_predicate<'a>(
+        &'a self,
+        subject: &'a NamedOrBlankNode,
+        predicate: &'a NamedNode,
+    ) -> Option<&'a Term> {
+        self.objects_for_subject_predicate(subject, predicate)
+            .nth(0)
+    }
+
+    pub fn triples_for_predicate_object<'a>(
+        &'a self,
+        predicate: &'a NamedNode,
+        object: &'a Term,
+    ) -> impl Iterator<Item = &'a Triple> {
+        self.iter()
+            .filter(move |t| t.predicate() == predicate && t.object() == object)
+    }
+
+    pub fn subjects_for_predicate_object<'a>(
+        &'a self,
+        predicate: &'a NamedNode,
+        object: &'a Term,
+    ) -> impl Iterator<Item = &'a NamedOrBlankNode> {
+        self.triples_for_predicate_object(predicate, object)
+            .map(|t| t.subject())
+    }
+
+    pub fn subject_for_predicate_object<'a>(
+        &'a self,
+        predicate: &'a NamedNode,
+        object: &'a Term,
+    ) -> Option<&'a NamedOrBlankNode> {
+        self.subjects_for_predicate_object(predicate, object).nth(0)
+    }
+
+    pub fn len(&self) -> usize {
+        self.triples.len()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.triples.is_empty()
+    }
+
+    pub fn contains(&self, value: &Triple) -> bool {
+        self.triples.contains(value)
+    }
+
+    pub fn insert(&mut self, value: Triple) -> bool {
+        self.triples.insert(value)
+    }
+}
+
+impl fmt::Display for MemoryGraph {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        for triple in &self.triples {
+            write!(fmt, "{}\n", triple)?;
+        }
+        Ok(())
+    }
+}
+
+impl IntoIterator for MemoryGraph {
+    type Item = Triple;
+    type IntoIter = <HashSet<Triple> as IntoIterator>::IntoIter;
+
+    fn into_iter(self) -> <Self as IntoIterator>::IntoIter {
+        self.triples.into_iter()
+    }
+}
+
+impl<'a> IntoIterator for &'a MemoryGraph {
+    type Item = &'a Triple;
+    type IntoIter = <&'a HashSet<Triple> as IntoIterator>::IntoIter;
+
+    fn into_iter(self) -> <Self as IntoIterator>::IntoIter {
+        self.triples.iter()
+    }
+}
+
+impl FromIterator<Triple> for MemoryGraph {
+    fn from_iter<I: IntoIterator<Item = Triple>>(iter: I) -> Self {
+        let triples = HashSet::from_iter(iter);
+        Self { triples }
+    }
+}
+
+impl Extend<Triple> for MemoryGraph {
+    fn extend<I: IntoIterator<Item = Triple>>(&mut self, iter: I) {
+        self.triples.extend(iter)
+    }
+}
+
+impl<'a> Extend<&'a Triple> for MemoryGraph {
+    fn extend<I: IntoIterator<Item = &'a Triple>>(&mut self, iter: I) {
+        self.triples.extend(iter.into_iter().cloned())
+    }
+}

src/store/mod.rs

@@ -0,0 +1,2 @@
+pub mod isomorphism;
+pub mod memory;

tests/rdf_test_cases.rs

@@ -9,13 +9,8 @@ use rudf::rio::RioError;
 use rudf::rio::RioResult;
 use rudf::rio::ntriples::read_ntriples;
 use rudf::rio::turtle::read_turtle;
-use std::collections::BTreeSet;
-use std::collections::HashMap;
-use std::collections::HashSet;
-use std::collections::hash_map::DefaultHasher;
-use std::fmt;
-use std::hash::Hash;
-use std::hash::Hasher;
+use rudf::store::isomorphism::GraphIsomorphism;
+use rudf::store::memory::MemoryGraph;
 use std::iter::FromIterator;
 use std::str::FromStr;
 use url::Url;
@@ -33,14 +28,14 @@ impl Default for RDFClient {
 }
 
 impl RDFClient {
-    fn load_turtle(&self, uri: Url) -> RioResult<HashSet<Triple>> {
+    fn load_turtle(&self, uri: Url) -> RioResult<MemoryGraph> {
         match self.client.get(uri.clone()).send() {
-            Ok(response) => Ok(HashSet::from_iter(read_turtle(response, Some(uri))?)),
+            Ok(response) => Ok(MemoryGraph::from_iter(read_turtle(response, Some(uri))?)),
             Err(error) => Err(RioError::new(error)),
         }
     }
 
