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Hi Roger, I was actually a very determined opponent of NVDL until recently when, one day pacing around my office, I realized that there was a use for it. I agree it is good for validation of Compound documents, in the understanding of the Compound Document Formats group but definitely not for passing around data between systems, with the understanding that systems are probably big ERP systems with lots of programmers on them and complicated workflow etc. Why the first and not in the second one? Well, NVDL as I understand it (and this understanding was formed more than a year ago so perhaps it has changed since but I doubt it) does validation of the instance data and then leaves the various namespaces in the same instance. This is useful for a compound document in which the the various formats must interact in an a behavioral manner, such as creating a presentation of the data they represent. But if the format that is being transmitted is what is generally understood as data in nature, for example business data, NVDL encourages extension mechanisms that in my experience most ERP systems can not pragmatically be redesigned to handle, for example if I have a system that is supposed to handle the format Order in the Order namespace, if I later want to extend that format I can do so by specifying in the XML Schema way: extensions happen under the element with the name Extension, or I can specify that extensions are done in the NVDL way which is basically putting the extending markup wherever I want. I might prefer to do things the NVDL way but in this context I am talking about big systems with code in multiple places developed by many different people. In such a system people have probably made all sorts of assumptions about the data, perhaps because they have only seen examples of Order or read the Order schema, so that when one gets down to the part of Order that has the following structure according to the schema (the following obviously a bad example of business data as no exchange rate is defined etc. ): <payment> <paymentpart><currency>DKK</currency><amount>2700</amount></paymentpart> <paymentpart><currency>USD</currency><amount>120</amount></paymentpart> </payment> some programmers have done the following in some out of the way part of the system: when element = payment loop child nodes - addamount(node1,node2) end loop so when we send in new extended data <payment> <paymentpart><currency>DKK</currency><amount>2700</amount></paymentpart> <paymentpart><currency>USD</currency><amount>120</amount></paymentpart> <ex:paymentoccurrence><ex:paymentqualifier>SEK</ex:paymentqualifier><ex:time>2200</ex:time><ex:date>some date</ex:date></ex:paymentoccurence> </payment> The bugs introduced in such a scenario into these kinds of systems are, I think, somewhat harder to detect than bugs introduced in a browser. For this reason when it is business data that I am expecting to work in a bunch of systems over which I have no control and which has probably been developed by many different people I would prefer to have something more limiting in the structure allowed in to the internal processes of the system, even though personally, in my own life, I might prefer to have a freer and more extensible structure to the data I am working with. This paragraph is in fact a true representation of my feeling on the matter, so there's no need to explain to me how I need to learn to appreciate extensibility, I do appreciate it. I've just also seen some things that teach me that not everyone are set up to handle it. Cheers, Bryan Rasmussen On Tue, Apr 22, 2008 at 10:23 PM, Costello, Roger L. <costello@m...> wrote: > Hi Folks, > > This NVDL stuff has opened up new worlds in XML design for me. > > I've written a short article describing various ways to design an XML > instance document that is to contain diverse data: > > http://www.xfront.com/xml/design/compound-documents/index.html > > Comments welcome. > > /Roger > > _______________________________________________________________________ > > 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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