chore(cognitarium): add atoms definition to help with rdf serde

contracts/okp4-cognitarium/src/rdf/atom.rs

@@ -0,0 +1,38 @@
+#[derive(Eq, PartialEq, Debug, Clone, Hash)]
+pub enum Value {
+    NamedNode(String),
+    BlankNode(String),
+    LiteralSimple(String),
+    LiteralLang(String, String),
+    LiteralDatatype(String, String),
+}
+
+use std::fmt;
+impl fmt::Display for Value {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Value::NamedNode(s) => write!(f, "{}", s),
+            Value::BlankNode(s) => write!(f, "{}", s),
+            Value::LiteralSimple(s) => write!(f, "{}", s),
+            Value::LiteralLang(s, l) => write!(f, "{}@{}", s, l),
+            Value::LiteralDatatype(s, d) => write!(f, "{}^^{}", s, d),
+        }
+    }
+}
+
+#[derive(Eq, PartialEq, Debug, Clone, Hash)]
+pub struct Atom {
+    pub subject: String,
+    pub property: String,
+    pub value: Value,
+}
+
+impl std::fmt::Display for Atom {
+    fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
+        fmt.write_str(&format!(
+            "<{}> <{}> '{}'",
+            self.subject, self.property, self.value
+        ))?;
+        Ok(())
+    }
+}

contracts/okp4-cognitarium/src/rdf/mod.rs

@@ -1,5 +1,7 @@
 mod serde;
 mod uri;
+mod atom;
 
 pub use self::serde::*;
 pub use self::uri::*;
+pub use self::atom::*;

contracts/okp4-cognitarium/src/rdf/serde.rs

@@ -122,23 +122,3 @@ impl<W: std::io::Write> TripleWriter<W> {
         }
     }
 }
-
-// Convenient type which simplifies the management of the lifetime of the IRI
-#[derive(Eq, PartialEq, Ord, PartialOrd, Debug, Clone, Hash)]
-pub struct OwnedNamedNode {
-    pub iri: String,
-}
-
-impl From<NamedNode<'_>> for OwnedNamedNode {
-    fn from(n: NamedNode<'_>) -> Self {
-        Self {
-            iri: n.iri.to_owned(),
-        }
-    }
-}
-
-impl<'a> From<&'a OwnedNamedNode> for NamedNode<'a> {
-    fn from(n: &'a OwnedNamedNode) -> Self {
-        Self { iri: &n.iri }
-    }
-}