-    fn load_ntriples(&self, uri: Url) -> RioResult<HashSet<Triple>> {
+    fn load_ntriples(&self, uri: Url) -> RioResult<MemoryGraph> {
         match self.client.get(uri).send() {
             Ok(response) => read_ntriples(response).collect(),
             Err(error) => Err(RioError::new(error)),
@@ -48,199 +43,6 @@ impl RDFClient {
     }
 }
 
-#[derive(Eq, PartialEq, Clone)]
-struct Graph(HashSet<Triple>);
-
-impl fmt::Display for Graph {
-    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-        for triple in &self.0 {
-            write!(fmt, "{}\n", triple)?;
-        }
-        Ok(())
-    }
-}
-
-#[derive(Eq, PartialEq, Hash, Ord, PartialOrd)]
-struct SubjectPredicate<'a> {
-    subject: &'a NamedOrBlankNode,
-    predicate: &'a NamedNode,
-}
-
-impl<'a> SubjectPredicate<'a> {
-    fn new(subject: &'a NamedOrBlankNode, predicate: &'a NamedNode) -> Self {
-        Self { subject, predicate }
-    }
-}
-
-#[derive(Eq, PartialEq, Hash, Ord, PartialOrd)]
-struct PredicateObject<'a> {
-    predicate: &'a NamedNode,
-    object: &'a Term,
-}
-
-impl<'a> PredicateObject<'a> {
-    fn new(predicate: &'a NamedNode, object: &'a Term) -> Self {
-        Self { predicate, object }
-    }
-}
-
-fn objects_for_subject_predicate<'a>(
-    graph: &'a HashSet<Triple>,
-    subject: &'a NamedOrBlankNode,
-    predicate: &'a NamedNode,
-) -> impl Iterator<Item = &'a Term> {
-    graph
-        .iter()
-        .filter(move |t| t.subject() == subject && t.predicate() == predicate)
-        .map(|t| t.object())
-}
-
-fn object_for_subject_predicate<'a>(
-    graph: &'a HashSet<Triple>,
-    subject: &'a NamedOrBlankNode,
-    predicate: &'a NamedNode,
-) -> Option<&'a Term> {
-    objects_for_subject_predicate(graph, subject, predicate).nth(0)
-}
-
-fn subjects_for_predicate_object<'a>(
-    graph: &'a HashSet<Triple>,
-    predicate: &'a NamedNode,
-    object: &'a Term,
-) -> impl Iterator<Item = &'a NamedOrBlankNode> {
-    graph
-        .iter()
-        .filter(move |t| t.predicate() == predicate && t.object() == object)
-        .map(|t| t.subject())
-}
-
-fn subject_for_predicate_object<'a>(
-    graph: &'a HashSet<Triple>,
-    predicate: &'a NamedNode,
-    object: &'a Term,
-) -> Option<&'a NamedOrBlankNode> {
-    subjects_for_predicate_object(graph, predicate, object).nth(0)
-}
-
-fn subject_predicates_for_object<'a>(
-    graph: &'a HashSet<Triple>,
-    object: &'a Term,
-) -> impl Iterator<Item = SubjectPredicate<'a>> {
-    graph
-        .iter()
-        .filter(move |t| t.object() == object)
-        .map(|t| SubjectPredicate::new(t.subject(), t.predicate()))
-}
-
-fn predicate_objects_for_subject<'a>(
-    graph: &'a HashSet<Triple>,
-    subject: &'a NamedOrBlankNode,
-) -> impl Iterator<Item = PredicateObject<'a>> {
-    graph
-        .iter()
-        .filter(move |t| t.subject() == subject)
-        .map(|t| PredicateObject::new(t.predicate(), t.object()))
-}
-
-fn hash_blank_nodes<'a>(
-    bnodes: HashSet<&'a BlankNode>,
-    graph: &'a HashSet<Triple>,
-) -> HashMap<u64, Vec<&'a BlankNode>> {
-    let mut bnodes_by_hash: HashMap<u64, Vec<&BlankNode>> = HashMap::default();
-
-    // NB: we need to sort the triples to have the same hash
-    for bnode in bnodes.into_iter() {
-        let mut hasher = DefaultHasher::new();
-
-        {
-            let subject = NamedOrBlankNode::from(bnode.clone());
-            let mut po_set: BTreeSet<PredicateObject> = BTreeSet::default();
-            for po in predicate_objects_for_subject(&graph, &subject) {
-                if !po.object.is_blank_node() {
-                    po_set.insert(po);
-                }
-            }
-            for po in po_set {
-                po.hash(&mut hasher);
-            }
-        }
-
-        {
-            let object = Term::from(bnode.clone());
-            let mut sp_set: BTreeSet<SubjectPredicate> = BTreeSet::default();
-            for sp in subject_predicates_for_object(&graph, &object) {
-                if !sp.subject.is_blank_node() {
-                    sp_set.insert(sp);
-                }
-            }
-            for sp in sp_set {
-                sp.hash(&mut hasher);
-            }
-        }
-
-        bnodes_by_hash
-            .entry(hasher.finish())
-            .or_insert_with(Vec::default)
-            .push(bnode);
-    }
-
-    bnodes_by_hash
-}
-
-//TODO: use a better datastructure
-fn is_isomorphic(a: &HashSet<Triple>, b: &HashSet<Triple>) -> bool {
-    if a.len() != b.len() {
-        return false;
-    }
-
-    let mut a_bnodes: HashSet<&BlankNode> = HashSet::default();
-    let mut b_bnodes: HashSet<&BlankNode> = HashSet::default();
-
-    for t in a {
-        if let NamedOrBlankNode::BlankNode(subject) = t.subject() {
-            a_bnodes.insert(subject);
-            if let Term::BlankNode(object) = t.object() {
-                a_bnodes.insert(object);
-            }
-        } else if let Term::BlankNode(object) = t.object() {
-            a_bnodes.insert(object);
-        } else if !b.contains(t) {
-            return false;
-        }
-    }
-    for t in b {
-        if let NamedOrBlankNode::BlankNode(subject) = t.subject() {
-            b_bnodes.insert(subject);
-            if let Term::BlankNode(object) = t.object() {
-                b_bnodes.insert(object);
-            }
-        } else if let Term::BlankNode(object) = t.object() {
-            b_bnodes.insert(object);
-        } else if !a.contains(t) {
-            return false;
-        }
-    }
-
-    let a_bnodes_by_hash = hash_blank_nodes(a_bnodes, &a);
-    let b_bnodes_by_hash = hash_blank_nodes(b_bnodes, &b);
-
-    if a_bnodes_by_hash.len() != b_bnodes_by_hash.len() {
-        return false;
-    }
-
-    for hash in a_bnodes_by_hash.keys() {
-        if a_bnodes_by_hash.get(hash).map(|l| l.len())
-            != b_bnodes_by_hash.get(hash).map(|l| l.len())
-        {
-            return false;
-        }
-    }
-
-    //TODO: proper isomorphism building
-
-    true
-}
-
 #[test]
 fn turtle_w3c_testsuite() {
     let manifest_url = Url::parse("http://www.w3.org/2013/TurtleTests/manifest.ttl").unwrap();
@@ -289,11 +91,14 @@ fn turtle_w3c_testsuite() {
         ).into(),
     ];
 
