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941Re: Re-engaging

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  • yahoo@strongbrains.com
    Apr 1, 2001
    • 0 Attachment
      All the the forms you cite are technically valid. However, the only
      form that I know of that integrates well with RDF and with semi-
      structured databases is OMISSION OF THE ELEMENT. Looking into the
      future a little, I think that integration with RDF and such databases
      is important to keep our reengineering costs low and our data re-use
      high, so I recommend that a NULL be espressed by OMISSION OF THE
      ELEMENT.

      For example, given a structure of value like

      new Foo("a", null, "c")

      I recommend a serialization of form like

      <Foo>
      <m1>a</m1>
      <m3>c</m3>
      </Foo>

      I realize that this is not the most convenient answer for some
      existing software, so I do not recommend it lightly but only after
      some consideration and conclusion that it will pay us back because it
      allows more integration going forward.



      --- In soapbuilders@y..., "Dave Winer" <dave@u...> wrote:
      > Confusion.
      >
      > Bottom-line.
      >
      > Is <nil xsi:null="1"/> OK with you as a way of representing nil or
      null or
      > whatever in SOAP 1.1 as of 4/1/01?
      >
      > If not, what do you think is the right way to represent nothingness
      or
      > voidness or emptyness?
      >
      > Dave
      >
      >
      > ----- Original Message -----
      > From: <yahoo@s...>
      > To: <soapbuilders@y...>
      > Sent: Sunday, April 01, 2001 5:58 PM
      > Subject: [soapbuilders] Re: Re-engaging
      >
      >
      > > Hello. I'm trying to catch up now with the huge volume of
      discussion
      > > here, and, since I am not yet caught up, I will sometimes lack
      some
      > > of the context of a posting or will comment on something in
      advance
      > > of many subsequent comments. If you can tolerate that, thank you.
      > >
      > > Glen Daniels wrote "Re: null params in the BDG - I haven't seen
      the
      > > latest version, just the mails, so I just want to make sure it's
      > > clear in the text that the "nil" element name is not required -
      i.e
      > > <thisParam xsi:null="1"/> is just as good. A nit, to be sure..."
      > >
      > > There is much to be said about this.
      > >
      > > xsi:null has problems. For one, while the namespace referenced
      > > by "xsi" contained an attribute called "null" at the time the SOAP
      > > 1.1 specification was written, the Proposed Recommendation
      version of
      > > the W3C XML Schemas specification, March 2001, no longer contains
      an
      > > attribute of that name. This puts its use on pretty thin ice
      going
      > > forward.
      > >
      > > There is a similar attribute, now called "nil", described by the
      > > Schemas specification. It was renamed specifically to disclaim
      any
      > > definite relation to the idea of "null" in a programming language
      or
      > > database.
      > >
      > > This does not, ipso facto, mean that SOAP 1.1 messages may not use
      > > xsi:nil to signal null (whatever it is that null means). The
      > > relevant statement here is item nine in section 5.1 of the SOAP
      1.1
      > > specification, which says, roughly, that a "null" (whatever a null
      > > is) may be represented by (a) omission of the element that would
      have
      > > represented a value, (b) presence of the element that would have
      > > contained a value, but now bearing an xsi:null='1' attribute, or
      (c)
      > > any other signal that is agreed on by the communicating
      applications.
      > >
      > > Consequently, xsi:nil is legal, under clause (c) above, but would
      > > obviously benefit from some broad agreement on its use.
      > >
      > > That said, however, there are reasons to prefer omission of an
      > > element (option a) rather than presence with a special attribute
      > > (option b). These reasons will not generally be apparent if one is
      > > only considering RPC, nor will they typically be clear in the
      context
      > > of programming language structures. Where the difference matters
      is
      > > with databases, which are evolving to support a structure
      > > called "semi-structured" data, and in that situation an omitted
      > > element is very different from a present element with an
      attribute.
      > > The RDF Activity at W3C is also an example of a domain in which
      semi-
      > > structured data is important.
      > >
      > > The omitted element form corresponds much more closely with a
      > > database NULL and with semi-structured data. For this reason,
      > > believing that we want to have a serialization format that works
      well
      > > with databases and RDF as well as with traditional programming
      > > languages, I favor consistently representing a null by omitting
      the
      > > corresponding element.
      > >
      > >
      > >
      > >
      > >
      > >
      > >
      > >
      > > To unsubscribe from this group, send an email to:
      > > soapbuilders-unsubscribe@y...
      > >
      > >
      > >
      > > Your use of Yahoo! Groups is subject to
      http://docs.yahoo.com/info/terms/
      > >
      > >
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