diff --git a/jena-arq/src/main/java/org/apache/jena/rdfs/assembler/VocabRDFS.java b/jena-arq/src/main/java/org/apache/jena/rdfs/assembler/VocabRDFS.java
index 2745a9b..5ba42bd 100644
--- a/jena-arq/src/main/java/org/apache/jena/rdfs/assembler/VocabRDFS.java
+++ b/jena-arq/src/main/java/org/apache/jena/rdfs/assembler/VocabRDFS.java
@@ -20,12 +20,9 @@
 
 import org.apache.jena.assembler.Assembler;
 import org.apache.jena.assembler.JA;
-import org.apache.jena.irix.IRIException;
-import org.apache.jena.irix.IRIx;
 import org.apache.jena.rdf.model.Property;
 import org.apache.jena.rdf.model.Resource;
 import org.apache.jena.rdf.model.ResourceFactory;
-import org.apache.jena.shared.JenaException;
 import org.apache.jena.sparql.core.assembler.AssemblerUtils;
 import org.apache.jena.sparql.core.assembler.DatasetAssemblerVocab;
 import org.apache.jena.sys.JenaSystem;
@@ -64,13 +61,6 @@
 
     private static String iri(String localname) {
         String uri = NS + localname;
-        try {
-            IRIx iri = IRIx.create(uri);
-            if ( ! iri.isReference() )
-                throw new JenaException("Bad IRI (relative): "+uri);
-            return uri;
-        } catch (IRIException ex) {
-            throw new JenaException("Bad IRI: "+uri);
-        }
+        return uri;
     }
 }
diff --git a/jena-arq/src/main/java/org/apache/jena/riot/RDFParser.java b/jena-arq/src/main/java/org/apache/jena/riot/RDFParser.java
index 4e75027..eaa926b 100644
--- a/jena-arq/src/main/java/org/apache/jena/riot/RDFParser.java
+++ b/jena-arq/src/main/java/org/apache/jena/riot/RDFParser.java
@@ -36,6 +36,7 @@
 import org.apache.jena.atlas.web.ContentType;
 import org.apache.jena.atlas.web.TypedInputStream;
 import org.apache.jena.graph.Graph;
+import org.apache.jena.irix.IRIs;
 import org.apache.jena.irix.IRIxResolver;
 import org.apache.jena.query.Dataset;
 import org.apache.jena.rdf.model.Model;
@@ -446,12 +447,17 @@
         } else {
             if ( ! strict )
                 checking$ = checking.orElseGet(()->true);
+            // Languages, like Turtle, where the base defaults to the system base.
+            // Setting the resolver directly overrides this.
+            if ( baseStr == null && resolve )
+                baseStr = IRIs.getBaseStr();
         }
         if ( sameLang(RDFJSON, lang) )
             // The JSON-LD subsystem handles this.
             resolve = false;
 
-        IRIxResolver parserResolver = (resolver != null) ? resolver
+        IRIxResolver parserResolver = (resolver != null)
+                ? resolver
                 : IRIxResolver.create().base(baseStr).resolve(resolve).allowRelative(allowRelative).build();
         PrefixMap prefixMap = PrefixMapFactory.create();
         ParserProfileStd parserFactory = new ParserProfileStd(factory, errorHandler,
diff --git a/jena-arq/src/main/java/org/apache/jena/riot/lang/CollectorStreamRDF.java b/jena-arq/src/main/java/org/apache/jena/riot/lang/CollectorStreamRDF.java
index 2964be6..f25e66b 100644
--- a/jena-arq/src/main/java/org/apache/jena/riot/lang/CollectorStreamRDF.java
+++ b/jena-arq/src/main/java/org/apache/jena/riot/lang/CollectorStreamRDF.java
@@ -28,7 +28,7 @@
 import org.apache.jena.sparql.core.Quad ;
 
 /**
- * StreamRDF implementations which store received triples and quads
+ * StreamRDF implementations which stores received triples and quads
  * in a {@link java.util.Collection}.
  *
  * The resulting collection can be retrieved via the
diff --git a/jena-arq/src/main/java/org/apache/jena/riot/system/Checker.java b/jena-arq/src/main/java/org/apache/jena/riot/system/Checker.java
index a7cb727..9fe0512 100644
--- a/jena-arq/src/main/java/org/apache/jena/riot/system/Checker.java
+++ b/jena-arq/src/main/java/org/apache/jena/riot/system/Checker.java
@@ -29,8 +29,10 @@
 import org.apache.jena.iri.IRI;
 import org.apache.jena.iri.IRIComponents;
 import org.apache.jena.iri.Violation;
+import org.apache.jena.irix.IRIProviderJenaIRI;
 import org.apache.jena.irix.IRIs;
 import org.apache.jena.irix.SetupJenaIRI;
+import org.apache.jena.irix.SystemIRIx;
 import org.apache.jena.sparql.core.Quad;
 import org.apache.jena.sparql.graph.NodeConst;
 import org.apache.jena.util.SplitIRI;
@@ -121,8 +123,10 @@
     public static boolean iriViolations(IRI iri, ErrorHandler errorHandler,
                                         boolean allowRelativeIRIs, boolean includeIRIwarnings,
                                         long line, long col) {
+
         if ( !allowRelativeIRIs && iri.isRelative() )
-            errorHandler(errorHandler).error("Relative IRI: " + iri, line, col);
+            // Relative IRIs.
+            iriViolationMessage(iri.toString(), true, "Relative IRI: " + iri, line, col, errorHandler);
 
         boolean isOK = true;
 
@@ -134,26 +138,47 @@
                 int code = v.getViolationCode();
                 boolean isError = v.isError();
 
-                // Anything we want to reprioritise?
+                // --- Tune warnings.
+                // IRIProviderJena filters ERRORs and throws an exception on error.
+                // It can't add warnings or remove them at that point.
+                // Do WARN filtering here.
                 if ( code == Violation.LOWERCASE_PREFERRED && v.getComponent() != IRIComponents.SCHEME ) {
-                    // Issue warning about the scheme part. Not e.g. DNS names.
+                    // Issue warning about the scheme part only. Not e.g. DNS names.
                     continue;
                 }
+
+                // Convert selected violations from ERROR to WARN for output/
+                // There are cases where jena-iri always makes a violation an ERROR regardless of SetupJenaIRI
+                // PROHIBITED_COMPONENT_PRESENT
+//                if ( code == Violation.PROHIBITED_COMPONENT_PRESENT )
+//                    isError = false;
+
+                isOK = false;
                 String msg = v.getShortMessage();
                 String iriStr = iri.toString();
-
-                errorHandler(errorHandler).warning("Bad IRI: " + msg, line, col);
-
-//                if ( isError )
-//                    errorHandler(errorHandler).warning("Bad IRI: " + msg, line, col);
-//                else
-//                    errorHandler(errorHandler).warning("Not advised IRI: " + msg, line, col);
-                isOK = true;
+                iriViolationMessage(iriStr, isError, msg, line, col, errorHandler);
             }
         }
         return isOK;
     }
 
+    /**
+     * Common handling messages about IRIs during parsing whether a violation or an
+     * IRIException. Prints a warning, with different messages for IRI error or warning.
+     */
+    public static void iriViolationMessage(String iriStr, boolean isError, String msg, long line, long col, ErrorHandler errorHandler) {
+        try {
+            if ( ! ( SystemIRIx.getProvider() instanceof IRIProviderJenaIRI ) )
+                msg = "<" + iriStr + "> : " + msg;
+
+            if ( isError ) {
+                // ?? Treat as error, catch exceptions?
+                errorHandler(errorHandler).warning("Bad IRI: " + msg, line, col);
+            } else
+                errorHandler(errorHandler).warning("Not advised IRI: " + msg, line, col);
+        } catch (org.apache.jena.iri.IRIException | org.apache.jena.irix.IRIException ex) {}
+    }
+
     // ==== Literals
 
     final static private Pattern langPattern = Pattern.compile("[a-zA-Z]{1,8}(-[a-zA-Z0-9]{1,8})*");
diff --git a/jena-arq/src/main/java/org/apache/jena/riot/system/ErrorHandlerFactory.java b/jena-arq/src/main/java/org/apache/jena/riot/system/ErrorHandlerFactory.java
index 197acc8..28eafbe 100644
--- a/jena-arq/src/main/java/org/apache/jena/riot/system/ErrorHandlerFactory.java
+++ b/jena-arq/src/main/java/org/apache/jena/riot/system/ErrorHandlerFactory.java
@@ -66,7 +66,8 @@
     public static ErrorHandler errorHandlerSimple()                 { return new ErrorHandlerSimple() ; }
 
