[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: XML Schemas: Best Practices
Caroline wrote: "The way in which I saw it was that a 'class' would indeed by analogous to the 'type' definition..." The FpML Architecture (http://www.fpml.org/spec/2000/tr-fpml-arch-1-0-2000-09-25/index.html - you have to register) from September of this year in its content model has a fairly thorough set of guidelines for taking the elements of a UML Class diagram and representing them in XML - they include aggregation, subtypes, classes, association and aggregation of subtypes. Yours, John F Schlesinger SysCore Solutions 212 619 5200 x 219 917 886 5895 Mobile -----Original Message----- From: Caroline Clewlow [mailto:cclewlow@e...] Sent: Thursday, October 12, 2000 6:24 AM To: xml-dev@l... Subject: Re: XML Schemas: Best Practices I would agree with making this analogy to object-oriented programming. I had a similar idea. The way in which I saw it was that a 'class' would indeed by analogous to the 'type' definition, and the object that is the instantiation of the class would reflect the 'element' based on that 'type'. I also saw the use of 'ref' as being similar to the use of a 'pointer' variable in programming. i.e. when would you use an object instance and when would you use a pointer to an object ? If you created a schema that contained elements which would only ever be used as children of elements in a seperate schema, these could be declared as types, and the 'instance' of the type created in the accompanying schema. I hope the above makes at least some sense ;-) Caroline Clewlow DERA, UK --- In xml-dev@e..., Caroline Weller <caroline.weller@a...> wrote: > > > Caveat: I have not spent much time looking at XMLSchema yet. > > I do agree with the use of type: > user defined types of data that are used to define many elements that have > different purposes. > The handling of those different elements might be different. > > An analogy from another area would be in object-oriented programming: > "When would you just instanciate a class (the element being the class), > and when would you create a subclass (the type being the parent class)" > > Do people think this analogy is useful? > > PS: love the spelling of Sydney, or maybe he meant the height of a guy called > Sidney? > :> being from Canberra, I found that quite amusing...... > > > Caroline Weller > Australian Bureau of Statistics. > > > > |--------+-----------------------> > | | "Roger L. | > | | Costello" | > | | <costello@mit| > | | re.org> | > | | | > | | 11/10/2000 | > | | 09:42 PM | > | | | > |--------+-----------------------> > >-----------------------------------------------------------| > | | > | To: xml-dev@l..., "Ripley,Michael W." | > | <rip@m...> | > | cc: costello@m..., "Cokus,Michael S." | > | <msc@m...>, "Pulvermacher,Mary K." | > | <pulver@m...>, "Heller,Mark J." | > | <heller@m...>, JohnSc@c..., (bcc: | > | Caroline Weller/Staff/ABS) | > | Subject: Re: XML Schemas: Best Practices | > >-----------------------------------------------------------| > > > > [Here's a response that I received directly. Any comments on it?] > > >"When should an item be declared as an element versus when should an > >item be declared as a type?" > > I think it's a matter of style. As you showed in your examples, you > can basically get done what needs to get done with either method. > > My take on the style would be: > > - use an element when all components of the element declaration will be > reused and semantically the reuse will mean the same thing (Elevation, > BostonElevation, FrankfurtElevation, SidneyElevation, etc.) > > - use a type when the type definition will be reused for semantically > different elements (e.g., a 'money' type definition that is reused for > elements UnitPrice, Subtotal, ShippingAndHandling, Total, etc.).
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