[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Frontier as a scalable XML repository (was Re: Is XML dead already o
On Sat, 30 Jan 1999, David Megginson wrote: > I said that there is not a good, scalable XML repository available > right now. I have been involved in several attempts to build SGML or XML storage systems using databases. Performance is always a big issue. With an rdbms you have the interesting notion that the database understands neither sequence nor containment directly. You also have a difficulty with text retrieval, especially if you need it to span element <kw>boundaries</kw> and find "element boundaries" twice in this paragraph, yet still treat the "kw" element as a separately indexed object. On the other hand, the relational database vendors have worked very hard at peformance, and you get lots of benefits built in, such as journalling, rollback, backup, standard texts on SQL... the whole bit. Object oriented databases *do* understand sequence and containment, and understand it very well. But they don't have a standard query language. OQL is not implemented very evenly yet, and when it is, it has restrictions. We (at Groveware) found it difficult to represent a query such as find an elementNode with .name = "P" containing a childList containing an object of type elementNode with 'name' = "kw" containing a childList containing an object of type cdata where strcmp(content, "boundaries") == 0 both in OQL and in Object Design's non-OQL query language. One would like to say find <p> containing <kw> containing "boundaries" and have that be efficient, and that's a real challenge. The OLAP people and the text retrieval people are probably best placed to handle large quantities of XML, if the text retrieval people can manage to swallow the word "dynamic" and the OLAP people can get a grip on text retrieval :-) Speaking of which, I am working on my C/Unix text retrieval package (lq-text) again, hoping to add some XML support soon. But I digress. If you haven't seen an OODB system that scaled well, it may be (I am speculating) that the generic systems are too slow because query optimisation is still too hard; the application-specific ones are less visible, and probably perform very well. Lee -- SGML/XML consulatant, Toronto, Canada -- liamquin at interlog.com -- http://www.interlog.com/~liamquin/ also Director of Development, Groveware Inc, http://www.groveware.com/~lee/ 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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