Index: trunk/src/org/openstreetmap/josm/io/OsmReader.java
===================================================================
--- trunk/src/org/openstreetmap/josm/io/OsmReader.java	(revision 15469)
+++ trunk/src/org/openstreetmap/josm/io/OsmReader.java	(revision 15470)
@@ -7,4 +7,6 @@
 import java.util.Collection;
 import java.util.Objects;
+import java.util.Set;
+import java.util.TreeSet;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -40,4 +42,21 @@
     protected XMLStreamReader parser;
 
+    protected boolean convertUnknownToTags;
+
+    private static final Set<String> COMMON_XML_ATTRIBUTES = new TreeSet<>();
+
+    static {
+        COMMON_XML_ATTRIBUTES.add("id");
+        COMMON_XML_ATTRIBUTES.add("timestamp");
+        COMMON_XML_ATTRIBUTES.add("user");
+        COMMON_XML_ATTRIBUTES.add("uid");
+        COMMON_XML_ATTRIBUTES.add("visible");
+        COMMON_XML_ATTRIBUTES.add("version");
+        COMMON_XML_ATTRIBUTES.add("action");
+        COMMON_XML_ATTRIBUTES.add("changeset");
+        COMMON_XML_ATTRIBUTES.add("lat");
+        COMMON_XML_ATTRIBUTES.add("lon");
+    }
+
     /**
      * constructor (for private and subclasses use only)
@@ -46,5 +65,17 @@
      */
     protected OsmReader() {
+        this(false);
+    }
+
+    /**
+     * constructor (for private and subclasses use only)
+     * @param convertUnknownToTags if true, keep unknown xml attributes as tags
+     *
+     * @see #parseDataSet(InputStream, ProgressMonitor)
+     * @since 15470
+     */
+    protected OsmReader(boolean convertUnknownToTags) {
         // Restricts visibility
+        this.convertUnknownToTags = convertUnknownToTags;
     }
 
@@ -394,4 +425,12 @@
             parseAction(current, parser.getAttributeValue(null, "action"));
             parseChangeset(current, parser.getAttributeValue(null, "changeset"));
+
+            if (convertUnknownToTags) {
+                for (int i = 0; i < parser.getAttributeCount(); i++) {
+                    if (!COMMON_XML_ATTRIBUTES.contains(parser.getAttributeLocalName(i))) {
+                        parseTag(current, parser.getAttributeLocalName(i), parser.getAttributeValue(i));
+                    }
+                }
+            }
         } catch (UncheckedParseException | XMLStreamException e) {
             throw new IllegalDataException(e);
@@ -458,5 +497,22 @@
      */
     public static DataSet parseDataSet(InputStream source, ProgressMonitor progressMonitor) throws IllegalDataException {
-        return new OsmReader().doParseDataSet(source, progressMonitor);
+        return parseDataSet(source, progressMonitor, false);
+    }
+
+    /**
+     * Parse the given input source and return the dataset.
+     *
+     * @param source the source input stream. Must not be null.
+     * @param progressMonitor the progress monitor. If null, {@link NullProgressMonitor#INSTANCE} is assumed
+     * @param convertUnknownToTags true if unknown xml attributes should be kept as tags
+     *
+     * @return the dataset with the parsed data
+     * @throws IllegalDataException if an error was found while parsing the data from the source
+     * @throws IllegalArgumentException if source is null
+     * @since 15470
+     */
+    public static DataSet parseDataSet(InputStream source, ProgressMonitor progressMonitor, boolean convertUnknownToTags)
+            throws IllegalDataException {
+        return new OsmReader(convertUnknownToTags).doParseDataSet(source, progressMonitor);
     }
 }