Say I have this XML

<doc:document>
  <objects>
    <circle radius="10" doc:colour="red" />
    <circle radius="20" doc:colour="blue" />
  </objects>
</doc:document>

And this is how it is parsed (pseudo code):

// class DocumentParser
public Document parse(Element edoc) {
     doc = new Document();
     doc.objects = ObjectsParser.parse(edoc.getChild("objects"));

     for ( ...?... ) {
         doc.objectColours.put(object, colour);
     }

     return doc;
}

ObjectsParser is responsible for parsing the objects bit, but is not and should not be aware of the existence of documents. However, in Document colours are associated with objects by use of a Map.

What kind of pattern would you recommend to give the colour settings back to DocumentParser.parse from ObjectsParser.parse so it can associate it with the objects they belong to in a map?

The alternative would be something like this:

<doc:document>
  <objects>
    <circle id="1938" radius="10" />
    <circle id="6398" radius="20" />
  </objects>
  <doc:objectViewSettings>
   <doc:objectViewSetting object="1938" colour="red" />
   <doc:objectViewSetting object="6398" colour="blue" />
  </doc:objectViewSettings>
</doc:document>

Ugly!