[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: modeling, validating and documenting an xml grammar
From: "Chiusano Joseph" <chiusano_joseph@b...> > <Quote> > What are the real-world use cases of minOccurs and maxOccurs? > In my experience, occurrence constraints specifying anything > other than zero, one, or many are almost always an indication > of a bad design decision somewhere in the system. > </Quote> > > Off the top of my head: A student can enroll in no more than X courses > per semester - so the occurrences of Course information for a student > would be limited to X occurrences. Also, there is a difference between trying to specify a structure for declarative purposes and for validation purposes. For validation, there is no need for {M,N}. For declaration (e.g. for use in documentation or to allow easy translation to arrays or some other implementation format) then {M,N} may be more useful. However, {M,N} is only one of a zillion kinds of semanticesque constraints that people have. Richard Tobin wrote: > Mike F wrote > > This ia not much of a deficiency, such constraints are rare and rarely > > useful. Though I did once get a bug report for XSV because it did not > > accept maxOccurs="4294967296". > Have to agree that it's not a big deficiency. Also, it is probably wrong-headed, if it supposes that schemas act to determine or checkthe capacity of a system. Having maxOccurs="4294967296" will not guarantee that your system will support 4294967296 occurrences. (SGML allowed a matching of document quantitie with system capacity, but I don't know whether it was actually much use.) Cheers Rick
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