[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: XSLT 2.0 / XPath 2.0 - Assumptions
At 12:02 PM 5/12/2002 -0400, Mike Champion wrote: >"One of the great strengths of XML is its flexibility in representing >many different kinds of information from diverse sources. To exploit >this flexibility, an XML query language must provide features for >retrieving and interpreting information from these diverse sources." > >"It is designed to be a small, easily implementable language in which >queries are concise and easily understood. It is also flexible enough >to query a broad spectrum of XML information sources, including both >databases and documents. ... XQuery is derived from an XML query >language called Quilt [Quilt], which in turn borrowed features from >several other languages, including XPath 1.0 [XPath 1.0], XQL [XQL], >XML-QL [XML-QL], SQL [SQL], and OQL [ODMG]." > >Maybe "unification of approaches" is too strong, but clearly the >objective is to query XML views of data irrespective of whether the >physical data are in documents, SQL databases, OO repositories, or >native XML databases. Yes, very much so. > > I must say that if that is indeed > > the goal, then it is doomed to failure. RDBMS, OO, and XML are three > > very different models and I don't think you can usefully combine > > them. > >Well, XML is a universal data meta-format; you can represent SQL, OO, >and documentL data in XML, and XQuery lets you query that >representation. >I didn't mean to imply that XQuery would let you unify the underlying >data models. It's true that you lose some of the relational model in >an XML representation (the order of "rows" and "columns" becomes >significant, and duplicates become allowed all of a sudden, and XQuery >has to bend over backwards to allow these XML-isms to be ignored, as >best I understand it). Right. XQuery does not use the SQL model or the OO model, it relies solely on the XPath data model. Many aspects of the original sources are lost. >I personally find this the most appealing aspect of XQuery -- I *want* >to be able to do a join across an XML document collection and a table >in an RDBMS, and maybe some topic map or RDF metadata thrown in for >good measure. This is one of the main reasons for XQuery, IMHO. Jonathan
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