diff --git a/README.md b/README.md
index 8dedb7fe075b38f75319141d76b17858b6b63f3b..a88d85b9c50d1d5be972ac67f5cd05fa72e3b886 100644
--- a/README.md
+++ b/README.md
@@ -40,6 +40,7 @@ Schemas
    <entry schematype="schema" namespace="http://www.loc.gov/standards/alto/ns-v2#" schemaurl="http://www.loc.gov/standards/alto/alto-v2.0.xsd" />
 </slubschemacatalog>
 ```
+* please ensure, that the 'schemaurl' starts  either with 'http://$server/', 'https://$server/' or 'file://localhost/'! For testing purposes relative URLs also supported. 
 
 For a (german) introduction how to use it, check https://www.data2type.de/xml-xslt-xslfo/docbook/xml-kataloge 
 
diff --git a/java/org/slub/rosetta/dps/repository/plugin/XmlFormatValidationPlugin.java b/java/org/slub/rosetta/dps/repository/plugin/XmlFormatValidationPlugin.java
index c2b2578754277100c30cbb2dbaad881ab82f94ec..6ce4580bc21dbc7dc818939e02db7a7436959eb3 100644
--- a/java/org/slub/rosetta/dps/repository/plugin/XmlFormatValidationPlugin.java
+++ b/java/org/slub/rosetta/dps/repository/plugin/XmlFormatValidationPlugin.java
@@ -92,35 +92,42 @@ public class XmlFormatValidationPlugin implements FormatValidationPlugin {
         }
     }
 
-    private void addtoNamespaceSchemaMap(String namespaceSchemaMapFile, String attr_type, String namespace, String sUri) throws URISyntaxException, SAXException {
-            var schematype = ValidationSchemaType.nothing;
-            switch (attr_type) {
-                case "schema" -> schematype = ValidationSchemaType.schema;
-                case "schematron" -> schematype = ValidationSchemaType.schematron;
-                case "relaxng" -> schematype = ValidationSchemaType.relaxng;
-                case "nonvalidating" -> schematype = ValidationSchemaType.nonvalidating;
-                default -> validationLogger.error("attribute schematype needs to be type of schema, schematron or relaxng, but is " + attr_type);
-            }
-            URI uri;
+    private void addtoNamespaceSchemaMap(String namespaceSchemaMapFile, String attr_type, String namespace, String sUrl) throws URISyntaxException, SAXException {
+        ValidationSchemaType schematype = ValidationSchemaType.nothing;
+        switch (attr_type) {
+            case "schema" -> schematype = ValidationSchemaType.schema;
+            case "schematron" -> schematype = ValidationSchemaType.schematron;
+            case "relaxng" -> schematype = ValidationSchemaType.relaxng;
+            case "nonvalidating" -> schematype = ValidationSchemaType.nonvalidating;
+            default ->
+                    validationLogger.error("attribute schematype needs to be type of schema, schematron or relaxng, but is " + attr_type);
+        }
+        if (
+                sUrl.startsWith("file:")
+            && !sUrl.startsWith("file://localhost/")
+        ) {
+            validationLogger.error("attribute schemaurl should be start with: 'http://$server/path', 'https://$server/path' or 'file://localhost/path' to ensure coorect working, got: " + sUrl);
+        }
+        URI uri;
         if (
-                (sUri.startsWith("http://"))
-                        || (sUri.startsWith("https://"))
-                        || (sUri.startsWith("file://"))
-                        || (sUri.contains("://"))
+                (sUrl.startsWith("http://"))
+                        || (sUrl.startsWith("https://"))
+                        || (sUrl.startsWith("file://"))
+                        || (sUrl.contains("://"))
         ) {
-            uri = new URI(sUri);
+            uri = new URI(sUrl);
         } else {
-            uri = remapUri(namespaceSchemaMapFile, sUri);
-            validationLogger.debug( "SCHEMACATALOG, remap to URI: " + uri);
+            uri = remapUri(namespaceSchemaMapFile, sUrl);
+            validationLogger.debug("SCHEMACATALOG, remap to URI: " + uri);
         }
         ValidationSchema v = new ValidationSchema(namespace, schematype, uri);
-            namespaceSchemaMap.add(v);
+        namespaceSchemaMap.add(v);
     }
 
     //@NotNull
-    private URI remapUri(String namespaceSchemaMapFile, String sUri) throws URISyntaxException {
-        URI partUri = new URI(sUri);
-        String baseStr = "file://" + new File(namespaceSchemaMapFile).getAbsoluteFile().getParent() + "/";
+    private URI remapUri(String namespaceSchemaMapFile, String sUrl) throws URISyntaxException {
+        URI partUri = new URI(sUrl);
+        String baseStr = "file://localhost/" + new File(namespaceSchemaMapFile).getAbsoluteFile().getParent() + "/";
         URI baseUri = new URI( baseStr);
         return baseUri.resolve(partUri);
     }