-    subjects_for_predicate_object(&manifest, &rdf::TYPE, &rdft_test_turtle_positive_syntax)
+    manifest
+        .subjects_for_predicate_object(&rdf::TYPE, &rdft_test_turtle_positive_syntax)
         .for_each(|test| {
-            let comment = object_for_subject_predicate(&manifest, test, &rdfs_comment).unwrap();
+            let comment = manifest
+                .object_for_subject_predicate(test, &rdfs_comment)
+                .unwrap();
             if let Some(Term::NamedNode(file)) =
-                object_for_subject_predicate(&manifest, test, &mf_action)
+                manifest.object_for_subject_predicate(test, &mf_action)
             {
                 if let Err(error) = client.load_turtle(file.url().clone()) {
                     assert!(
@@ -304,11 +109,14 @@ fn turtle_w3c_testsuite() {
                 }
             }
         });
-    subjects_for_predicate_object(&manifest, &rdf::TYPE, &rdft_test_turtle_negative_syntax)
+    manifest
+        .subjects_for_predicate_object(&rdf::TYPE, &rdft_test_turtle_negative_syntax)
         .for_each(|test| {
-            let comment = object_for_subject_predicate(&manifest, test, &rdfs_comment).unwrap();
+            let comment = manifest
+                .object_for_subject_predicate(test, &rdfs_comment)
+                .unwrap();
             if let Some(Term::NamedNode(file)) =
-                object_for_subject_predicate(&manifest, test, &mf_action)
+                manifest.object_for_subject_predicate(test, &mf_action)
             {
                 assert!(
                     client.load_turtle(file.url().clone()).is_err(),
@@ -318,27 +126,31 @@ fn turtle_w3c_testsuite() {
                 );
             }
         });
-    subjects_for_predicate_object(&manifest, &rdf::TYPE, &rdft_test_turtle_eval).for_each(|test| {
+    manifest
+        .subjects_for_predicate_object(&rdf::TYPE, &rdft_test_turtle_eval)
+        .for_each(|test| {
             if test_blacklist.contains(test) {
                 return;
             }
-        let comment = object_for_subject_predicate(&manifest, test, &rdfs_comment).unwrap();
+            let comment = manifest
+                .object_for_subject_predicate(test, &rdfs_comment)
+                .unwrap();
             if let Some(Term::NamedNode(input)) =
-            object_for_subject_predicate(&manifest, test, &mf_action)
+                manifest.object_for_subject_predicate(test, &mf_action)
             {
                 if let Some(Term::NamedNode(result)) =
-                object_for_subject_predicate(&manifest, test, &mf_result)
+                    manifest.object_for_subject_predicate(test, &mf_result)
                 {
                     match client.load_turtle(input.url().clone()) {
                     Ok(action_graph) =>  match client.load_turtle(result.url().clone()) {
                         Ok(result_graph) => assert!(
-                            is_isomorphic(&action_graph, &result_graph),
+                            action_graph.is_isomorphic(&result_graph),
                             "Failure on positive evaluation test file {} against {} about {}. Expected file:\n{}\nParsed file:\n{}\n",
                             input,
                             result,
                             comment,
-                            Graph(action_graph),
-                            Graph(result_graph)
+                            action_graph,
+                            result_graph
                         ),
                         Err(error) => assert!(
                             false,
@@ -355,27 +167,29 @@ fn turtle_w3c_testsuite() {
                 }
             }
         });
-    subjects_for_predicate_object(&manifest, &rdf::TYPE, &rdft_test_turtle_negative_eval).for_each(
-        |test| {
-            let comment = object_for_subject_predicate(&manifest, test, &rdfs_comment).unwrap();
+    manifest
+        .subjects_for_predicate_object(&rdf::TYPE, &rdft_test_turtle_negative_eval)
+        .for_each(|test| {
+            let comment = manifest
+                .object_for_subject_predicate(test, &rdfs_comment)
+                .unwrap();
             if let Some(Term::NamedNode(file)) =
-                object_for_subject_predicate(&manifest, test, &mf_action)
+                manifest.object_for_subject_predicate(test, &mf_action)
             {
                 if let Some(Term::NamedNode(result)) =
-                    object_for_subject_predicate(&manifest, test, &mf_result)
+                    manifest.object_for_subject_predicate(test, &mf_result)
                 {
                     let action_graph = client.load_turtle(file.url().clone());
                     let result_graph = client.load_turtle(result.url().clone());
                     assert!(
-                        !is_isomorphic(&action_graph.unwrap(), &result_graph.unwrap()),
+                        !action_graph.unwrap().is_isomorphic(&result_graph.unwrap()),
                         "Failure on positive evaluation test file {} about {}",
                         file,
                         comment
                     );
                 }
             }
-        },
-    );
+        });
 }
 
