diff --git a/shex_validation/src/validator_runner.rs b/shex_validation/src/validator_runner.rs
index 1f9a1434..719d1be0 100644
--- a/shex_validation/src/validator_runner.rs
+++ b/shex_validation/src/validator_runner.rs
@@ -377,7 +377,7 @@ impl ValidatorRunner {
         S: SRDF,
     {
         let node = self.get_rdf_node(node, rdf);
-        let list = preds.iter().map(|pred| S::iri_s2iri(pred)).collect();
+        let list: Vec<_> = preds.iter().map(|pred| S::iri_s2iri(pred)).collect();
         if let Some(subject) = S::term_as_subject(&node) {
             let (outgoing_arcs, remainder) = rdf
                 .outgoing_arcs_from_list(&subject, &list)
diff --git a/sparql_service/src/srdf_data/rdf_data.rs b/sparql_service/src/srdf_data/rdf_data.rs
index 873ce262..b11b23df 100644
--- a/sparql_service/src/srdf_data/rdf_data.rs
+++ b/sparql_service/src/srdf_data/rdf_data.rs
@@ -93,6 +93,12 @@ impl RdfData {
     }
 }
 
+impl Default for RdfData {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl SRDFBasic for RdfData {
     type IRI = OxNamedNode;
     type BNode = OxBlankNode;
@@ -366,11 +372,11 @@ fn cnv_query_solution(qs: QuerySolution) -> QuerySolution2<RdfData> {
     let mut variables = Vec::new();
     let mut values = Vec::new();
     for v in qs.variables() {
-        let varname = VarName2::from_str(v.as_str());
+        let varname = VarName2::new(v.as_str());
         variables.push(varname);
     }
     for t in qs.values() {
-        let term = t.as_ref().map(|t| t.clone());
+        let term = t.clone();
         values.push(term)
     }
     QuerySolution2::new(Rc::new(variables), values)
@@ -447,7 +453,7 @@ impl SRDF for RdfData {
     fn outgoing_arcs_from_list(
         &self,
         subject: &Self::Subject,
-        preds: &Vec<Self::IRI>,
+        preds: &[Self::IRI],
     ) -> Result<(HashMap<Self::IRI, HashSet<Self::Term>>, Vec<Self::IRI>), Self::Err> {
         let mut result = (HashMap::new(), Vec::new());
         if let Some(graph) = &self.graph {
diff --git a/srdf/src/query_srdf2.rs b/srdf/src/query_srdf2.rs
index 80ef9589..99259f6e 100644
--- a/srdf/src/query_srdf2.rs
+++ b/srdf/src/query_srdf2.rs
@@ -23,7 +23,7 @@ impl Display for VarName2 {
 }
 
 impl VarName2 {
-    pub fn from_str(str: &str) -> VarName2 {
+    pub fn new(str: &str) -> VarName2 {
         VarName2 {
             str: str.to_string(),
         }
@@ -88,10 +88,7 @@ impl<S: SRDFBasic> QuerySolution2<S> {
         let cnv_values: Vec<Option<T::Term>> = self
             .values
             .iter()
-            .map(|s| match s {
-                None => None,
-                Some(s) => Some(cnv_term(s)),
-            })
+            .map(|s| s.as_ref().map(&cnv_term))
             .collect();
         QuerySolution2 {
             variables: self.variables.clone(),
diff --git a/srdf/src/srdf.rs b/srdf/src/srdf.rs
index 5af44f29..9dd6f1ad 100644
--- a/srdf/src/srdf.rs
+++ b/srdf/src/srdf.rs
@@ -76,6 +76,6 @@ pub trait SRDF: SRDFBasic {
     fn outgoing_arcs_from_list(
         &self,
         subject: &Self::Subject,
-        preds: &Vec<Self::IRI>,
+        preds: &[Self::IRI],
     ) -> Result<OutgoingArcs<Self::IRI, Self::Term>, Self::Err>;
 }
diff --git a/srdf/src/srdf_graph/srdfgraph.rs b/srdf/src/srdf_graph/srdfgraph.rs
index 5ce0aabf..6a91e72f 100644
--- a/srdf/src/srdf_graph/srdfgraph.rs
+++ b/srdf/src/srdf_graph/srdfgraph.rs
@@ -562,7 +562,7 @@ impl SRDF for SRDFGraph {
     fn outgoing_arcs_from_list(
         &self,
         subject: &Self::Subject,
-        preds: &Vec<Self::IRI>,
+        preds: &[Self::IRI],
     ) -> Result<(HashMap<Self::IRI, HashSet<Self::Term>>, Vec<Self::IRI>), Self::Err> {
         let mut results: HashMap<Self::IRI, HashSet<Self::Term>> = HashMap::new();
         let mut remainder = Vec::new();
diff --git a/srdf/src/srdf_sparql/srdfsparql.rs b/srdf/src/srdf_sparql/srdfsparql.rs
index b7738f02..3ba9f5e1 100644
--- a/srdf/src/srdf_sparql/srdfsparql.rs
+++ b/srdf/src/srdf_sparql/srdfsparql.rs
@@ -381,7 +381,7 @@ impl SRDF for SRDFSparql {
     fn outgoing_arcs_from_list(
         &self,
         subject: &Self::Subject,
-        preds: &Vec<Self::IRI>,
+        preds: &[Self::IRI],
     ) -> std::prelude::v1::Result<
         (HashMap<Self::IRI, HashSet<Self::Term>>, Vec<Self::IRI>),
         Self::Err,
@@ -431,7 +431,7 @@ impl QuerySRDF2 for SRDFSparql {
     fn query_select(&self, query: &str) -> Result<QuerySolutions<Self>> {
         let solutions = make_sparql_query(query, &self.client, &self.endpoint_iri)?;
         let qs: Vec<QuerySolution2<SRDFSparql>> =
-            solutions.iter().map(|s| cnv_query_solution(s)).collect();
+            solutions.iter().map(cnv_query_solution).collect();
         Ok(QuerySolutions::new(qs))
     }
 
@@ -452,14 +452,11 @@ fn cnv_query_solution(qs: &OxQuerySolution) -> QuerySolution2<SRDFSparql> {
     let mut variables = Vec::new();
     let mut values = Vec::new();
     for v in qs.variables() {
-        let varname = VarName2::from_str(v.as_str());
+        let varname = VarName2::new(v.as_str());
         variables.push(varname);
     }
     for t in qs.values() {
-        let term = match &t {
-            None => None,
-            Some(t) => Some(t.clone()),
-        };
+        let term = t.clone();
         values.push(term)
     }
     QuerySolution2::new(Rc::new(variables), values)
@@ -579,7 +576,7 @@ type OutputNodes = HashMap<OxNamedNode, HashSet<OxTerm>>;
 
 fn outgoing_neighs_from_list(
     subject: &OxSubject,
-    preds: &Vec<OxNamedNode>,
+    preds: &[OxNamedNode],
     client: &Client,
     endpoint_iri: &IriS,
 ) -> Result<(OutputNodes, Vec<OxNamedNode>)> {