[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Are Updates really needed in XQuery?
We have found many applications needing an update capability, but usually combined with the ability to find out if an update is needed, i.e. a comparison capability that is XML-aware. DeltaXML is based on this, i.e. finding changes to XML documents/data and representing these in XML. XML is extensively used for data, and most data changes. So to be able to find the changes intelligently and provide an update representation in XML is useful. The way we represent such updates means that they can be processed as normal XML, so we do not use XPath (partly because DeltaXML pre-dates XPath, but also because for extensive changes/updates across a large XML file Xpath is not the best way to represent it). XML file versioning is one application - the ability to store deltas to roll-forward or roll-back. If data sets are large, it makes no sense to store all the data each time. To be able to represent changes to XML data as XML opens up a whole set of new possibilities in XML applications, e.g. display/process changes to a data set. You can see how this works on our web site (http://www.deltaxml.com), but we are certainly finding many applications that need to provide an update capability! This does not mean that it should be part of the XQuery language, of course. Robin At 5:56 am -0800 29/1/02, Brian Vickery wrote: >I have a simple question, "Why do we need updates as part of the XQuery >language at all?" > >I have read the latest XQuery Update proposal (from the "XQuery Update >Proposal" by Patrick Lehti) and the older XUpdate WD. I come from a >database background and view updates as imperative to the XQuery/XPath >language, but can't state "why". I'm getting a lot of grief regarding >having Updates at all. The types of "inserts" and "deletes" typically shown >are just adding/deleting a document from a "collection" (if collections >existed and they should IMHO). > >Some examples are: > >1. If I have a collection of XML invoices why would I ever want to update >these? An invoice is written once and never changed! > >2. If I have a document centric collection of XML document I would most >likely version each document, thus why do we need updates? > >3. If I have all my business contacts (companies I do business with) stored >in an XML collection, why wouldn't I just do a complete replace if I wanted >to change a companies name or address? > >Does anyone have any real life scenarios/business cases that "MUST" have >updates? > >thanks, > > > >----------------------------------------------------------------- >The xml-dev list is sponsored by XML.org <http://www.xml.org>, an >initiative of OASIS <http://www.oasis-open.org> > >The list archives are at http://lists.xml.org/archives/xml-dev/ > >To subscribe or unsubscribe from this list use the subscription >manager: <http://lists.xml.org/ob/adm.pl> -- -- ----------------------------------------------------------------- Robin La Fontaine, Director, Monsell EDM Ltd DeltaXML: "Change control for XML in XML" Tel: +44 1684 592 144 Fax: +44 1684 594 504 Email: robin.lafontaine@d... http://www.deltaxml.com
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