[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Schema constraint
Phil Ruelle wrote: > > Can anyone tell me if it's possible to write a constraint with XML > Schema to enforce that for an element with two child elements at > least one of them exists? (I thought this had been asked before but > couldn't find it in the archives) No you can't. The usual 3 solutions for this kind of issue apply: 1) Define a Schematron rule within a W3C XML Schema annotation. 2) Use another schema language. 3) Add a xsi:type attribute in your instance document to say in which case you are (element 1 or element 2 mandatory). > > On a related note, why would somene choose to use <group> > rather than a complex type? I can't help but think I've missed > something as groups seem to be a limited (must be global, no > attributes) version of complex types. They are less powerful in a sense since you don't specify attributes in an element group, OTH you can use several of them together within a single sequence or choice where you can't "join" several complex types. Hope this helps. Eric > TIA, > > Phil Ruelle > -- See you at XTech in San Diego. http://conferences.oreillynet.com/cs/os2001/view/e_spkr/790 ------------------------------------------------------------------------ Eric van der Vlist http://xmlfr.org http://dyomedea.com http://xsltunit.org http://4xt.org http://examplotron.org ------------------------------------------------------------------------
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