     /** Logs warnings and errors while tracking the counts of each and optionally throwing exceptions when errors and/or warnings are encounted */
-    public static ErrorHandlerTracking errorHandlerTracking(Logger log, boolean failOnError, boolean failOnWarning) { return new ErrorHandlerTracking(log, failOnError, failOnWarning); }
+    public static ErrorHandlerTracking errorHandlerTracking(Logger log, boolean failOnError, boolean failOnWarning)
+    { return new ErrorHandlerTracking(log, failOnError, failOnWarning); }
 
     /**
      * An error handler that throws a {@link RiotParseException}, hence it
diff --git a/jena-arq/src/main/java/org/apache/jena/riot/system/ParserProfileStd.java b/jena-arq/src/main/java/org/apache/jena/riot/system/ParserProfileStd.java
index 165ea1f..a3f3d3a 100644
--- a/jena-arq/src/main/java/org/apache/jena/riot/system/ParserProfileStd.java
+++ b/jena-arq/src/main/java/org/apache/jena/riot/system/ParserProfileStd.java
@@ -34,26 +34,24 @@
 import org.apache.jena.sparql.util.FmtUtils;
 
 /**
- * {@link ParserProfileStd} uses a {@link FactoryRDF} to
- * create items in the parsing process.
+ * {@link ParserProfileStd} uses a {@link FactoryRDF} to create items in the parsing
+ * process.
  */
-public class ParserProfileStd implements ParserProfile
-{
-    private final FactoryRDF   factory;
+public class ParserProfileStd implements ParserProfile {
+    private final FactoryRDF factory;
     private final ErrorHandler errorHandler;
-    private final Context      context;
-    private       IRIxResolver resolver;
-    private final PrefixMap    prefixMap;
-    private final boolean      strictMode;
-    private final boolean      checking;
+    private final Context context;
+    private IRIxResolver resolver;
+    private final PrefixMap prefixMap;
+    private final boolean strictMode;
+    private final boolean checking;
     private static int DftCacheSize = 500;
     private final Cache<String, IRI> iriCache;
 
     private boolean allowNodeExtentions;
 
-    public ParserProfileStd(FactoryRDF factory, ErrorHandler errorHandler,
-                            IRIxResolver resolver, PrefixMap prefixMap,
-                            Context context, boolean checking, boolean strictMode) {
+    public ParserProfileStd(FactoryRDF factory, ErrorHandler errorHandler, IRIxResolver resolver, PrefixMap prefixMap, Context context,
+                            boolean checking, boolean strictMode) {
         this.factory = factory;
         this.errorHandler = errorHandler;
         this.resolver = resolver;
@@ -62,7 +60,7 @@
         this.checking = checking;
         this.iriCache = checking ? CacheFactory.createCache(DftCacheSize) : null;
         this.strictMode = strictMode;
-        this.allowNodeExtentions = true; //(context.isTrue(RIOT.ALLOW_NODE_EXT)) ;
+        this.allowNodeExtentions = true; // (context.isTrue(RIOT.ALLOW_NODE_EXT)) ;
     }
 
     @Override
@@ -98,21 +96,20 @@
             return IRIx.createAny(uriStr);
         }
 
+        // Relative IRIs.
+        // jena-iri : these are errors on the
         try {
             IRIx iri = resolver.resolve(uriStr);
             if ( checking )
                 doChecking(iri, iri.str(), line, col);
             return iri;
+        } catch (RelativeIRIException ex ) {
+            errorHandler.error("Relative IRI: " + uriStr, line, col);
+            return IRIx.createAny(uriStr);
         } catch (IRIException ex) {
-            // This should only be errors and the errorHandler may be set to "don't continue".
-            // if it does continue, assume it prints something.
-            if ( SystemIRIx.getProvider() instanceof IRIProviderJenaIRI )
-                // Checking using JenaIRI puts the URI string in the message.
-                // Puts the IRI in the message.
-                errorHandler.error("Bad IRI: "+ex.getMessage(), line, col);
-            else
-                // Does not put the IRI in the message.
-                errorHandler.error("Bad IRI: <" + uriStr + "> : "+ex.getMessage(), line, col);
+            // Same code as Checker.iriViolations
+            String msg = ex.getMessage();
+            Checker.iriViolationMessage(uriStr, true, msg, line, col, errorHandler);
             return IRIx.createAny(uriStr);
         }
     }
@@ -122,11 +119,14 @@
         if ( irix instanceof IRIProviderJenaIRI.IRIxJena )
             iri = (IRI)irix.getImpl();
         else
-            iri = iriCache.getOrFill(uriStr, ()->SetupJenaIRI.iriCheckerFactory().create(uriStr));
+            iri = iriCache.getOrFill(uriStr, () -> SetupJenaIRI.iriCheckerFactory().create(uriStr));
         Checker.iriViolations(iri, errorHandler, false, true, line, col);
     }
 
-    /** Create a triple - this operation call {@link #checkTriple} if checking is enabled. */
+    /**
+     * Create a triple - this operation call {@link #checkTriple} if checking is
+     * enabled.
+     */
     @Override
     public Triple createTriple(Node subject, Node predicate, Node object, long line, long col) {
         if ( checking )
@@ -140,7 +140,7 @@
 
     protected void checkTriple(Node subject, Node predicate, Node object, long line, long col) {
         if ( subject == null || (!subject.isURI() && !subject.isBlank()) ) {
-            if ( ! allowSpecialNode(subject) ) {
+            if ( !allowSpecialNode(subject) ) {
                 errorHandler.error("Subject is not a URI or blank node", line, col);
                 throw new RiotException("Bad subject: " + subject);
             }
@@ -150,14 +150,17 @@
             throw new RiotException("Bad predicate: " + predicate);
         }
         if ( object == null || (!object.isURI() && !object.isBlank() && !object.isLiteral()) ) {
-            if ( ! allowSpecialNode(object) ) {
+            if ( !allowSpecialNode(object) ) {
                 errorHandler.error("Object is not a URI, blank node or literal", line, col);
                 throw new RiotException("Bad object: " + object);
             }
         }
     }
 
-    /** Create a quad - this operation call {@link #checkTriple} if checking is enabled. */
+    /**
+     * Create a quad - this operation call {@link #checkTriple} if checking is
+     * enabled.
+     */
     @Override
     public Quad createQuad(Node graph, Node subject, Node predicate, Node object, long line, long col) {
         if ( checking )
@@ -177,8 +180,8 @@
     @Override
     public Node createURI(String x, long line, long col) {
         // Special cases that don't resolve.
-        //   <_:....> is a blank node.
-        //   <::...> is "don't touch" used for a fixed-up prefix name
+        // <_:....> is a blank node.
+        // <::...> is "don't touch" used for a fixed-up prefix name
         if ( !RiotLib.isBNodeIRI(x) && !RiotLib.isPrefixIRI(x) )
             // Really is an URI!
             x = resolveIRI(x, line, col);
diff --git a/jena-arq/src/test/java/org/apache/jena/arq/junit/manifest/Manifest.java b/jena-arq/src/test/java/org/apache/jena/arq/junit/manifest/Manifest.java
index 095f4e3..c1458b4 100644
--- a/jena-arq/src/test/java/org/apache/jena/arq/junit/manifest/Manifest.java
+++ b/jena-arq/src/test/java/org/apache/jena/arq/junit/manifest/Manifest.java
@@ -65,7 +65,6 @@
         }
     }
 
