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> In the vast majority of other cases, changing all of the existing > applications to accomodate a new consumer of the markup just isn't > reasonable, which leads to the slippery slope of wedging more > information into existing markup, or the new consumer just accepting > the existing markup. Or allowing non vocabulary owner extensibility so that the participating organisations that need a new peice of markup is not hamstrung by a lengthy ratification process and can use that (initially) private extension with its particular trading partners. It may be offered back to the vocabulary owner as a candidate for the next 'big bang'. Some see this approach as an equally 'slippery slope' that diminishes a community standard. Personally I don't, given that the alternative of a standards body deciding when and if I can start using a required piece of business data in [compatible] message exchanges provides no great encouragement to comply to the standard and typically forces business to 'go private' anyway. So I see the private extension mechanism as a practical approach to slow movement. I'm not saying it not without problems of course, but so is managing a completely private vocabulary with each of your trading partners. Fraser. On 03/01/2008, Andrew Welch <andrew.j.welch@g...> wrote: > On 03/01/2008, Stephen Green <stephengreenubl@g...> wrote: > > A fictionalization/generalization of one of the Invoice document features > > might serve to make this a little more realistic: > > > > A document type A has an IssueDate. The document was designed based > > on requirements from countries X and Y where the IssueDate means the date > > when the document was created. That's version 1. Along comes country Z > > where IssueDate is the date when tax was applied. That is for their country > > actually the only date which is meaningful on the document, they ignore the > > date the document was created. Because of the political and legal situation > > they insist on a new version being created which they claim is backwards > > compatible but where the definition of the IssueDate is changed a little. It > > is now, in version 2 a mixture of the two definitions such that all countries > > are happy with it. But then along comes country Q where the document > > type in question usually has both an IssueDate and a TaxPointDate and it > > is the TaxPointDate which has the purpose of date when tax is applied and > > the IssueDate is as it is with countries X and Y. If country Q arrives in the > > design committee just before the roll-out, in the rush they persuade the > > committee to add TaxPointDate to version 2. Now there is the likelihood of > > a semantic interoperability problem. Does country Z start using the > > TaxPointDate since it has an uncompromised definition which is exactly what > > they require rather than IssueDate which has a vaguer semantic definition and > > role. If they carry on using IssueDate then there is the risk it will > > be misunderstood > > by countries X and Y. > > The dates are the dates, they are fixed, it's just the interpretation > of those dates that differ, so you could just add a layer of > abstraction - call the dates date1 and date2 and let country1 treat > date1 as the IssueDate, and for country2 it would be date2. What you > gain in "semantic interoperability" you lose in the semantic quality > of the XML. > > An alternative is to add an "applicability" attribute to the elements, such as: > > <issueDate applicability="X">... > <issueDate applicability="Z">... > > or for more complex configuations use a child element: > > <container> > <applicability> > <details.../> > </applicability> > <issueDate>... > </container> > > ...which is the way they do it for various plane configurations in > S1000D (iirc - it was a few years ago now that I did that). The > processing application can then filter or ignore markup that's not > applicable to itself. Content with no applicability attribute or > child element is applicable to all. > > Huge markup efforts like S1000D and AvP70 have addressed most of these > problems, the people that designed that XML also designed the SGML > before it, and have coped with problems like versioning, multiple > variations for each country and per plane etc. so maybe learn from > their mistakes. They have massive committees that take a long time to > change a single attribute, and clear definitions to authors about the > intended use for each bit of markup - I've lost several enjoyable > hours ensuring that a 3rd level list used roman numerals, unless it > was within a numbered paragraph, in which case it becomes a 4th level > list. > > Anyway, my point is that for them the markup is the most important > thing - bigger than all of the applications that process it - so all > of the applications change when the markup changes. A new version is > a big event. > > In the vast majority of other cases, changing all of the existing > applications to accomodate a new consumer of the markup just isn't > reasonable, which leads to the slippery slope of wedging more > information into existing markup, or the new consumer just accepting > the existing markup. > > > > cheers > -- > Andrew Welch > http://andrewjwelch.com > Kernow: http://kernowforsaxon.sf.net/ > > _______________________________________________________________________ > > XML-DEV is a publicly archived, unmoderated list hosted by OASIS > to support XML implementation and development. To minimize > spam in the archives, you must subscribe before posting. > > [Un]Subscribe/change address: http://www.oasis-open.org/mlmanage/ > Or unsubscribe: xml-dev-unsubscribe@l... > subscribe: xml-dev-subscribe@l... > List archive: http://lists.xml.org/archives/xml-dev/ > List Guidelines: http://www.oasis-open.org/maillists/guidelines.php > >
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