diff --git a/trellis-api/src/main/java/org/trellisldp/api/ImmutableDataService.java b/trellis-api/src/main/java/org/trellisldp/api/ImmutableDataService.java
index 0aff47870..3699c72ef 100644
--- a/trellis-api/src/main/java/org/trellisldp/api/ImmutableDataService.java
+++ b/trellis-api/src/main/java/org/trellisldp/api/ImmutableDataService.java
@@ -16,16 +16,17 @@
 
 import java.util.concurrent.Future;
 
+import org.apache.commons.rdf.api.IRI;
+
 /**
  * A service that persists resources by appending to their records. Nothing that
  * is recorded by {@link #add} will be deleted by using {@code add} again.
  * 
  * @author ajs6f
  *
- * @param <T> the type of identifier for resources that can be persisted by this service
- * @param <U> the type of resource that can be persisted by this service
+ * @param <T> the type of resource that can be persisted by this service
  */
-public interface ImmutableDataService<T, U> extends RetrievalService<T, U> {
+public interface ImmutableDataService<T> extends RetrievalService<T> {
 
     /**
      * @param identifier the identifier under which to persist a resource
@@ -33,5 +34,5 @@ public interface ImmutableDataService<T, U> extends RetrievalService<T, U> {
      * @param resource a resource to persist
      * @return whether the resource was successfully persisted
      */
-    Future<Boolean> add(T identifier, Session session, U resource);
+    Future<Boolean> add(IRI identifier, Session session, T resource);
 }
diff --git a/trellis-api/src/main/java/org/trellisldp/api/JoiningResourceService.java b/trellis-api/src/main/java/org/trellisldp/api/JoiningResourceService.java
index bbc0633cb..449ea6478 100644
--- a/trellis-api/src/main/java/org/trellisldp/api/JoiningResourceService.java
+++ b/trellis-api/src/main/java/org/trellisldp/api/JoiningResourceService.java
@@ -35,16 +35,16 @@
  */
 public abstract class JoiningResourceService implements ResourceService {
 
-    private final ImmutableDataService<IRI, Resource> immutableData;
+    private final ImmutableDataService<Resource> immutableData;
 
-    private final MutableDataService<IRI, Resource> mutableData;
+    private final MutableDataService<Resource> mutableData;
 
     /**
      * @param mutableData service in which to persist mutable data
      * @param immutableData service in which to persist immutable data
      */
-    public JoiningResourceService(final MutableDataService<IRI, Resource> mutableData,
-                    final ImmutableDataService<IRI, Resource> immutableData) {
+    public JoiningResourceService(final MutableDataService<Resource> mutableData,
+                    final ImmutableDataService<Resource> immutableData) {
         this.immutableData = immutableData;
         this.mutableData = mutableData;
     }
diff --git a/trellis-api/src/main/java/org/trellisldp/api/MutableDataService.java b/trellis-api/src/main/java/org/trellisldp/api/MutableDataService.java
index 6c1fd5481..36cc685cf 100644
--- a/trellis-api/src/main/java/org/trellisldp/api/MutableDataService.java
+++ b/trellis-api/src/main/java/org/trellisldp/api/MutableDataService.java
@@ -16,14 +16,15 @@
 
 import java.util.concurrent.Future;
 
+import org.apache.commons.rdf.api.IRI;
+
 /**
  * A service that persists resources by <i>replacing</i> their records.
  *
  * @author ajs6f
- * @param <T> the type of identifier used by this service
  * @param <U> the type of resource that can be persisted by this service
  */
-public interface MutableDataService<T, U> extends RetrievalService<T, U> {
+public interface MutableDataService<U> extends RetrievalService<U> {
 
     /**
      * @param identifier the identifier for the resource to persist
@@ -31,7 +32,7 @@ public interface MutableDataService<T, U> extends RetrievalService<T, U> {
      * @param resource a resource to persist
      * @return whether the resource was successfully persisted
      */
-    Future<Boolean> create(T identifier, Session session, U resource);
+    Future<Boolean> create(IRI identifier, Session session, U resource);
 
     /**
      * @param identifier the identifier for the resource to persist
@@ -39,7 +40,7 @@ public interface MutableDataService<T, U> extends RetrievalService<T, U> {
      * @param resource a resource to persist
      * @return whether the resource was successfully persisted
      */
-    Future<Boolean> replace(T identifier, Session session, U resource);
+    Future<Boolean> replace(IRI identifier, Session session, U resource);
 
     /**
      * @param identifier the identifier for the resource to delete
@@ -47,6 +48,6 @@ public interface MutableDataService<T, U> extends RetrievalService<T, U> {
      * @param resource a resource to delete
      * @return whether the resource was successfully deleted
      */
-    Future<Boolean> delete(T identifier, Session session, U resource);
+    Future<Boolean> delete(IRI identifier, Session session, U resource);
 
 }
diff --git a/trellis-api/src/main/java/org/trellisldp/api/ResourceService.java b/trellis-api/src/main/java/org/trellisldp/api/ResourceService.java
index 886c4a824..07454c7ac 100644
--- a/trellis-api/src/main/java/org/trellisldp/api/ResourceService.java
+++ b/trellis-api/src/main/java/org/trellisldp/api/ResourceService.java
@@ -39,8 +39,7 @@
  *
  * @author acoburn
  */
-public interface ResourceService extends MutableDataService<IRI, Resource>,
-       ImmutableDataService<IRI, Resource> {
+public interface ResourceService extends MutableDataService<Resource>, ImmutableDataService<Resource> {
 
