[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Do we need link-catalogs for schemas?
From: Peter Murray-Rust <peter@u...> >It stands for Generic Identifier and for practical purposes is (I think) >synonymous with Element Type Name in XML, i.e. <FOO> has a GI of "FOO". That's what I first thought. But then I began to wonder... >Question in return, what exactly is delegation and can you give an example. >[It's been mentioned both in the context of Java classes and link-catalogs]. I think it has to do with aggregation. A client of the aggregate requests a delegate of the aggregate which supports a particular interface. At least, this is what I've been assuming... This is the heart of COM and was to be a part of JavaBeans. It is also the key to advanced Coin applications, as the CoinsDocument class is part of an aggregate. It is important in Java, to get arround single-inheritence. I believe the problem with the JavaSoft aggregation was that the client specified a Class object, requiring that the tree of classes ('cause you must include interfaces) had to be searched for each object in the aggregate collection of objects. Coins uses a filter object to select the appropriate delegate. This means that (1) you can simply use the instanceof operator in the filter match method instead of having to do the class tree search and (2) you can select based on any criteria, allowing for selection based on role. (I need to make this package accessable again on the Coins web page. Its freeware.) Now since there is no standard api (for Java), its kinda hard to give a simple example, code wise. But lets say that we have a Juggler with two listener registration interfaces, one for start and one for stop. If the Juggler were a single class, you would simply cast the Juggler object to the appropriate interface. Unfortunately, that means that the two interfaces can not have any common methods. If the registration interfaces for start and stop were seperate objects, but were different interface types, then you could ask the Juggler aggregate object for, say, an instance of the startListenerRegistration object. If role were supported, then the objects supporting the ActionListenerRegistration interface could be requested as the "start" object or the "stop" object. Bill xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i... Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ To (un)subscribe, mailto:majordomo@i... the following message; (un)subscribe xml-dev To subscribe to the digests, mailto:majordomo@i... the following message; subscribe xml-dev-digest List coordinator, Henry Rzepa (mailto:rzepa@i...)
|
PURCHASE STYLUS STUDIO ONLINE TODAY!Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced! Download The World's Best XML IDE!Accelerate XML development with our award-winning XML IDE - Download a free trial today! Subscribe in XML format
|