 #[test]
@@ -395,11 +209,14 @@ fn ntriples_w3c_testsuite() {
         NamedNode::from_str("http://www.w3.org/ns/rdftest#TestNTriplesNegativeSyntax").unwrap(),
     );
 
-    subjects_for_predicate_object(&manifest, &rdf::TYPE, &rdft_test_ntriples_positive_syntax)
+    manifest
+        .subjects_for_predicate_object(&rdf::TYPE, &rdft_test_ntriples_positive_syntax)
         .for_each(|test| {
-            let comment = object_for_subject_predicate(&manifest, test, &rdfs_comment).unwrap();
+            let comment = manifest
+                .object_for_subject_predicate(test, &rdfs_comment)
+                .unwrap();
             if let Some(Term::NamedNode(file)) =
-                object_for_subject_predicate(&manifest, test, &mf_action)
+                manifest.object_for_subject_predicate(test, &mf_action)
             {
                 if let Err(error) = client.load_ntriples(file.url().clone()) {
                     assert!(
@@ -410,11 +227,14 @@ fn ntriples_w3c_testsuite() {
                 }
             }
         });
-    subjects_for_predicate_object(&manifest, &rdf::TYPE, &rdft_test_ntriples_negative_syntax)
+    manifest
+        .subjects_for_predicate_object(&rdf::TYPE, &rdft_test_ntriples_negative_syntax)
         .for_each(|test| {
-            let comment = object_for_subject_predicate(&manifest, test, &rdfs_comment).unwrap();
+            let comment = manifest
+                .object_for_subject_predicate(test, &rdfs_comment)
+                .unwrap();
             if let Some(Term::NamedNode(file)) =
-                object_for_subject_predicate(&manifest, test, &mf_action)
+                manifest.object_for_subject_predicate(test, &mf_action)
             {
                 assert!(
                     client.load_ntriples(file.url().clone()).is_err(),