lookupConfig

The <lookupConfig> element contains lookup element. Each <lookup> element specifies an attribute and a URI, which points to an HTML page that can generate a list of value from which the user can pick one.

<x:lookupConfig>
  <x:lookup 
    parentPattern="self::picture" 
    name="source"
    url="lookup/image/index.html" 
    forceLookup="true" 
    autoOpen="true"/>
  <x:lookup 
    parentPattern="self::a" 
    name="href"
    url="lookup/link/index.html" 
    forceLookup="false" 
    autoOpen="true"/>
</x:lookupConfig>

Note: It is not possible to create cross-domain lookups, as it is impossible for JavaScript from one domain to access windows or iframes therefore, on other domains.