[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: RE: XML indexing/search engine
8/23/2002 2:10:38 PM, "Bullard, Claude L (Len)" <clbullar@i...> wrote: >DOMs make fine semiotic storage models for a local >focus of attention. So does a relational view, but >keeping one of those around means keeping the rest >of the RDBMS handy, and that is expensive in several >dimensions. I would never voluntarily use the word "semiotic" in a sentence without quotes around it :~) but I think I agree. Data that will be re-used in unpredictable ways and updated by multiple applications really should be normalized and stored in an RDBMS to minimize redundancy, maintain referential integrity, preserve independence between the store and the application, and all the other things that Prof. Codd talks about. On the other hand, not all data one encounters imposes all these requirements on its processors, and XML is a convenient and useful way to capture and manipulate some snapshot of the data as "documents." Documents inside an application are conveniently manipulated as DOMs (generically speaking). If the documents are processed serially via a pipeline or workflow, then if often does make a lot of sense to have them manipulated as XML by each node in the sequence rather than going back to the master database(s). As Len notes, this can be very expensive, and the RDBMS is not always handy. The canonical example is an invoice, because real-world invoices (as I undertand it) generally normalize into about 20 RDBMS tables, and can span 100 or so tables in an industrial-strength ERP system (I'm told). In a serialized, distributed invoice processing system, it can be a lot more efficient to extract a snapshot of one logical invoice from these tables into XML, pass it around as a "document" to be read, annotated, updated, etc., and then put it back in the ERP system (or whatever) once the various humans have done whatever they have to do to process an invoice. A theme I keep coming back to in xml-dev rantings is that the WHOLE POINT of XML is to live at the nexus of human and machine systems. Extracting complex DBMS or ERP representations into ordinary business "documents" makes them more accessible to humans and human-oriented business processes (which were designed to be serialized, distributed, and capable of working with only one writer holding the "lock" at any given time.)
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