added some docs

lib/src/repository.rs

@@ -85,7 +85,7 @@ pub trait RepositoryConnection: Clone {
     /// ```
     fn prepare_query<'a>(&'a self, query: &str, base_iri: Option<&'a str>) -> Result<Self::PreparedQuery>;
 
-
+    /// This is similar to `prepare_query`, but useful if a SPARQL query has already been parsed, which is the case when building `ServiceHandler`s for federated queries with `SERVICE` clauses. For examples, look in the tests.
     fn prepare_query_from_pattern<'a>(
         &'a self,
         graph_pattern: &'a GraphPattern,

lib/src/sparql/eval.rs

@@ -1662,6 +1662,7 @@ impl<'a, S: StoreConnection + 'a> SimpleEvaluator<S> {
         )
     }
 
+    // this is used to encode results froma BindingIterator into an EncodedTuplesIterator. This happens when SERVICE clauses are evaluated
     fn encode_bindings<'b>(
         &'b self,
         variables: &'b [Variable],

lib/src/sparql/mod.rs

@@ -117,6 +117,7 @@ impl<'a, S: StoreConnection + 'a> SimplePreparedQuery<S> {
         }))
     }
 
+    /// Builds SimplePreparedQuery from an existing `GraphPattern`. This is used to support federated queries via `SERVICE` clauses
     pub(crate) fn new_from_pattern(
         connection: S,
         pattern: &GraphPattern,