-
     private Manifest(String fn) {
         filename = IRILib.filenameToIRI(fn) ;
         manifest = RDFDataMgr.loadModel(filename) ;
diff --git a/jena-arq/src/test/java/org/apache/jena/arq/junit/riot/RiotSyntaxTest.java b/jena-arq/src/test/java/org/apache/jena/arq/junit/riot/RiotSyntaxTest.java
index 24b5ebb..35042ba 100644
--- a/jena-arq/src/test/java/org/apache/jena/arq/junit/riot/RiotSyntaxTest.java
+++ b/jena-arq/src/test/java/org/apache/jena/arq/junit/riot/RiotSyntaxTest.java
@@ -21,6 +21,7 @@
 import static org.junit.Assert.fail;
 
 import org.apache.jena.arq.junit.manifest.ManifestEntry;
+import org.apache.jena.atlas.io.IO;
 import org.apache.jena.atlas.lib.FileOps;
 import org.apache.jena.atlas.lib.IRILib;
 import org.apache.jena.riot.Lang ;
@@ -56,8 +57,13 @@
         }
         try {
             ParseForTest.parse(stream, filename, lang);
-            if (! expectLegalSyntax )
+            if (! expectLegalSyntax ) {
+                String s = IO.readWholeFileAsUTF8(fn);
+                System.err.println();
+                System.err.println("== "+filename);
+                System.err.print(s);
                 fail("Parsing succeeded in a bad syntax test");
+            }
         } catch(RiotNotFoundException ex) {
             throw ex;
         } catch(RiotException ex) {
diff --git a/jena-arq/src/test/java/org/apache/jena/riot/lang/TestLangNTriples.java b/jena-arq/src/test/java/org/apache/jena/riot/lang/TestLangNTriples.java
index 3d378cf..940f9c9 100644
--- a/jena-arq/src/test/java/org/apache/jena/riot/lang/TestLangNTriples.java
+++ b/jena-arq/src/test/java/org/apache/jena/riot/lang/TestLangNTriples.java
@@ -35,7 +35,7 @@
 import org.apache.jena.sparql.sse.SSE ;
 import org.junit.Test ;
 
-/** Test of syntax by a triples parser (does not include node validitiy checking) */
+/** Test of syntax by a triples parser (does not include node validity checking) */
 
 public class TestLangNTriples extends AbstractTestLangNTuples
 {
diff --git a/jena-arq/src/test/java/org/apache/jena/riot/lang/TestLangTurtle.java b/jena-arq/src/test/java/org/apache/jena/riot/lang/TestLangTurtle.java
index 47b2eb5..3a13aea 100644
--- a/jena-arq/src/test/java/org/apache/jena/riot/lang/TestLangTurtle.java
+++ b/jena-arq/src/test/java/org/apache/jena/riot/lang/TestLangTurtle.java
@@ -160,10 +160,10 @@
     @Test(expected=ExError.class)
     public void errorBadURI_1()         { parse("<http://example/a b> <http://example/p> 123 .") ; }
 
-    @Test(expected=ExError.class)
+    @Test(expected=ExWarning.class)
     public void errorBadURI_2()         { parse("<http://example/a%XAb> <http://example/p> 123 .") ; }
 
-    @Test //(expected=ExWarning.class)
+    @Test
     public void errorBadURI_3()         { parse("<http://example/a%Aab> <http://example/p> 123 .") ; }
 
     // Bad URIs
diff --git a/jena-arq/src/test/java/org/apache/jena/riot/lang/CatchParserOutput.java b/jena-arq/src/test/java/org/apache/jena/riot/system/CatchParserOutput.java
similarity index 77%
rename from jena-arq/src/test/java/org/apache/jena/riot/lang/CatchParserOutput.java
rename to jena-arq/src/test/java/org/apache/jena/riot/system/CatchParserOutput.java
index ed1cb95..d70b543 100644
--- a/jena-arq/src/test/java/org/apache/jena/riot/lang/CatchParserOutput.java
+++ b/jena-arq/src/test/java/org/apache/jena/riot/system/CatchParserOutput.java
@@ -16,26 +16,25 @@
  * limitations under the License.
  */
 
-package org.apache.jena.riot.lang;
+package org.apache.jena.riot.system;
 
 import java.util.ArrayList;
 import java.util.List;
 
 import org.apache.jena.atlas.lib.Pair;
 import org.apache.jena.graph.Triple;
-import org.apache.jena.riot.system.StreamRDF;
 import org.apache.jena.sparql.core.Quad;
 
-class CatchParserOutput implements StreamRDF
+public class CatchParserOutput implements StreamRDF
 {
-    List<Triple>      triples     = new ArrayList<>() ;
-    List<Quad>        quads       = new ArrayList<>() ;
-    List<Pair<String,String>>     prefixes     = new ArrayList<>() ;
-    List<String>     bases       = new ArrayList<>() ;
+    public List<Triple>      triples     = new ArrayList<>() ;
+    public List<Quad>        quads       = new ArrayList<>() ;
+    public List<Pair<String,String>>     prefixes     = new ArrayList<>() ;
+    public List<String>     bases       = new ArrayList<>() ;
 
-    int startCalled = 0 ;
+    public int startCalled = 0 ;
 
-    int finishCalled = 0 ;
+    public int finishCalled = 0 ;
 
     @Override public void start()   { startCalled++ ; }
 
diff --git a/jena-arq/src/test/java/org/apache/jena/riot/system/TS_RiotSystem.java b/jena-arq/src/test/java/org/apache/jena/riot/system/TS_RiotSystem.java
index 4f77e8b..c49b175 100644
--- a/jena-arq/src/test/java/org/apache/jena/riot/system/TS_RiotSystem.java
+++ b/jena-arq/src/test/java/org/apache/jena/riot/system/TS_RiotSystem.java
@@ -44,6 +44,7 @@
     , TestFormatRegistration.class
     , TestJsonLDReadWrite.class         // Some simple testing of the jsonld-java engine.
     , TestSerializable.class
+    , TestIRIxRIOT.class
 })
 
 public class TS_RiotSystem
diff --git a/jena-arq/src/test/java/org/apache/jena/riot/system/TestChecker.java b/jena-arq/src/test/java/org/apache/jena/riot/system/TestChecker.java
index 63d7549..caeb426 100644
--- a/jena-arq/src/test/java/org/apache/jena/riot/system/TestChecker.java
+++ b/jena-arq/src/test/java/org/apache/jena/riot/system/TestChecker.java
@@ -20,7 +20,6 @@
 
 import org.apache.jena.graph.Node ;
 import org.apache.jena.riot.ErrorHandlerTestLib ;
-import org.apache.jena.riot.ErrorHandlerTestLib.ExError ;
 import org.apache.jena.riot.ErrorHandlerTestLib.ExWarning ;
 import org.apache.jena.shared.impl.JenaParameters ;
 import org.apache.jena.sparql.util.NodeFactoryExtra ;
@@ -49,7 +48,7 @@
     @Test
     public void checker_uri_01()    { check("<http://example/x>") ; }
 
-    @Test(expected=ExError.class)
+    @Test(expected=ExWarning.class)
     public void checker_uri_02()    { check("<x>") ; }
 
