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Re: SVG WG Last Call review of XLink 1.1

From: Norman Walsh <Norman.Walsh@Sun.COM>
Date: Wed, 18 Jan 2006 16:42:21 -0500
To: Chris Lilley <chris@w3.org>
Cc: www-xml-linking-comments@w3.org
Message-ID: <87zmltdxhe.fsf@nwalsh.com>
/ Chris Lilley <chris@w3.org> was heard to say:
[...]
| Therefore, the wording at
| http://www.w3.org/TR/2005/WD-xlink11-20050707/#markup-reqs
| is very useful:
|
|   "2. it does not have a type attribute from the XLink namespace and it
|   adheres to the conformance constraints imposed by the XLink simple
|   element type, as prescribed in this specification."
|
| However, this text is contradicted in several places as noted below.

Thank you. Those were editorial oversights and have been corrected.

| 2.1) type attribute still sometimes required
|
| It seems that if the href attribute is *not* supplied, which is allowed
| by XLink 1.1, the type="simple" must be supplied - is that intentional?

Yes.

| SVG WG is okay with this restriction, if it was intended, but would
| prefer not to have this restrivtion.

That is the way that our note about extending XLink was worded and
that is how our charter was determined.

I can see your point, but requiring xlink:href or xlink:type has the
virtue that it does not require applications to treat

  <foo/>

as if it was an xlink:type="simple" link :-). I suppose we could have
chosen a different wording (something along the lines of "if any
attribute from the XLink namespace is used...") but we didn't. Given
that a simple link without an xlink:href is likely to be uncommon, and
our goal was ease of use, this seems a reasonable compromise.

| 2.2) Specification text contradictory
|
| 4.1 XLink Attribute Usage Patterns
| http://www.w3.org/TR/2005/WD-xlink11-20050707/#d0e594
|
| states, for simple links
|
|   "At least one of type or href must be specified".
|
| However,
|
| http://www.w3.org/TR/2005/WD-xlink11-20050707/#link-types
|
| states
|
|   "The value of the type attribute must be supplied."
|
| We assume the latter is an editorial oversight and this should in fact be
| something like:
|
|   The value of the type attribute must be supplied, unless a simple link
|   is required and an href is supplied.

Exactly.

| Similarly in
| http://www.w3.org/TR/2005/WD-xlink11-20050707/#simple-links
|
|   "The XLink element for simple links is any element with an attribute
|   in the XLink namespace called type with a value of "simple""
|
| is incorrect and is contradicted by the example that follows it. We
| suggest that it should be something like
|
|   The XLink element for simple links is any element with either a) an
|   attribute in the XLink namespace called href and no attribute in the
|   XLink namespace called type, or b) an attribute in the XLink namespace
|   called type with a value of "simple".

Exactly.

| 2.3) DTD fragment contradicts spec
|
| The following DTD sample from the specification
|
| <!ATTLIST commandname
|   xlink:type      (simple|none)   #REQUIRED
|   xlink:href      CDATA           #IMPLIED>
|
| seems to give the impression that type is required. We suggest replacing
| this with a more expressive RelaxNG snippet which states that if href is
| supplied, the type attribute is optional. The relevant portion of
| Appendix D may be suitable:
|
| simple = element * {
|     (simple.type | href.att | (simple.type, href.att)),
|      foreign.att*, role.att?, arcrole.att?, title.att?,
|      show.att?, actuate.att?,
|      (anyElement | text)*
|     }

Indeed. Improving the examples is on my list.

| 2.4) Example incorrect in 5.2
| The example with the caption
|
|   Example: Sample simple-Type Element Declarations and Instance
|
| http://www.w3.org/TR/2005/WD-xlink11-20050707/#simple-links
|
| is incorrect.
|
|   xlink:role      NMTOKEN         #FIXED "http://www.example.com/linkprops/student"
|
| xlink:role
| E The defaultValue "http://www.example.com/linkprops/student" of
| attribute "xlink:role" is not legal as for the lexical constraints of
| this attribute type.
|
| This should be CDATA not NMTOKEN

Fixed.

| 3) Reserving all attributes in the XLink namespace.
|
| This is a useful clarification.

Thank you.

| 4) Allowing IRIs.
|
| 4.1) Inadvertent text from XLink 1.1
|
| In section 5.4 Locator Attribute (href)
| http://www.w3.org/TR/xlink/#link-locators
|
|   "The value of the href attribute must be an IRI reference as defined
|   in [IETF RFC 3987] or must result in an IRI reference after the
|   escaping procedure described below is applied."
|
| That text is incorrect, and seems to be the result of a search and
| replace of URI for IRI. The whole point is that the escaping is not
| required in the XML instance, and is defined by the IRI specification

Thanks. This text is being reworked to make all the specifications in
the XML family consistent in this regard. It will be fixed in the next
draft.

Please let us know if you are satisfied by these resolutions to your
issues.

                                        Be seeing you,
                                          norm

-- 
Norman.Walsh@Sun.COM / XML Standards Architect / Sun Microsystems, Inc.
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Received on Wednesday, 18 January 2006 21:42:44 GMT

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