[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: The meaning of the "string" datatype?
On 15 Apr 2009, at 07:20 , Rick Jelliffe wrote: > > This is of course a little topsy turvy. I had a case with an > insurance company who received data from the agents which had > standard fields but the fields could contain any notation. There was > a separate process where people would check the fields and "re-work" > them into the standard notations. So the input might have > <date>20th May, 2010</date> > and after rework it would contain > <date>2010-05-20</date> > > They were surprised to learn that they could not merely say that the > incoming data was a string, and then restrict this string to be a > date type. (Since xs:date is not a restriction of xs:string.) To make this idea of rework performing a restriction of the input, it would probably be better to define the input as having a type which is in fact restricted by date. For example, anySimpleType, or anyType. In XSD, date is not a restriction of string for much the same reason that in SQL, timestamp is not a subtype of VARCHAR, and in most programming languages, date objects or structs are not restrictions of char* arrays. If your interlocutors were programmers, I doubt they would have found it surprising. If they weren't, I think it may have been a mistake to assume that when they said 'string' they mean 'an instance of the xsd:string datatype'; it seems rather more likely that they meant simply untyped data. But I wasn't there, so I don't know. > The original XML Schemas datatype hierarchy was not designed with > document refinement in mind (i.e. marking up the document, passing > it as text through several different XML stages): That seems odd to me; it was certainly on the minds of some in the WG. Perhaps not on yours. But then I think it unwise to assume that processing a document through stages of a workflow will invariably result in restriction, or that the input and output of a transformation will always need to be described by the same schema. YMMV, of course. -- **************************************************************** * C. M. Sperberg-McQueen, Black Mesa Technologies LLC * http://www.blackmesatech.com * http://cmsmcq.com/mib * http://balisage.net ****************************************************************
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