diff --git a/prefix_map/src/prefix_map.rs b/prefix_map/src/prefix_map.rs
index 81c5c2e3..9c6b383c 100644
--- a/prefix_map/src/prefix_map.rs
+++ b/prefix_map/src/prefix_map.rs
@@ -100,5 +100,15 @@ mod tests {
         assert_eq!(pm.to_string(), 
           "ex <http://example.org/>\nrdf <http://www.w3.org/1999/02/22-rdf-syntax-ns#>\n");
     }
+
+    #[test]
+    fn prefix_map_resolve() {
+        let mut pm = PrefixMap::new();
+        let ex_iri = IriS::from_str("http://example.org/").unwrap(); 
+        pm.insert("ex", &ex_iri);
+        assert_eq!(pm.resolve(&"ex:pepe").unwrap(), 
+          Some(IriS::from_str("http://example.org/pepe").unwrap()));
+    }
+
 }
 
diff --git a/shex_ast/src/schema.rs b/shex_ast/src/schema.rs
index 2390094f..a0fcfd1d 100644
--- a/shex_ast/src/schema.rs
+++ b/shex_ast/src/schema.rs
@@ -1,15 +1,27 @@
+use iri_s::IriError;
 use prefix_map::PrefixMap;
 use srdf::iri::IriS;
 
 #[derive(Debug)]
 pub struct Schema<'a> {
-  pub id: Option<Box<IriS>>,
-  pub base: Option<Box<IriS>>,
-  pub prefixes: Option<PrefixMap<'a>>
+  pub(crate) id: Option<IriS>,
+  pub(crate) base: Option<IriS>,
+  pub(crate) prefixes: Option<PrefixMap<'a>>
 }
 
 
 impl <'a> Schema<'a> {
-    pub fn base(&self) -> &Option<Box<IriS>> { &self.base }
+
+  pub fn id(&self) -> Option<IriS> { self.id.clone() }
+
+  pub fn base(&self) -> Option<IriS> { self.base.clone() }
+
+  pub fn resolve(&self, alias: &str) -> Result<Option<IriS>, IriError> { 
+    match &self.prefixes {
+      Some(pm) => pm.resolve(alias),
+      None => Ok(None)
+    }
+  }
+
 }
 
diff --git a/shex_ast/src/schema_builder.rs b/shex_ast/src/schema_builder.rs
index 58c2c918..36723bbe 100644
--- a/shex_ast/src/schema_builder.rs
+++ b/shex_ast/src/schema_builder.rs
@@ -25,8 +25,8 @@ impl Error for ErrorBuildingSchema {}
 // type Result<T> = Result<T,ErrorBuildingSchema>
 
 struct SchemaParts<'a> {
-    id: Option<Box<IriS>>,
-    base: Option<Box<IriS>>,
+    id: Option<IriS>,
+    base: Option<IriS>,
     prefixes: PrefixMap<'a>,
     shapes_counter: u32
 }
@@ -45,7 +45,7 @@ impl <'a> SchemaBuilder<'a> {
 
     pub fn set_base(self, base: IriS) -> SchemaBuilder<'a> {
         self.and_then(move |mut schema_parts| {
-            schema_parts.base = Some(Box::new(base));
+            schema_parts.base = Some(base);
             Ok(schema_parts)
         })
     }
@@ -103,14 +103,29 @@ mod tests {
      Ok(sb.set_base(iri))
   }
 
+  fn update_prefix_map<'a>(sb: SchemaBuilder<'a>, alias: &'a str, iri: &'a IriS) -> Result<SchemaBuilder<'a>, ErrorBuildingSchema> {
+    Ok(sb.add_prefix(alias,&iri))
+ }
 
  #[test]
- fn test_update() {
+ fn test_update_base() {
     let sb = SchemaBuilder::new();
     let iri = IriS::from_str("http://example.org/").unwrap();
     let schema = update_base(sb, iri).unwrap().build().unwrap();
-    assert_eq!(schema.base(), &Some(Box::new(IriS::from_str("http://example.org/").unwrap())));
+    assert_eq!(schema.base(), Some(IriS::from_str("http://example.org/").unwrap()));
  }
 
+ #[test]
+ fn test_update_prefix_map() {
+    let sb = SchemaBuilder::new();
+    let iri = IriS::from_str("http://example.org/").unwrap();
+    let schema = update_prefix_map(sb, &"ss", &iri).unwrap().build().unwrap();
+    assert_eq!(
+        schema.resolve(&"ss:foo").unwrap(), 
+        Some(IriS::from_str("http://example.org/foo").unwrap())
+    );
+ }
+
+
 }