diff --git a/contracts/okp4-cognitarium/src/error.rs b/contracts/okp4-cognitarium/src/error.rs
index 6220b3aa..8012a946 100644
--- a/contracts/okp4-cognitarium/src/error.rs
+++ b/contracts/okp4-cognitarium/src/error.rs
@@ -1,4 +1,6 @@
 use cosmwasm_std::{StdError, Uint128};
+use rio_turtle::TurtleError;
+use rio_xml::RdfXmlError;
 use thiserror::Error;
 
 #[derive(Error, Debug, PartialEq)]
@@ -6,6 +8,9 @@ pub enum ContractError {
     #[error("{0}")]
     Std(#[from] StdError),
 
+    #[error("{0}")]
+    ParseRDF(#[from] RDFParseError),
+
     #[error("{0}")]
     Store(#[from] StoreError),
 
@@ -16,6 +21,18 @@ pub enum ContractError {
     NotImplemented,
 }
 
+impl From<RdfXmlError> for ContractError {
+    fn from(value: RdfXmlError) -> Self {
+        ContractError::ParseRDF(RDFParseError::from(value))
+    }
+}
+
+impl From<TurtleError> for ContractError {
+    fn from(value: TurtleError) -> Self {
+        ContractError::ParseRDF(RDFParseError::from(value))
+    }
+}
+
 #[derive(Error, Debug, PartialEq)]
 pub enum StoreError {
     #[error("Maximum triples number exceeded: {0}")]
@@ -39,3 +56,23 @@ pub enum StoreError {
     #[error("Maximum insert triple count exceeded: {0}")]
     MaxInsertDataTripleCount(Uint128),
 }
+
+#[derive(Error, Debug, PartialEq)]
+pub enum RDFParseError {
+    #[error("Error parsing XML RDF: {0}")]
+    XML(String),
+    #[error("Error parsing Turtle RDF: {0}")]
+    Turtle(String),
+}
+
+impl From<RdfXmlError> for RDFParseError {
+    fn from(value: RdfXmlError) -> Self {
+        RDFParseError::XML(value.to_string())
+    }
+}
+
+impl From<TurtleError> for RDFParseError {
+    fn from(value: TurtleError) -> Self {
+        RDFParseError::XML(value.to_string())
+    }
+}
diff --git a/contracts/okp4-cognitarium/src/state/triples.rs b/contracts/okp4-cognitarium/src/state/triples.rs
index 9e1d46e9..34851c3f 100644
--- a/contracts/okp4-cognitarium/src/state/triples.rs
+++ b/contracts/okp4-cognitarium/src/state/triples.rs
@@ -97,7 +97,7 @@ impl<'a> TryFrom<rio_api::model::Term<'a>> for Object {
             rio_api::model::Term::Literal(literal) => {
                 Literal::try_from(literal).map(|l| Object::Literal(l))
             }
-            _ => Err(StdError::generic_err("Not implemented")),
+            _ => Err(StdError::generic_err("RDF star syntax unsupported")),
         }
     }
 }