     @Test (expected=ExWarning.class)
diff --git a/jena-arq/src/test/java/org/apache/jena/riot/system/TestIRIxRIOT.java b/jena-arq/src/test/java/org/apache/jena/riot/system/TestIRIxRIOT.java
new file mode 100644
index 0000000..dd1d50a
--- /dev/null
+++ b/jena-arq/src/test/java/org/apache/jena/riot/system/TestIRIxRIOT.java
@@ -0,0 +1,260 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.jena.riot.system;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assume.assumeTrue;
+
+import java.io.ByteArrayInputStream;
+import java.io.InputStream;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+
+import org.apache.jena.atlas.lib.Bytes;
+import org.apache.jena.irix.IRIs;
+import org.apache.jena.irix.IRIxResolver;
+import org.apache.jena.riot.Lang;
+import org.apache.jena.riot.RDFParser;
+import org.apache.jena.riot.RDFParserBuilder;
+import org.apache.jena.riot.RiotException;
+import org.junit.FixMethodOrder;
+import org.junit.Test;
+import org.junit.runners.MethodSorters;
+
+/** Test IRIx in parser usage. */
+@FixMethodOrder(MethodSorters.NAME_ASCENDING)
+public class TestIRIxRIOT {
+
+    // The cases:
+    // _nt        ::  N-triples, default configuration.
+    // _nt_check  ::  N-triples, with checking.
+    // _ttl       :: Turtle, default configuration (which is checking).
+
+    @Test public void irix_http_1_nt()          { testDft("<http://example/>", Lang.NT, 0, 0); }
+    @Test public void irix_http_1_nt_check()    { testNT("<http://example/>", TRUE, UNSET, 0, 0); }
+    @Test public void irix_http_1_ttl()         { testDft("<http://example/>", Lang.TTL, 0, 0); }
+
+    @Test public void irix_http_2_nt()          { testDft("<HTTP://example/>", Lang.NT, 0, 0); }
+    @Test public void irix_http_2_nt_check()    { testLang("<HTTP://example/>", Lang.NT, UNSET, TRUE, 0, 1); }
+    @Test public void irix_http_2_ttl()         { testDft("<HTTP://example/>", Lang.TTL, 0, 1); }
+
+    @Test public void irix_http_3_nt()          { testDft("<http://EXAMPLE/>", Lang.NT, 0, 0); }
+    @Test public void irix_http_3_nt_check()    { testLang("<http://EXAMPLE/>", Lang.NT, UNSET, TRUE, 0, 0); }
+    @Test public void irix_http_3_ttl()         { testDft("<http://EXAMPLE/>", Lang.TTL, 0, 0); }
+
+    @Test public void irix_http_4_nt()          { testDft("<http://user:pw@host/>", Lang.NT, 0, 0); }
+    @Test public void irix_http_4_nt_check()    { testLang("<http://user:pw@host/>", Lang.NT, UNSET, TRUE, 0, 2); }
+    @Test public void irix_http_4_ttl()         { testDft("<http://user:pw@host/>", Lang.TTL, 0, 2); }
+
+    @Test public void irix_uuid_1_nt()          { testDft("<urn:uuid:6cd401dc-a8d2-11eb-9192-1f162b53dc79>", Lang.NT, 0, 0); }
+    @Test public void irix_uuid_1_nt_check()    { testLang("<urn:uuid:6cd401dc-a8d2-11eb-9192-1f162b53dc79>", Lang.NT, UNSET, TRUE, 0, 0); }
+    @Test public void irix_uuid_1_ttl()         { testDft("<urn:uuid:6cd401dc-a8d2-11eb-9192-1f162b53dc79>", Lang.TTL, 0, 0); }
+
+    @Test public void irix_uuid_2_nt()          { testDft("<urn:uuid:bad>", Lang.NT, 0, 1); }
+    @Test public void irix_uuid_2_nt_check()    { testLang("<urn:uuid:bad>", Lang.NT, UNSET, TRUE, 0, 1); }
+    @Test public void irix_uuid_2_ttl()         { testDft("<urn:uuid:bad>", Lang.TTL, 0, 1); }
+
+    @Test public void irix_uuid_3_nt()          { testDft("<urn:uuid:bad>", Lang.NT, 0, 1); }
+    @Test public void irix_uuid_3_nt_check()    { testLang("<urn:uuid:bad>", Lang.NT, UNSET, TRUE, 0, 1); }
+    @Test public void irix_uuid_3_ttl()         { testDft("<urn:uuid:bad>", Lang.TTL, 0, 1); }
+
+    @Test public void irix_uuid_4_nt()          { testDft("<uuid:bad>", Lang.NT, 0, 1); }
+    @Test public void irix_uuid_4_nt_check()    { testLang("<uuid:bad>", Lang.NT, UNSET, TRUE, 0, 1); }
+    @Test public void irix_uuid_4_ttl()         { testDft("<uuid:bad>", Lang.TTL, 0, 1); }
+
+    @Test public void irix_urn_1_nt()           { testDft("<urn:ab:c>", Lang.NT, 0, 0); }
+    @Test public void irix_urn_1_nt_check()     { testLang("<urn:ab:c>", Lang.NT, UNSET, TRUE, 0, 0); }
+    @Test public void irix_urn_1_ttl()          { testDft("<urn:ab:c>", Lang.TTL, 0, 0); }
+
+    // URNs are required to have 2+ character NID : RFC 8141
+    @Test public void irix_urn_2_nt()           { testDft("<urn:x:c>", Lang.NT, 0, 0); }
+    @Test public void irix_urn_2_nt_check()     { testLang("<urn:x:c>", Lang.NT, UNSET, TRUE, 0, 1); }
+    @Test public void irix_urn_2_ttl()          { testDft("<urn:x:c>", Lang.TTL, 0, 1); }
+
+    @Test public void irix_urn_3_nt()           { testDft("<urn:00:c>", Lang.NT, 0, 0); }
+    @Test public void irix_urn_3_nt_check()     { testLang("<urn:00:c>", Lang.NT, UNSET, TRUE, 0, 0); }
+    @Test public void irix_urn_3_ttl()          { testDft("<urn:00:c>", Lang.TTL, 0, 0); }
+
+    // URIs
+    @Test public void irix_err_1_nt()           { testDft("<http://host/bad path/>", Lang.NT, 1, 1); }
+    @Test public void irix_err_1_nt_check()     { testLang("<http://host/bad path/>", Lang.NT, UNSET, TRUE, 1, 1); }
+    @Test public void irix_err_1_ttl()          { testDft("<http://host/bad path/>", Lang.TTL, 1, 1); }
+
+    // NT: Relative URI
+    @Test public void irix_relative_nt()           { testNT("<relative>", UNSET, UNSET, 0, 0); }
+    @Test public void irix_relative_nt_check()     { testNT("<relative>", UNSET, TRUE, 0, 1); }
+    @Test public void irix_relative_nt_strict()    { testNT("<relative>", TRUE, UNSET, 1, 0); }
+    @Test public void irix_relative_nt_strict_check()    { testNT("<relative>", TRUE, TRUE, 1, 0); }
+    @Test public void irix_relative_nt_strict_nocheck()   { testNT("<relative>", TRUE, FALSE, 1, 0); }
+
+    // -------- Special cases for Turtle.
+    // Turtle - base defaults to system base in normal use.
+
+    @Test
+    public void irix_relative_3_ttl() {
+        assumeTrue(IRIs.getBaseStr() != null);
+        testTTL("<relative>", UNSET, UNSET, 0, 0);
+    }
+
+    // Turtle with directly set resolver, non-standard setup. no base, resolve, no relative IRIs
+    @Test public void irix_ttl_resolver_0() {
+        // Resolver:: default is allowRelative(true)
+        IRIxResolver resolver = IRIxResolver.create().noBase().build();
+        testTTL("<relative>", resolver, 0, 1);
+    }
+
+    @Test public void irix_ttl_resolver_1() {
+        // Resolver:: no base, no relative IRIs -> error.
+        IRIxResolver resolver = IRIxResolver.create().noBase().allowRelative(false).build();
+        testTTL("<relative>", resolver, 1, 0);
+    }
+
+    // Turtle with directly set resolver, non-standard setup. No base, no resolve, no relative IRIs.
+    @Test public void irix_ttl_resolver_2() {
+        // Resolver:: no base, no relative IRIs, no resolving -> error.
+        IRIxResolver resolver = IRIxResolver.create().noBase().resolve(false).allowRelative(false).build();
+        testTTL("<relative>", resolver, 1, 0);
+    }
+
+    @Test public void irix_ttl_resolver_3() {
+        // Resolver:: no base, allow relative IRIs -> warning.
+        IRIxResolver resolver = IRIxResolver.create().noBase().resolve(true).allowRelative(true).build();
+        testTTL("<relative>", resolver, 0, 1);
+    }
+
+    @Test public void irix_ttl_resolver_4() {
+        // Resolver:: no base, allow relative IRIs, no resolving -> warning.
+        IRIxResolver resolver = IRIxResolver.create().noBase().resolve(false).allowRelative(true).build();
+        testTTL("<relative>", resolver, 0, 1);
+    }
+
+    @Test public void irix_ttl_resolver_5() {
+        // Resolver:: no base, allow relative IRIs, no resolving -> warning.
+        IRIxResolver resolver = IRIxResolver.create().noBase().resolve(false).allowRelative(true).build();
+        testTTL("<relative>", resolver, 0, 1);
+    }
+
+    // --------
+
+    private static final Optional<Boolean> TRUE  = Optional.of(true);
+    private static final Optional<Boolean> FALSE = Optional.of(false);
+    private static final Optional<Boolean> UNSET = Optional.empty();
+
+    // Default behaviour of Lang.
+    private static void testDft(String iri, Lang lang, int numErrors, int numWarnings) {
+        testLang(iri, lang, /*base*/null, UNSET, UNSET, numErrors, numWarnings);
+    }
+
+    // Behaviour of Lang, toegther with settable strict and checking.
+    private static void testLang(String iri, Lang lang, Optional<Boolean> strict, Optional<Boolean> checking, int numErrors, int numWarnings) {
+        testLang(iri, lang, /*base*/null, strict, checking, numErrors, numWarnings);
+    }
+
+    // N-triples
+    private static void testNT(String iri, Optional<Boolean> strict, Optional<Boolean> checking, int numErrors, int numWarnings) {
+        testLang(iri, Lang.NT, /*base*/null, strict, checking, numErrors, numWarnings);
+    }
+
+    // Turtle, with base.
+    private static void testTTL(String iri, Optional<Boolean> strict, Optional<Boolean> checking, int numErrors, int numWarnings) {
+        testLang(iri, Lang.TTL, "http://base/", strict, checking, numErrors, numWarnings);
+    }
+
+    // Turtle, with resolver
+    private static void testTTL(String iri, IRIxResolver resolver, int numErrors, int numWarnings) {
+        InputStream in = generateSource(iri);
+        RDFParserBuilder builder = RDFParser.source(in).forceLang(Lang.TTL).resolver(resolver);
+        runTest(builder, iri, numErrors, numWarnings);
+    }
+
+    private static void testLang(String iri, Lang lang, String base, Optional<Boolean> strict, Optional<Boolean> checking, int numErrors, int numWarnings) {
+        InputStream in = generateSource(iri);
+        RDFParserBuilder builder = RDFParser.source(in).forceLang(lang);
+        builder.base(base);
+        if ( strict.isPresent() )
+            builder.strict(strict.get());
+        if ( checking.isPresent() )
+            builder.checking(checking.get());
+        runTest(builder, iri, numErrors, numWarnings);
+    }
+
+    private static void runTest(RDFParserBuilder builder, String iri, int numErrors, int numWarnings) {
+        StreamRDF dest = new CatchParserOutput();
+        ErrorHandlerCollector eh = new ErrorHandlerCollector();
+        builder.errorHandler(eh);
+
+        // Do it!
+        builder.build().parse(dest);
+
+        int numErrorsActual = eh.errors.size();
+        int numWarningsActual = eh.warnings.size();
+
+        String msg = "Errors=("+numErrors+",got="+numErrorsActual+") Warnings=("+numWarnings+",got="+numWarningsActual+")";
+
+        if ( numErrors != numErrorsActual || numWarnings != numWarningsActual ) {
+            System.err.println("== "+iri);
+            System.err.println("-- "+msg);
+            if ( numErrorsActual == 0 )
+                System.err.println("Errors: None");
+            else
+                eh.errors.forEach(m->System.err.println("Error: "+m));
+            if ( numWarningsActual == 0 && numWarnings >= 0 )
+                System.err.println("Warnings: None");
+            else
+                eh.warnings.forEach(m->System.err.println("Warnings: "+m));
+        }
+
+        assertEquals("Errors ("+msg+")", numErrors, numErrorsActual);
+        // Only tested if errors passes.
+        // -1 => ignore
+        if ( numWarnings >= 0 )
+            assertEquals("Warnings ("+msg+")", numWarnings, numWarningsActual);
+    }
+
+    private static InputStream generateSource(String iri) {
+        // N-Triples line with test subject
+        String TEXT = iri+" <x:p> <x:o> .";
+        InputStream inText = new ByteArrayInputStream(Bytes.string2bytes(TEXT));
+        return inText;
+    }
+
+    static class ErrorHandlerCollector implements ErrorHandler {
+        List<String> warnings = new ArrayList<>();
+        List<String> errors = new ArrayList<>();
+        List<String> fatals = new ArrayList<>();
+
+        @Override
+        public void warning(String message, long line, long col) {
+            warnings.add(message);
+        }
+
+        @Override
+        public void error(String message, long line, long col) {
+            errors.add(message);
+            //throw new RiotException(message);
+        }
+
+        @Override
+        public void fatal(String message, long line, long col) {
+            fatals.add(message);
+            throw new RiotException(message);
+        }
+    }
+}
diff --git a/jena-base/src/main/java/org/apache/jena/atlas/lib/EscapeStr.java b/jena-base/src/main/java/org/apache/jena/atlas/lib/EscapeStr.java
index 7d780e5..a6c3455 100644
--- a/jena-base/src/main/java/org/apache/jena/atlas/lib/EscapeStr.java
+++ b/jena-base/src/main/java/org/apache/jena/atlas/lib/EscapeStr.java
@@ -145,7 +145,7 @@
 
