diff --git a/src/model/data.rs b/src/model/data.rs
index 887ffc70..143471f1 100644
--- a/src/model/data.rs
+++ b/src/model/data.rs
@@ -2,8 +2,10 @@
 ///! Inspired by [RDFjs](http://rdf.js.org/)
 use std::fmt;
 use std::option::Option;
+use std::str::FromStr;
 use std::sync::Arc;
 use std::sync::Mutex;
+use url::ParseError;
 use url::Url;
 
 /// A RDF [IRI](https://www.w3.org/TR/rdf11-concepts/#dfn-iri)
@@ -28,6 +30,16 @@ impl fmt::Display for NamedNode {
     }
 }
 
+impl FromStr for NamedNode {
+    type Err = ParseError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        Ok(NamedNode {
+            iri: Arc::new(Url::parse(s)?),
+        })
+    }
+}
+
 /// A RDF [blank node](https://www.w3.org/TR/rdf11-concepts/#dfn-blank-node)
 #[derive(Eq, PartialEq, Debug, Clone, Hash)]
 pub struct BlankNode {
@@ -55,12 +67,12 @@ pub enum Literal {
 }
 
 lazy_static! {
-    static ref XSD_STRING: NamedNode = NamedNode {
-        iri: Arc::new(Url::parse("http://www.w3.org/2001/XMLSchema#string").unwrap())
-    };
-    static ref RDF_LANG_STRING: NamedNode = NamedNode {
-        iri: Arc::new(Url::parse("http://www.w3.org/1999/02/22-rdf-syntax-ns#langString").unwrap())
-    };
+    static ref XSD_BOOLEAN: NamedNode =
+        NamedNode::from_str("http://www.w3.org/2001/XMLSchema#boolean").unwrap();
+    static ref XSD_STRING: NamedNode =
+        NamedNode::from_str("http://www.w3.org/2001/XMLSchema#string").unwrap();
+    static ref RDF_LANG_STRING: NamedNode =
+        NamedNode::from_str("http://www.w3.org/1999/02/22-rdf-syntax-ns#langString").unwrap();
 }
 
 impl Literal {
@@ -112,6 +124,35 @@ impl fmt::Display for Literal {
     }
 }
 
+impl<'a> From<&'a str> for Literal {
+    fn from(value: &'a str) -> Self {
+        Literal::SimpleLiteral(value.into())
+    }
+}
+
+impl From<String> for Literal {
+    fn from(value: String) -> Self {
+        Literal::SimpleLiteral(value)
+    }
+}
+
+impl From<bool> for Literal {
+    fn from(value: bool) -> Self {
+        Literal::TypedLiteral {
+            value: value.to_string(),
+            datatype: XSD_BOOLEAN.clone(),
+        }
+    }
+}
+
+impl FromStr for Literal {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        Ok(s.clone().into())
+    }
+}
+
 /// The 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).
 #[derive(Eq, PartialEq, Debug, Clone, Hash)]
 pub enum NamedOrBlankNode {
diff --git a/src/rio/ntriples/ntriples_grammar.rustpeg b/src/rio/ntriples/ntriples_grammar.rustpeg
index ade1796a..1868e97c 100644
--- a/src/rio/ntriples/ntriples_grammar.rustpeg
+++ b/src/rio/ntriples/ntriples_grammar.rustpeg
@@ -2,7 +2,7 @@
 
 use std::iter::FromIterator;
 use std::char;
-use url::Url;
+use std::str::FromStr;
 use model::data::*;
 
 #![arguments(data_factory: &DataFactory)]
@@ -15,25 +15,25 @@ triple -> Option<Triple> =
 
 //[3]
 subject -> NamedOrBlankNode =
-    i: IRIREF { data_factory.named_node(i).into() } /
-    b: BLANK_NODE_LABEL { data_factory.blank_node(b).into() }
+    i: IRIREF { i.into() } /
+    b: BLANK_NODE_LABEL { b.into() }
 
 //[4]
 predicate -> NamedNode = i:IRIREF {
-    data_factory.named_node(i)
+    i
 }
 
 //[5]
 object -> Term =
-    i: IRIREF { data_factory.named_node(i).into() } /
-    b: BLANK_NODE_LABEL { data_factory.blank_node(b).into() } /
+    i: IRIREF { i.into() } /
+    b: BLANK_NODE_LABEL { b.into() } /
     l: literal { l.into() }
 
 //[6]
 literal -> Literal =
-    v: STRING_LITERAL_QUOTE _ "^^" _ t:IRIREF { data_factory.typed_literal(v, data_factory.named_node(t)) } /
+    v: STRING_LITERAL_QUOTE _ "^^" _ t:IRIREF { data_factory.typed_literal(v, t) } /
     v: STRING_LITERAL_QUOTE _ l:LANGTAG { data_factory.language_tagged_literal(v, l) } /
-    v: STRING_LITERAL_QUOTE { data_factory.simple_literal(v) }
+    v: STRING_LITERAL_QUOTE { v.into() }
 
 
 //[144s]
@@ -45,10 +45,10 @@ LANGTAG -> &'input str = "@" l:$([a-zA-Z]+ ("-" [a-zA-Z0-9]+)*) {
 EOL = [\r\n]+
 
