[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: Primary and Foreign Keys
Or link. Depends on the processing. In one document, you can handle compounds using IDREFS but no, you can't assume uniqueness so blarg. Nesting makes sense for child tables. My guess is for the particular system I am looking at though, it will need to be broken into multiple documents. 200+ tables, over 5200 fields, different configurations, the works. Then there are issues of whether one is designing the schema for one system or as a potential standard data description for different systems. One can't assume the design is for the internet per se. Many field systems run in an occasionally connected mode. In some respects, file management works ok because that is simple to encrypt and ftp works as long as the port is available. You can't assume the data will be transferred and destroyed. Some kinds of systems demand copies of transferred files for traceability. Len http://www.mp3.com/LenBullard Ekam sat.h, Vipraah bahudhaa vadanti. Daamyata. Datta. Dayadhvam.h -----Original Message----- From: Ronald Bourret [mailto:rpbourret@r...] Sent: Wednesday, July 25, 2001 1:18 PM To: xml-dev Subject: Re: Primary and Foreign Keys "Thomas B. Passin" wrote: > > [Ronald Bourret] > > > > > 6) Leave the key value out of the XML document. This requires that > > nesting is used to indicate key relationships and makes sense when: (a) > > key values are generated by the database, and (b) the data is being > > transferred to a different database. Such values not guaranteed to be > > unique in the second database. > > > > I almost included this thought in my post, but didn't because it occurred to > me that even if you nested a child entity within a parent, you might still > need to refer to it from somewhere else rather than duplicate its data. True. The decision of whether to duplicate the data probably depends on how you are processing the document. With SAX, it's easier to process duplicate data, since it reduces caching. It also depends on what role the document plays. If it's a simple data transfer -- the document will be created once, read, and destroyed -- duplicate data probably isn't that dangerous. If the document will be around for a while -- especially if it can be updated -- duplicate data raises the possibility of introducing inconsistencies. > So > it seemed that eliminating the ID and nesting could be orthogonal. A > case-by-case decision, methinks. Semi-orthogonal. If you eliminate the ID, you have to nest in order to show the relationship (unless I'm missing something). If you nest, you don't have to eliminate the ID.
|
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
|