[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: What should TrAX look like? (Was: Re: Articleon
Kevin Jones wrote: > The core issue for me here is that the processing software > needs to have a way of determining the capability of the > data model it is being asked to use so that it can adapt > its evaluation strategy according to those capabilities. > Without this we are forever stuck with having to use known > matched pairs of processing software and data model. I think that's a bit overly complex and puts the responsibility in the wrong place. The engine should not have to adapt itself to the capabilities of different models. I suspect it would be much cleaner to take an approach like Jaxen's. In this approach there's a core set of basic operations that all model-connectors must implement (getChild, getAttribute, getParent, etc.). However most other axes have default implementations that build on top of the basic operations. For instance, the ancestor axis is easily implemented on top of getParent. Thus a minimal implementation only has to provide about 20 fairly straight-forward operations. However, if the implementation does have more efficient ways to implement the ancestor axis than just walking up the parent axis, it can override the default getAncestor implementation with a more customized version. Ditto for the other axes. The engines never need to know the details. This seems a lot more flexible to me and much more likely to be implemented than having the engines query the models for their capabilities and then adjust their algorithms accordingly. -- Elliotte Rusty Harold elharo@m... XML in a Nutshell 3rd Edition Just Published! http://www.cafeconleche.org/books/xian3/ http://www.amazon.com/exec/obidos/ISBN=0596007647/cafeaulaitA/ref=nosim
|
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
|