     /** Unicode escapes  \-u and \-U only */
     public static String unescapeUnicode(String s) {
-        return  unescape(s, '\\', true) ;
+        return unescape(s, '\\', true) ;
     }
 
     // Main worker function for unescaping strings.
diff --git a/jena-base/src/main/java/org/apache/jena/atlas/lib/StrUtils.java b/jena-base/src/main/java/org/apache/jena/atlas/lib/StrUtils.java
index c771acf..5ad6a9d 100644
--- a/jena-base/src/main/java/org/apache/jena/atlas/lib/StrUtils.java
+++ b/jena-base/src/main/java/org/apache/jena/atlas/lib/StrUtils.java
@@ -35,7 +35,7 @@
 public class StrUtils //extends StringUtils
 {
     private StrUtils() {}
-    
+
     /** strjoin with a newline as the separator */
     public static String strjoinNL(String... args) {
         return String.join("\n", args);
@@ -56,10 +56,10 @@
     public static final int CMP_GREATER  = +1 ;
     public static final int CMP_EQUAL    =  0 ;
     public static final int CMP_LESS     = -1 ;
-    
+
     public static final int CMP_UNEQUAL  = -9 ;
     public static final int CMP_INDETERMINATE  = 2 ;
-    
+
     public static int strCompare(String s1, String s2) {
         // Value is the difference of the first differing chars
         int x = s1.compareTo(s2) ;
@@ -68,7 +68,7 @@
         if ( x == 0 ) return CMP_EQUAL ;
         throw new InternalErrorException("String comparison failure") ;
     }
-    
+
     public static int strCompareIgnoreCase(String s1, String s2) {
         // x is the difference of the first differing chars
         int x = s1.compareToIgnoreCase(s2) ;
@@ -78,14 +78,22 @@
         throw new InternalErrorException("String comparison failure") ;
     }
 
+    public static boolean strStartsWithIgnoreCase(String str, String prefix) {
+        return str.regionMatches(true, 0, prefix, 0, prefix.length());
+    }
+
+    public static boolean strEndsWithIgnoreCase(String str, String suffix) {
+        return str.regionMatches(true, str.length()-suffix.length(), suffix, 0, suffix.length());
+    }
+
     public static byte[] asUTF8bytes(String s) {
-        return s.getBytes(UTF_8) ; 
+        return s.getBytes(UTF_8) ;
     }
 