 //[8]
-IRIREF -> Url = "<" _ i:((_IRIREF_simple_char / UCHAR)*) _ ">" {?
+IRIREF -> NamedNode = "<" _ i:((_IRIREF_simple_char / UCHAR)*) _ ">" {?
     let s = String::from_iter(i.into_iter());
-    match Url::parse(&s) {
-        Ok(url) => Ok(url),
+    match NamedNode::from_str(&s) {
+        Ok(named_node) => Ok(named_node),
         Err(error) => Err("IRI parsing failed")
     }
 }
@@ -61,8 +61,8 @@ STRING_LITERAL_QUOTE -> String = "\"" l:((STRING_LITERAL_QUOTE_simple_char / ECH
 STRING_LITERAL_QUOTE_simple_char -> char = c: $([^\u{0022}\u{005c}\u{000a}\u{000d}]) { c.chars().next().unwrap() }
 
 //[141s]
-BLANK_NODE_LABEL -> &'input str = "_:" b:$(([0-9] / PN_CHARS_U) PN_CHARS* ("."+ PN_CHARS+)*) {
-    b
+BLANK_NODE_LABEL -> BlankNode = "_:" b:$(([0-9] / PN_CHARS_U) PN_CHARS* ("."+ PN_CHARS+)*) {
+    data_factory.blank_node(b)
 }
 
 //[10]
diff --git a/src/rio/turtle/turtle_grammar.rustpeg b/src/rio/turtle/turtle_grammar.rustpeg
index 3273e3ac..6a327939 100644
--- a/src/rio/turtle/turtle_grammar.rustpeg
+++ b/src/rio/turtle/turtle_grammar.rustpeg
@@ -3,6 +3,7 @@
 use std::char;
 use url::Url;
 use model::data::*;
+use std::str::FromStr;
 use std::iter;
 use rio::turtle::ParserState;
 
@@ -70,7 +71,7 @@ objectList -> () = object _ ("," _ object _)*
 
 //[9]
 verb -> NamedNode = predicate /
-    "a" { data_factory.named_node(Url::parse("http://www.w3.org/1999/02/22-rdf-syntax-ns#type").unwrap()) }
+    "a" { NamedNode::from_str("http://www.w3.org/1999/02/22-rdf-syntax-ns#type").unwrap() }
 
 // [10]
 subject -> NamedOrBlankNode =
@@ -115,9 +116,9 @@ blankNodePropertyList_open -> () = "[" {
 
 //[15]
 collection -> NamedOrBlankNode = '(' _ o:(collection_value*) ')' {
-    let first = data_factory.named_node(Url::parse("http://www.w3.org/1999/02/22-rdf-syntax-ns#first").unwrap());
-    let rest = data_factory.named_node(Url::parse("http://www.w3.org/1999/02/22-rdf-syntax-ns#rest").unwrap());
-    let mut current_list_node = NamedOrBlankNode::from(data_factory.named_node(Url::parse("http://www.w3.org/1999/02/22-rdf-syntax-ns#nil").unwrap()));
+    let first = NamedNode::from_str("http://www.w3.org/1999/02/22-rdf-syntax-ns#first").unwrap();
+    let rest = NamedNode::from_str("http://www.w3.org/1999/02/22-rdf-syntax-ns#rest").unwrap();
+    let mut current_list_node = NamedOrBlankNode::from(NamedNode::from_str("http://www.w3.org/1999/02/22-rdf-syntax-ns#nil").unwrap());
     for obj in o.into_iter().rev() {
         let new_blank_node = NamedOrBlankNode::from(data_factory.new_blank_node());
         buffer.push(data_factory.triple(new_blank_node.clone(), first.clone(), obj));
@@ -130,20 +131,20 @@ collection_value -> Term = o:object_value _ { o }
 
 //[16]
 NumericLiteral -> Literal =
-    d:$(DOUBLE) { data_factory.typed_literal(d, data_factory.named_node(Url::parse("http://www.w3.org/2001/XMLSchema#double").unwrap())) } /
-    d:$(DECIMAL) { data_factory.typed_literal(d, data_factory.named_node(Url::parse("http://www.w3.org/2001/XMLSchema#decimal").unwrap())) } /
-    i:$(INTEGER) { data_factory.typed_literal(i, data_factory.named_node(Url::parse("http://www.w3.org/2001/XMLSchema#integer").unwrap())) }
+    d:$(DOUBLE) { data_factory.typed_literal(d, NamedNode::from_str("http://www.w3.org/2001/XMLSchema#double").unwrap()) } /
+    d:$(DECIMAL) { data_factory.typed_literal(d, NamedNode::from_str("http://www.w3.org/2001/XMLSchema#decimal").unwrap()) } /
+    i:$(INTEGER) { data_factory.typed_literal(i, NamedNode::from_str("http://www.w3.org/2001/XMLSchema#integer").unwrap()) }
 
 //[128s]
 RDFLiteral -> Literal =
     v:String _ "^^" _ t:iri { data_factory.typed_literal(v, t) } /
     v:String _ l:LANGTAG { data_factory.language_tagged_literal(v, l) } /
-    v:String { data_factory.simple_literal(v) }
+    v:String { v.into() }
 
 //[133s]
 BooleanLiteral -> Literal =
-    "true" { data_factory.typed_literal("true", data_factory.named_node(Url::parse("http://www.w3.org/2001/XMLSchema#boolean").unwrap())) } /
-    "false" { data_factory.typed_literal("false", data_factory.named_node(Url::parse("http://www.w3.org/2001/XMLSchema#boolean").unwrap())) }
+    "true" { true.into() } /
+    "false" { false.into() }
 
 //[17]
 String -> String = STRING_LITERAL_LONG_SINGLE_QUOTE / STRING_LITERAL_LONG_QUOTE / STRING_LITERAL_QUOTE / STRING_LITERAL_SINGLE_QUOTE