W3C home > Mailing lists > Public > public-rdf-in-xhtml-tf@w3.org > August 2004

RE: Quick glance through xhtml2 meatainformation module

From: Mark Birbeck <mark.birbeck@x-port.net>
Date: Tue, 10 Aug 2004 19:55:06 +0100
To: "'Max Froumentin'" <mf@w3.org>
Cc: <public-rdf-in-xhtml-tf@w3.org>, "'Steven Pemberton'" <steven.pemberton@cwi.nl>
Message-ID: <002d01c47f0b$8d33da50$6701a8c0@W100>

Hi Max,

> The beginning of 20.4 says "Metadata that is relevant to a
> resource referred to by a link can be placed inside the link 
> element with no about.", but the example show a <meta> inside 
> a <link>.

I'll go through an example. Our document has a property a:a which is
resource R1:

  <link rel="a:a" resource="R1" />

In turn, the resource R1 has a property a:b, which is the literal L1:

  <meta about="R1" property="a:b">L1</meta>

All that 20.4 says is that these two statements can be 'chained', in that
the second triple has as its subject the object of the first triple:

  <link rel="a:a" resource="R1">
    <meta property="a:b">L1</meta>

Of course the second statement could have had a resource as its object
instead of a literal, in which case you would have needed link instead of
meta. But either syntax would have had as its subject the resource on the
triple above.

> Also, the same sentence is ambiguous about which <link> cannot have
> an about attribute. Seems obvious it's the inner one, but the 
> first time I read it I understood the outer one.

I see what you mean. Thanks for that.

> "Both the rel and rev attributes may be specified simultaneously."
> This puzzles me very much. In the case where one writes rel="A" 
> rev="B" doesn't it imply that A and B are necessarily Functional
> Inverse Properties?

No. If A has a property a:a, which has a value of R1, there is nothing to
stop R1 having a property a:b, which has a value of A. Unrequited love seems
a good example ;)

  <link xmlns:w="http://en.wikipedia.org/wiki/"

As you can see @rel and @rev are not meant to imply some sort of inverse -
that would come from some OWL layer, I would have thought. All these
attributes do is say that instead of the subject being first and the object

  s p o

you can reverse it:

  o p s

by using @rev instead of @rel.

It's not entirely necessary, but it does make certain constructions easier
to write.

I hope that helps in terms of understanding what we're trying to get at. The
feedback on this list is certainly helping us to look again at how we
explain some of these things, so thanks for that.



Mark Birbeck
x-port.net Ltd.

e: Mark.Birbeck@x-port.net
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Received on Tuesday, 10 August 2004 19:03:18 UTC

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