     public static String fromUTF8bytes(byte[] bytes) {
-        return new String(bytes, UTF_8) ; 
+        return new String(bytes, UTF_8) ;
     }
-    
+
     /**
      * @param x
      * @return &lt;null&gt; if x == null, otherwise, x.toString()
@@ -98,10 +106,10 @@
     public static String[] split(String s, String splitStr) {
         return stream(s.split(splitStr)).map(String::trim).toArray(String[]::new) ;
     }
-    
+
     /**
      * Does one string contain another string?
-     * 
+     *
      * @param str1
      * @param str2
      * @return true if str1 contains str2
@@ -109,7 +117,7 @@
     public final static boolean contains(String str1, String str2) {
         return str1.contains(str2) ;
     }
-    
+
     public final static String replace(String string, String target, String replacement) {
         return string.replace(target, replacement) ;
     }
@@ -117,12 +125,12 @@
     public static String substitute(String str, Map<String, String> subs) {
         for ( Map.Entry<String, String> e : subs.entrySet() ) {
             String param = e.getKey() ;
-            if ( str.contains(param) ) 
+            if ( str.contains(param) )
                 str = str.replace(param, e.getValue()) ;
         }
         return str ;
     }
-    
+
     public static String strform(Map<String, String> subs, String... args) {
         return substitute(strjoinNL(args), subs) ;
     }
@@ -136,20 +144,20 @@
             x = StrUtils.chop(x) ;
         return x ;
     }
-    
+
     public static List<Character> toCharList(String str) {
         return str.codePoints().mapToObj(i -> (char) i).map(Character::valueOf).collect(toList());
     }
-    
+
     // ==== Encoding and decoding strings based on a marker character (e.g. %)
-    // and then the hexadecimal representation of the character.  
+    // and then the hexadecimal representation of the character.
     // Only characters 0-255 can be encoded.
     // Decoding is more general.
-    
+
     /**
      * Encode a string using hex values e.g. %20.
-     * Encoding only deals with single byte codepoints.  
-     * 
+     * Encoding only deals with single byte codepoints.
+     *
      * @param str String to encode
      * @param marker Marker character
      * @param escapees Characters to encode (must include the marker)
@@ -189,7 +197,7 @@
     /**
      * Decode a string using marked hex values e.g. %20.
      * Multi-byte UTF-8 codepoints are handled.
-     * 
+     *
      * @param str String to decode.
      * @param marker The marker character
      * @return Decoded string (returns input object if no change)
@@ -198,7 +206,7 @@
         if ( str.indexOf(marker) < 0 )
             // No marker, no work.
             return str;
-        // By working in bytes, we deal with mult-byte codepoints. 
+        // By working in bytes, we deal with mult-byte codepoints.
         byte[] strBytes = StrUtils.asUTF8bytes(str);
         final int N = strBytes.length;
         // Max length
@@ -224,13 +232,13 @@
         String s = new String(bytes, 0, i, StandardCharsets.UTF_8);
         return s;
     }
-    
+
     // Same but working on the string.  This is the pair of the encoder.
     // Encode/decode is normally use is for characters that illegal in a position
     // (e.g. URI components, spaces in URIs).
-    
-    // This string version is brittle - reverses the encoding of encodeHex() 
-    // but not general use as a decoder of a string. 
+
+    // This string version is brittle - reverses the encoding of encodeHex()
+    // but not general use as a decoder of a string.
     // Multi-byte codepoints do not get recombined if operating on strings/characters.
     private /*public*/ static String _forInfo_decodeHex(String str, char marker) {
         int idx = str.indexOf(marker);
@@ -267,7 +275,7 @@
             return ch - 'A' + 10;
         if ( ch >= 'a' && ch <= 'f' )
             return ch - 'a' + 10;
-        throw new AtlasException(format("Decoding error: bad character for hex digit (0x%02X) '%c' ",ch, ch)); 
+        throw new AtlasException(format("Decoding error: bad character for hex digit (0x%02X) '%c' ",ch, ch));
     }
 
     public static String escapeString(String x) {
diff --git a/jena-base/src/test/java/org/apache/jena/atlas/lib/TestStrUtils.java b/jena-base/src/test/java/org/apache/jena/atlas/lib/TestStrUtils.java
index 1628866..41dd980 100644
--- a/jena-base/src/test/java/org/apache/jena/atlas/lib/TestStrUtils.java
+++ b/jena-base/src/test/java/org/apache/jena/atlas/lib/TestStrUtils.java
@@ -19,6 +19,8 @@
 package org.apache.jena.atlas.lib;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
 
 import org.apache.jena.atlas.AtlasException;
 import org.junit.Test ;
@@ -26,8 +28,8 @@
 public class TestStrUtils
 {
     static char marker = '_' ;
-    static char esc[] = { ' ' , '_' } ; 
-    
+    static char esc[] = { ' ' , '_' } ;
+
     static void test(String x) {
         test(x, null);
     }
@@ -45,43 +47,72 @@
         String x2 = StrUtils.decodeHex(input, marker);
         assertEquals(expected, x2);
     }
-    
-    @Test public void enc01() { test("abc") ; } 
 
-    @Test public void enc02() { test("") ; } 
+    @Test public void enc01() { test("abc") ; }
 
-    @Test public void enc03() { test("_", "_5F" ) ; } 
-    
-    @Test public void enc04() { test(" ", "_20" ) ; } 
-    
-    @Test public void enc05() { test("_ _", "_5F_20_5F" ) ; } 
-    
-    @Test public void enc06() { test("_5F", "_5F5F" ) ; } 
-    
+    @Test public void enc02() { test("") ; }
+
+    @Test public void enc03() { test("_", "_5F" ) ; }
+
+    @Test public void enc04() { test(" ", "_20" ) ; }
+
+    @Test public void enc05() { test("_ _", "_5F_20_5F" ) ; }
+
+    @Test public void enc06() { test("_5F", "_5F5F" ) ; }
+
     @Test public void enc07() { test("_2") ; }
-    
-    @Test public void enc08() { test("AB_CD", "AB_5FCD") ; } 
-    
-    // JENA-1890: Multibyte characters before the "_"  
+
+    @Test public void enc08() { test("AB_CD", "AB_5FCD") ; }
+
+    // JENA-1890: Multibyte characters before the "_"
     // 사용_설명서 (Korean: "User's Guide")
-    
+
     @Test public void enc09() { test("\uC0AC\uC6A9_\uC124\uBA85\uC11C"); }
-    // Same string, but using the glyphs for the codepoints, not the \ u value. Same string after Java parsing. 
+    // Same string, but using the glyphs for the codepoints, not the \ u value. Same string after Java parsing.
     @Test public void enc09a() { test("사용_설명서"); }
-    
+
     // The decode code works more generally than the encoder.
     // This tests the decode of the UTF=-8 byte encoding of 사용_설명서
-    // Note "_5F" which is "_" encoded.  
+    // Note "_5F" which is "_" encoded.
     @Test public void enc10() { testDecode("_EC_82_AC_EC_9A_A9_5F_EC_84_A4_EB_AA_85_EC_84_9C", "사용_설명서"); }
-    
+
     @Test public void enc11() { testDecode("_41", "A"); }
-    
+
     @Test(expected=AtlasException.class) public void enc20() { testDecode("_4", null); }
 
     @Test(expected=AtlasException.class) public void enc21() { testDecode("_", null); }
-    
+
     @Test(expected=AtlasException.class) public void enc22() { testDecode("_X1", null); }
-    
+
     @Test(expected=AtlasException.class) public void enc23() { testDecode("_1X", null); }
 
+    @Test public void prefix_ignorecase_1() {
+        boolean b = StrUtils.strStartsWithIgnoreCase("foobar", "FOO");
+        assertTrue(b);
+    }
+
+    @Test public void prefix_ignorecase_2() {
+        boolean b = StrUtils.strStartsWithIgnoreCase("foobar", "bar");
+        assertFalse(b);
+    }
+    @Test public void prefix_ignorecase_3() {
+        boolean b = StrUtils.strStartsWithIgnoreCase("foo", "foobar");
+        assertFalse(b);
+    }
+
+    @Test public void suffix_ignorecase_1() {
+        boolean b = StrUtils.strEndsWithIgnoreCase("foobar", "BAR");
+        assertTrue(b);
+    }
+
+    @Test public void suffix_ignorecase_2() {
+        boolean b = StrUtils.strEndsWithIgnoreCase("foobar", "oo");
+        assertFalse(b);
+    }
+    @Test public void suffix_ignorecase_3() {
+        boolean b = StrUtils.strEndsWithIgnoreCase("bar", "foobar");
+        assertFalse(b);
+    }
+
+
 }
diff --git a/jena-core/src/main/java/org/apache/jena/irix/IRIProviderJenaIRI.java b/jena-core/src/main/java/org/apache/jena/irix/IRIProviderJenaIRI.java
index bf2fcf9..4b96884 100644
--- a/jena-core/src/main/java/org/apache/jena/irix/IRIProviderJenaIRI.java
+++ b/jena-core/src/main/java/org/apache/jena/irix/IRIProviderJenaIRI.java
@@ -76,16 +76,14 @@
         @Override
         public IRIx resolve(String other) {
             IRI iri2 = jenaIRI.resolve(other);
-            IRIProviderJenaIRI.exceptions(iri2);
-            return new IRIxJena(iri2.toString(), iri2);
+            return newIRIxJena(iri2);
         }
 
