[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Content roles in XML
I'm very new to XML, and in developing a DTD for JAR files, JavaBeans, and Rational Rose petal files, I experienced a recurring problem. The EventSet element of the JavaBeans DTD is exemplary. Here's a fragment of the JavaBeans DTD I came up with: <!ELEMENT EventSet (Annotation*, Method, Method, Method+)> <!ATTLIST EventSet %FeatureDescriptor; listenerType CDATA #REQUIRED isInDefaultEventSet (true | false) "false" isUnicast (true | false) "false" > The content of an Event set includes two required methods, and a collection of other methods. In the DTD, there's no way that I know of to indicate the roles these methods play in the EventSet. I would like to say something like: <!ELEMENT EventSet (Annotation*, addListenerMethod, removeListenerMethod, eventMethod+)> <!ATTLIST EventSet %FeatureDescriptor; listenerType CDATA #REQUIRED isInDefaultEventSet (true | false) "false" isUnicast (true | false) "false" > where addListenerMethod, removeListenerMethod, and eventMethod are all Method elements. This more clearly describes the content of an EventSet and avoids using positioning only to capture the meaning of element content. I could use parameter entities to achieve this effect as in: <!ENTITY % addListenerMethod "Method"> <!ENTITY % removeListenerMethod "Method"> <!ENTITY % eventMethod "Method"> <!ELEMENT EventSet (Annotation*, %addListenerMethod;, %removeListenerMethod;, %eventMethod;+)> <!ATTLIST EventSet %FeatureDescriptor; listenerType CDATA #REQUIRED isInDefaultEventSet (true | false) "false" isUnicast (true | false) "false" > Is this reasonable? Good XML DTD style? Not too much of a runtime overhead? A common practice? Note that this probably wouldn't help with the parsed XML as there would be a Method element for each method. You couldn't ask an EntitySet element for it's addListenerMethod content like you could ask it for it's isUnicast attribute. You'd have to know to get the first Method in the content. Of course an extensible parser with factory methods for constructing parse tree nodes could hide the position dependence and provide more meaningful accessors. I guess what I'm looking for is a way to capture (using UML terms) the association roles between the EventSet Class and the Method Class. There are 3 associations between these two classes, and I need a way to distinguish them. Anyone have any other ideas? Has anyone else experienced this situation? 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...)
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