     @Override
     default Future<Boolean> add(IRI identifier, Session session, Resource resource) {
diff --git a/trellis-api/src/main/java/org/trellisldp/api/RetrievalService.java b/trellis-api/src/main/java/org/trellisldp/api/RetrievalService.java
index a7601a6d3..397c4f92c 100644
--- a/trellis-api/src/main/java/org/trellisldp/api/RetrievalService.java
+++ b/trellis-api/src/main/java/org/trellisldp/api/RetrievalService.java
@@ -17,15 +17,16 @@
 import java.time.Instant;
 import java.util.Optional;
 
+import org.apache.commons.rdf.api.IRI;
+
 /**
  * A service that can retrieve resources of some type, featuring optional
  * retrieval by time.
  * 
  * @author ajs6f
- * @param <T> the type of identifier used by this service
- * @param <U> the type of resource available from this service
+ * @param <T> the type of resource available from this service
  */
-public interface RetrievalService<T, U> {
+public interface RetrievalService<T> {
 
     /**
      * Get a resource by the given identifier.
@@ -33,7 +34,7 @@ public interface RetrievalService<T, U> {
      * @param identifier the resource identifier
      * @return the resource
      */
-    Optional<? extends U> get(T identifier);
+    Optional<? extends T> get(IRI identifier);
 
     /**
      * Get a resource by the given identifier and time.
@@ -42,7 +43,7 @@ public interface RetrievalService<T, U> {
      * @param time the time
      * @return the resource
      */
-    default Optional<? extends U> get(T identifier, Instant time) {
+    default Optional<? extends T> get(IRI identifier, Instant time) {
         return get(identifier);
     }
 }
diff --git a/trellis-api/src/test/java/org/trellisldp/api/JoiningResourceServiceTest.java b/trellis-api/src/test/java/org/trellisldp/api/JoiningResourceServiceTest.java
index 59d89d3f1..90c14be86 100644
--- a/trellis-api/src/test/java/org/trellisldp/api/JoiningResourceServiceTest.java
+++ b/trellis-api/src/test/java/org/trellisldp/api/JoiningResourceServiceTest.java
@@ -66,7 +66,7 @@ private static Quad createQuad(final BlankNodeOrIRI g, final BlankNodeOrIRI s, f
 
     private static IRI badId = createIRI("http://bad.com");
 
-    private static class TestableRetrievalService implements RetrievalService<IRI, Resource> {
+    private static class TestableRetrievalService implements RetrievalService<Resource> {
 
         protected final Map<IRI, Resource> resources = synchronizedMap(new HashMap<>());
 
@@ -82,7 +82,7 @@ protected CompletableFuture<Boolean> isntBadId(final IRI identifier) {
     }
 
     private static class TestableImmutableService extends TestableRetrievalService
-                    implements ImmutableDataService<IRI, Resource> {
+                    implements ImmutableDataService<Resource> {
 
         @Override
         public Future<Boolean> add(final IRI identifier, final Session session, final Resource newRes) {
@@ -91,10 +91,10 @@ public Future<Boolean> add(final IRI identifier, final Session session, final Re
         }
     }
 
-    private final ImmutableDataService<IRI, Resource> testImmutableService = new TestableImmutableService();
+    private final ImmutableDataService<Resource> testImmutableService = new TestableImmutableService();
 
     private static class TestableMutableDataService extends TestableRetrievalService
-                    implements MutableDataService<IRI, Resource> {
+                    implements MutableDataService<Resource> {
 
         @Override
         public Future<Boolean> create(final IRI identifier, final Session session, final Resource resource) {
@@ -115,12 +115,12 @@ public Future<Boolean> delete(final IRI identifier, final Session session, final
         }
     };
 
-    private final MutableDataService<IRI, Resource> testMutableService = new TestableMutableDataService();
+    private final MutableDataService<Resource> testMutableService = new TestableMutableDataService();
 
     private static class TestableJoiningResourceService extends JoiningResourceService {
 
-        public TestableJoiningResourceService(final ImmutableDataService<IRI, Resource> immutableData,
-                        final MutableDataService<IRI, Resource> mutableData) {
+        public TestableJoiningResourceService(final ImmutableDataService<Resource> immutableData,
+                        final MutableDataService<Resource> mutableData) {
             super(mutableData, immutableData);
         }
 
diff --git a/trellis-api/src/test/java/org/trellisldp/api/ResourceServiceTest.java b/trellis-api/src/test/java/org/trellisldp/api/ResourceServiceTest.java
index 741838173..596d0ef44 100644
--- a/trellis-api/src/test/java/org/trellisldp/api/ResourceServiceTest.java
+++ b/trellis-api/src/test/java/org/trellisldp/api/ResourceServiceTest.java
@@ -66,9 +66,9 @@ public class ResourceServiceTest {
     private static Resource mockResource;
 
     @Mock
-    private RetrievalService<IRI, Resource> mockRetrievalService;
+    private RetrievalService<Resource> mockRetrievalService;
 
-    private static class MyRetrievalService implements RetrievalService<IRI, Resource> {
+    private static class MyRetrievalService implements RetrievalService<Resource> {
         @Override
         public Optional<Resource> get(final IRI id) {
             return of(mockResource);
@@ -94,7 +94,7 @@ public void setUp() {
 
     @Test
     public void testRetrievalService2() {
-        final RetrievalService<IRI, Resource> svc = new MyRetrievalService();
+        final RetrievalService<Resource> svc = new MyRetrievalService();
         final Optional<? extends Resource> res = svc.get(existing);
         final Optional<? extends Resource> res2 = svc.get(existing, now());
         assertTrue(res.isPresent());