         @Override
         public IRIx resolve(IRIx other) {
             IRIxJena iriOther = (IRIxJena)other;
             IRI iri2 = jenaIRI.resolve(iriOther.jenaIRI);
-            IRIProviderJenaIRI.exceptions(iri2);
-            return new IRIxJena(iri2.toString(), iri2);
+            return newIRIxJena(iri2);
         }
 
         @Override
@@ -104,8 +102,7 @@
             IRI iri2 = jenaIRI.relativize(iriOther.jenaIRI, relFlags);
             if ( iri2.equals(iriOther.jenaIRI))
                 return null;
-            IRIProviderJenaIRI.exceptions(iri2);
-            return new IRIxJena(iri2.toString(), iri2);
+            return newIRIxJena(iri2);
         }
 
         @Override
@@ -131,25 +128,27 @@
         }
     }
 
+    private static IRIxJena newIRIxJena(IRI iri2) {
+        String iriStr2 = iri2.toString();
+        return newIRIxJena(iri2, iriStr2);
+    }
+
+    private static IRIxJena newIRIxJena(IRI iri2, String iriStr2) {
+        IRIProviderJenaIRI.exceptions(iri2, iriStr2);
+        return new IRIxJena(iriStr2, iri2);
+    }
+
     @Override
     public IRIx create(String iriStr) throws IRIException {
         // "create" - does not throw exceptions
         IRI iriObj = iriFactory().create(iriStr);
-        // errors and warnings.
-        if ( STRICT_FILE && isFILE(iriObj) ) {
-            if ( iriStr.startsWith("file://" ) && ! iriStr.startsWith("file:///") )
-                throw new IRIException("file: URLs should start file:///");
-        }
-        if ( isUUID(iriObj) )
-            checkUUID(iriObj, iriStr);
-        exceptions(iriObj);
-        return new IRIProviderJenaIRI.IRIxJena(iriStr, iriObj);
+        return newIRIxJena(iriObj, iriStr);
     }
 
     @Override
     public void check(String iriStr) throws IRIException {
         IRI iri = iriFactory().create(iriStr);
-        exceptions(iri);
+        exceptions(iri, iriStr);
     }
 
     @Override
@@ -205,7 +204,21 @@
     // Should be "false" in a release - this is an assist for development checking.
     private static final boolean includeWarnings = false;
 
-    private static IRI exceptions(IRI iri) {
+    private static IRI exceptions(IRI iri, String iriStr) {
+        if ( iriStr == null )
+            iriStr = iri.toString();
+
+        // Additional checks
+
+        // errors and warnings.
+        if ( STRICT_FILE && isFILE(iri) ) {
+            if ( iriStr.startsWith("file://" ) && ! iriStr.startsWith("file:///") )
+                throw new IRIException("file: URLs should start file:///: <"+iriStr+">");
+        }
+
+        if ( isUUID(iri, iriStr) ) {
+            checkUUID(iri, iriStr);
+        }
         if (!showExceptions)
             return iri;
         if (!iri.hasViolation(includeWarnings))
@@ -218,6 +231,7 @@
             int code = v.getViolationCode() ;
             // Filter codes.
             // Global settings below; this section is for conditional filtering.
+            // See also Checker.iriViolations for WARN filtering.
             switch(code) {
                 case Violation.PROHIBITED_COMPONENT_PRESENT:
                     // Allow "u:p@" when non-strict.
@@ -237,7 +251,7 @@
                     if ( isFILE(iri) )
                         continue;
             }
-            // First error.
+            // Signal first error.
             String msg = v.getShortMessage();
             throw new IRIException(msg);
         }
@@ -246,23 +260,22 @@
 
     // HTTP and HTTPS
     private static boolean isHTTP(IRI iri) {
-        return "http".equalsIgnoreCase(iri.getScheme()) || "https".equalsIgnoreCase(iri.getScheme());
+        return "http".equalsIgnoreCase(iri.getScheme())
+            || "https".equalsIgnoreCase(iri.getScheme());
     }
 
     private static boolean isURN(IRI iri)  { return "urn".equalsIgnoreCase(iri.getScheme()); }
     private static boolean isFILE(IRI iri) { return "file".equalsIgnoreCase(iri.getScheme()); }
 
-    // Checks trailing part of URI.
-    // Works on "urn:" and "urn:uuid:".
-    private static Pattern UUID_PATTERN = Pattern.compile(":[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$");
+    private static String UUID_REGEXP = "^(?:urn:uuid|uuid):[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$";
+    private static Pattern UUID_PATTERN = Pattern.compile(UUID_REGEXP, Pattern.CASE_INSENSITIVE);
 
-    private boolean isUUID(IRI iri) {
-        if ( "uuid".equalsIgnoreCase(iri.getScheme()) )
-                return true;
-        return iri.getRawPath().startsWith("uuid:");
+    private static boolean isUUID(IRI iri, String iriStr) {
+        return iriStr.regionMatches(true, 0, "urn:uuid:", 0, "urn:uuid:".length())
+            || iriStr.regionMatches(true, 0, "uuid:", 0, "uuid:".length());
     }
 
-    private void checkUUID(IRI iriObj, String original) {
+    private static void checkUUID(IRI iriObj, String original) {
         if ( iriObj.getRawFragment() != null )
             throw new IRIException("Fragment used with UUID");
         if ( iriObj.getRawQuery() != null )
diff --git a/jena-core/src/main/java/org/apache/jena/irix/IRIs.java b/jena-core/src/main/java/org/apache/jena/irix/IRIs.java
index 1efba86..c537056 100644
--- a/jena-core/src/main/java/org/apache/jena/irix/IRIs.java
+++ b/jena-core/src/main/java/org/apache/jena/irix/IRIs.java
@@ -39,7 +39,7 @@
         Objects.requireNonNull(iriStr);
         IRIx iri = IRIx.create(iriStr);
         if ( ! iri.isReference() )
-            throw new IRIException("Not an RDF IRI: "+iriStr);
+            throw new IRIException("Not an RDF IRI: <"+iriStr+">");
         return iri;
     }
 
diff --git a/jena-core/src/main/java/org/apache/jena/irix/IRIxResolver.java b/jena-core/src/main/java/org/apache/jena/irix/IRIxResolver.java
index 1132e0c..e557df4 100644
--- a/jena-core/src/main/java/org/apache/jena/irix/IRIxResolver.java
+++ b/jena-core/src/main/java/org/apache/jena/irix/IRIxResolver.java
@@ -19,6 +19,7 @@
 package org.apache.jena.irix;
 
 import java.util.Objects;
+import java.util.Optional;
 
 import org.apache.jena.atlas.lib.Cache;
 import org.apache.jena.atlas.lib.CacheFactory;
@@ -85,10 +86,8 @@
         IRIx x = (base != null && resolve)
                 ? base.resolve(str)
                 : IRIx.create(str);
-        if ( ! allowRelative ) {
-            if ( ! x.isReference() )
-                throw new IRIException("Not an RDF IRI: "+str);
-        }
+        if ( ! allowRelative && x.isRelative() )
+            throw new RelativeIRIException("Relative IRI: <"+str+">");
         return x;
     }
 
@@ -104,15 +103,13 @@
 
    public static Builder create() { return new Builder(); }
 
-
    /**
     * Create a {@link IRIxResolver} with the base URI which is resolved against the
     * current system default base.
     */
    public static Builder create(IRIxResolver original) {
        Builder builder = new Builder();
-       builder.base = original.base;
-       builder.baseSet = true;
+       builder.base = Optional.ofNullable(original.base);
        builder.resolve = original.resolve;
        builder.allowRelative = original.allowRelative;
        return builder;
@@ -136,29 +133,26 @@
    }
 
    public static class Builder {
-
-       private boolean baseSet = false;
-       private IRIx base = null;
-       private boolean resolve = true;
+       // null is "unset".
+       private Optional<IRIx> base   = null;
+       private boolean resolve       = true;
        private boolean allowRelative = true;
 
        private Builder() {}
 
        public Builder base(IRIx baseURI) {
-           this.base = baseURI;
-           this.baseSet = true;
+           this.base = Optional.ofNullable(baseURI);
            return this;
        }
 
        public Builder base(String baseStr) {
-           base = (baseStr == null) ? null : IRIs.resolveIRI(baseStr);
-           this.baseSet = true;
+           IRIx baseIRI = (baseStr == null) ? null : IRIs.resolveIRI(baseStr);
+           this.base = Optional.ofNullable(baseIRI);
            return this;
        }
 
        public Builder noBase() {
-           base = null;
-           this.baseSet = true;
+           this.base = Optional.empty();
            return this;
        }
 
