[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message]

XLink resource confusion (long)

• From: jackson <jackson@d...>
• To: XML DEV <xml-dev@l...>
• Date: Tue, 01 May 2001 19:16:06 +1000

I am confused as to the meaning of 'resource' in the 
the XLink draft spec [Spec]. I'd be glad of any comments.

Quote 1, In [Spec] 2.3:

  "Definition: A local resource is an XML element that
  participates in a link by virtue of having as its parent,
  or being itself, a linking element".

That is, a local resource might be either:
- Interpretation 1.A: a linking element. Presumably either
  a simple or extended link.
- Interpretation 1.B: a child of a linking element.

Is a third interpretation possible?
- Interpretation 1.C: both 1.A and 1.B.

Issues:
- Is this optional? Do we get to choose?

- Local resources can only be elements, according to this
  definition. That is, text child nodes of linking elements
  are not considered resources.

How many and what resources are there in the following?:

  <par xlink:type="simple"
       xlink:href="...">
    <title>Bloody Stupid Johnson invented links</title>
      B.S Johnson, the Discworld's (reg.) most famous idiot
      inventor, was a pioneer of linking in document mark-up
      languages. All arcs were in-bound.
  </par>

How many resources? Possibilities:
- 1 resource: namely the 'par' element, presumably with its
  contents ('title' and the text).
  (Interpretation 1.A)

- 1 resource: the 'title' child element of the 'par' element.
  (Interpretation 1.B)

- 2 resources: the 'par' element (with or without contents?)
  and the 'title' child element (even though this is presumably
  already included as a part of the 'par' resource).
  (Interpretation 1.C)

Note:
The only real substance here is the text content of the 'par'
element, but by this definition it cannot be classified as
a resource. Of course, it is part of the 'par' element, but
there is no mention here of descendants of whatever type being
part of the resource. Presumably it is so, but is it specifically
stated somewhere?

Now, turning this example into an extended link:

  <par xlink:type="extended">
    <title>Bloody Stupid Johnson invented links</title>
      B.S Johnson, the Discworld's (reg.) most famous idiot
      inventor, was a pioneer of linking in document mark-up
      languages. All arcs were in-bound.
    <loc xlink:type="locator"
         xlink:href="..."/>
    <loc xlink:type="locator"
         xlink:href="..."/>
  </par>

How many resources now? Possibilities:

- 1 resource: namely the 'par' element, presumably with its
  contents. Only now, the locators form part of the local
  resource of the 'par' element instead of (or in addition
  to) serving as XLink elements.
  (Interpretation 1.A)

  This is probably not what is wanted.

- 3 resources: the 'title' element, and the two 'loc' elements.
  (Interpretation 1.B)

- 1 resource: the 'title' child element of the 'par' element.
  In this case we have (arbitrarily?) excluded the 'loc'
  elements from consideration as resources.
  (Interpretation 1.B, with a twist)

- 2 resources: the 'par' element (with or without contents?)
  and the 'title' child element (even though this is presumably
  already included as a part of the 'par' resource).
  Again, we have (arbitrarily?) excluded the 'loc' elements
  from consideration as resources.
  (Interpretation 1.C, with the same twist)

It is conceivable that it might be useful to know whether the
'title' child element and the text child of the 'par' element
are parts of the same resource or instead are one resource
(the 'title' element) and part of a second resource ('par').

Further complication:
Quote 2. In [Spec] 5.1.1 it says:

  'An extended link indicates its participating local
  resources by means of special subelements that appear
  inside the extended link. An entire subelement, together
  with all of its contents, makes up a local resource.

  The XLink element for local resources is any element with
  an attribute in the XLink namespace called type with a
  value of "resource".

  The resource-type element may have any content; whatever
  content is present has no XLink-specified relationship to
  the link.'

That is:
- Local resources are indicated by xlink:type="resource"
attributes.
- At least here we understand that the contents of a resource
element are part of the resource.
- Only element child nodes ("subelements"?) can be resources.
So once again text content of an extended link cannot be
considered a resource?

This gives:
- Interpretation 2: Each subelement of the link which has
  attribute xlink:type='resource'.

Taking the example above:

  <par xlink:type="extended">
    <title>Bloody Stupid Johnson invented links</title>
      B.S Johnson, the Discworld's (reg.) most famous idiot
      inventor, was a pioneer of linking in document mark-up
      languages. All arcs were in-bound.
    <loc xlink:type="locator"
         xlink:href="..."/>
    <loc xlink:type="locator"
         xlink:href="..."/>
  </par>

What are the resources under interpretation 2? Possibilities:

- 0 resource: No xlink:type='resource' elements.

  However, at least we can say that the 'loc' elements are not
  resources.

Changing the example by adding an xlink:type='resource' to
the subelements without an xlink:type attribute.

  <par xlink:type="extended">
    <title xlink:type="resource">
      Bloody Stupid Johnson invented links
    </title>
      B.S Johnson, the Discworld's (reg.) most famous idiot
      inventor, was a pioneer of linking in document mark-up
      languages. All arcs were in-bound.
    <loc xlink:type="locator"
         xlink:href="..."/>
    <loc xlink:type="locator"
         xlink:href="..."/>
  </par>

Result is that we now have the title as a resource of the
extended link. But we cannot indicate that the text of the
'par' (the substance) is a resource.

Note:
XLink+XPointer would allow the text content to be indicated
as a _remote_ resource.

Issue:
If all sub-elements which are resources need to be named as
such using xlink:type='resource' attributes, we can't have
resources which contain more than one element. For example,
it is not possible to have a resource consisting of multiple
'par' elements, as in this case:

  <section xlink:type="extended">
    <title xlink:type="resource">
      Bloody Stupid Johnson invented links
    </title>
    <par xlink:type="resource">
      B.S Johnson, the Discworld's (reg.) most famous idiot
      inventor, was a pioneer of linking in document mark-up
      languages. All arcs were in-bound.
    </par>
    <par xlink:type="resource">
      At the time of B.S Johnson there were no computers in
      the Discworld (reg). Hyperlinking did not take off in
      a big way.
    </par>
    <loc xlink:type="locator"
         xlink:href="..."/>
    <loc xlink:type="locator"
         xlink:href="..."/>
  </section>

In this case we may want the two 'par' elements as separate
resources, but we might also want them to be one resource.

Under interpretation 1.A this is possible (without the explicit
xlink:type='resource' attributes), but not under interpretation
1.B or interpretation 2.

Questions:
- Can these quotes be reconciled?
- Which interpretation is correct?
- Am I missing something obvious?

Reference:

[Spec]: XLink draft spec (2000-12-20), http://www.w3.org/TR/xlink/

Thanks.

David Jackson

• Follow-Ups:
  • Re: XLink resource confusion (long)
    • From: "Christopher R. Maden" <crism@m...>
  • Re: XLink resource confusion (long)
    • From: "Eve L. Maler" <eve.maler@e...>

• Prev by Date: Re: Parser torture documents
• Next by Date: Re: XLink resource confusion (long)
• Previous by thread: RE: Parser torture documents
• Next by thread: Re: XLink resource confusion (long)
• Index(es):
  • Date
  • Thread