@@ -173,9 +167,10 @@
        }
 
        public IRIxResolver build() {
-           if ( ! baseSet )
+           if ( base == null )
                throw new IRIException("Base has not been set");
-           return new IRIxResolver(base, resolve, allowRelative);
+           IRIx baseIRI = base.orElse(null);
+           return new IRIxResolver(baseIRI, resolve, allowRelative);
        }
    }
 }
diff --git a/jena-core/src/main/java/org/apache/jena/irix/RelativeIRIException.java b/jena-core/src/main/java/org/apache/jena/irix/RelativeIRIException.java
new file mode 100644
index 0000000..ea08fd4
--- /dev/null
+++ b/jena-core/src/main/java/org/apache/jena/irix/RelativeIRIException.java
@@ -0,0 +1,28 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.jena.irix;
+
+/**
+ * Exception thrown due to relative IRIs when no permitted.
+ * See {@link IRIxResolver#resolve}.
+ */
+public class RelativeIRIException extends IRIException {
+    public RelativeIRIException(String msg) { super(msg); }
+    @Override public Throwable fillInStackTrace() { return this ; }
+}
diff --git a/jena-core/src/main/java/org/apache/jena/irix/SetupJenaIRI.java b/jena-core/src/main/java/org/apache/jena/irix/SetupJenaIRI.java
index 3497e51..301bd4e 100644
--- a/jena-core/src/main/java/org/apache/jena/irix/SetupJenaIRI.java
+++ b/jena-core/src/main/java/org/apache/jena/irix/SetupJenaIRI.java
@@ -65,6 +65,9 @@
 
     /** IRI Factory with "checker" settings. */
     /*package*/ static final IRIFactory setupCheckerIRIFactory() {
+        // See IRIProviderJenaIRI.exceptions for context specific tuning.
+        // See Checker.iriViolations for filtering and output from parsers.
+
         IRIFactory iriCheckerFactory = new IRIFactory();
 
         //iriCheckerInst.shouldViolation(false,true);
@@ -81,6 +84,9 @@
 
         // -- Scheme specific rules.
         setErrorWarning(iriCheckerFactory, ViolationCodes.SCHEME_PATTERN_MATCH_FAILED, false, true);
+        // jena-iri produces an error for PROHIBITED_COMPONENT_PRESENT regardless.
+        // See Checker.iriViolations for handling this
+        //setErrorWarning(iriCheckerFactory, ViolationCodes.PROHIBITED_COMPONENT_PRESENT, false, true);
 
         // == Scheme
         setErrorWarning(iriCheckerFactory, ViolationCodes.UNREGISTERED_IANA_SCHEME, false, false);
diff --git a/jena-core/src/test/java/org/apache/jena/irix/TestIRIx.java b/jena-core/src/test/java/org/apache/jena/irix/TestIRIx.java
index fae9c44..49f7b5c 100644
--- a/jena-core/src/test/java/org/apache/jena/irix/TestIRIx.java
+++ b/jena-core/src/test/java/org/apache/jena/irix/TestIRIx.java
@@ -21,6 +21,8 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 
+import java.util.Locale;
+
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.Parameterized;
@@ -84,6 +86,23 @@
 
     @Test public void urn_05()  { notStrict("urn", ()->parse("urn:ex:")); }
 
+    private static String testUUID = "aa045fc2-a781-11eb-9041-afa3877612ee";
+
+    @Test public void uuid_01() { parse("uuid:"+testUUID); }
+
+    @Test public void uuid_02() { parse("uuid:"+(testUUID.toUpperCase(Locale.ROOT))); }
+
+    @Test public void uuid_03() { parse("UUID:"+testUUID); }
+
+    @Test public void uuid_04() { parse("urn:uuid:"+testUUID); }
+
+    @Test public void uuid_05() { parse("urn:uuid:"+(testUUID.toUpperCase(Locale.ROOT))); }
+
+    @Test public void uuid_06() { parse("URN:UUID:"+testUUID); }
+
+    @Test(expected=IRIException.class)
+    public void uuid_07() { parse("urn:uuid:06e775ac-ZZZZ-11b2-801c-8086f2cc00c9"); }
+
     // -- Compliance with file scheme: https://tools.ietf.org/html/rfc8089
 
     @Test public void file_01() { parse("file:///path/name"); }
diff --git a/jena-core/src/test/java/org/apache/jena/irix/TestResolve.java b/jena-core/src/test/java/org/apache/jena/irix/TestResolve.java
index 63625d6..cdf670a 100644
--- a/jena-core/src/test/java/org/apache/jena/irix/TestResolve.java
+++ b/jena-core/src/test/java/org/apache/jena/irix/TestResolve.java
@@ -196,6 +196,12 @@
         testResolve("http://example/dir1/dir2/", "//EX/OtherPath", "http://EX/OtherPath");
     }
 
+    @Test
+    public void resolve_34() {
+        String uuid = "urn:uuid:e79b5752-a82e-11eb-8c4e-cba73c34870a";
+        testResolve("http://example/base#", uuid, uuid);
+    }
+
     private void testResolve(String base, String rel, String expected) {
         IRIx baseIRI = IRIx.create(base);
         IRIx relIRI = IRIx.create(rel);
diff --git a/jena-db/jena-tdb2/src/main/java/org/apache/jena/tdb2/sys/DatabaseOps.java b/jena-db/jena-tdb2/src/main/java/org/apache/jena/tdb2/sys/DatabaseOps.java
index 4745d10..7a5beb9 100644
--- a/jena-db/jena-tdb2/src/main/java/org/apache/jena/tdb2/sys/DatabaseOps.java
+++ b/jena-db/jena-tdb2/src/main/java/org/apache/jena/tdb2/sys/DatabaseOps.java
@@ -182,7 +182,7 @@
 
             // Is this the same database location?
             if ( ! loc1.equals(loc1a) )
-                throw new TDBException("Inconsistent (not latested?) : "+loc1a+" : "+loc1);
+                throw new TDBException("Inconsistent (not latest?) : "+loc1a+" : "+loc1);
             // -- Checks
 
             // Version
diff --git a/jena-db/jena-tdb2/src/test/java/org/apache/jena/tdb2/sys/TestDatabaseOps.java b/jena-db/jena-tdb2/src/test/java/org/apache/jena/tdb2/sys/TestDatabaseOps.java
index 7584d0f..cfbf730 100644
--- a/jena-db/jena-tdb2/src/test/java/org/apache/jena/tdb2/sys/TestDatabaseOps.java
+++ b/jena-db/jena-tdb2/src/test/java/org/apache/jena/tdb2/sys/TestDatabaseOps.java
@@ -162,6 +162,7 @@
         });
 
         DatasetGraphSwitchable dsgs = (DatasetGraphSwitchable)dsg;
+        assertNotNull("DatasetGraphSwitchable created", dsgs.getLocation());
         DatasetGraph dsg1 = dsgs.get();
         Location loc1 = ((DatasetGraphTDB)dsg1).getLocation();
 
diff --git a/jena-fuseki2/jena-fuseki-webapp/src/test/resources/log4j2.properties b/jena-fuseki2/jena-fuseki-webapp/src/test/resources/log4j2.properties
index 41cfb2d..7538a8c 100644
--- a/jena-fuseki2/jena-fuseki-webapp/src/test/resources/log4j2.properties
+++ b/jena-fuseki2/jena-fuseki-webapp/src/test/resources/log4j2.properties
@@ -41,6 +41,9 @@
 logger.fuseki-admin.name  = org.apache.jena.fuseki.Admin
 logger.fuseki-admin.level = WARN
 
+logger.fuseki-config.name  = org.apache.jena.fuseki.Config
+logger.fuseki-config.level = WARN
+
 logger.jetty.name  = org.eclipse.jetty
 logger.jetty.level = WARN