Comments on XLink embed behaviour

Dear Sirs:

I have several comments and concerns about the embed behavior, i.e,
show="parsed", in the XLink specification paper.

(1)  The use of the word "show" as the attribute name gives the
impression that you are limiting your thinking to *display*
characteristics of the data.  Doesn't this mindset limit the usefulness
of links for other (non-display) applications?

(2) A link behavior is needed which gives the ability to specify that
applications should treat the link abstractly as if the link contents
are truly embedded (i.e., applications can't tell the difference). 
Merely providing show="parsed" does not provide this functionality. It
is ambiguous. 

For example, suppose that I have an XML document that is created by
assembling XML data from various sources, using XML Link (with
show="parsed").  Suppose the XML document shows stock quotes, where the
quotes are gotten from, say, three different sources.

Such a document raises ambiguities for applications of the document. 
Consider writing an XML Schema for the document.  Should the schema
describe the structure of the document *after* the embedding process has
occurred (post link resolution), or, should the schema describe the
structure of the document *before* the embedding process has occurred
(pre link resolution)?  That will depend on how the implementor of the
XML Parser interprets the show="parsed" attribute in the XLink spec.

To further clarify my example, should the schema describe this version
of the document (the post link resolution version):

<?xml version="1.0">
<stocks xmlns="stocks.xsd">
   <stock>
      <tickername>MSFT</tickername>
      <company.name>Microsoft Corporation</company.name>
      <current.price>85 5/8</current.price>
      <change>+13/16</change>
      <previous.close>84 13/16</previous.close>
   </stock>
   <stock>
      <tickername>AAPL</tickername>
      <company.name>Apple Corporation</company.name>
      <current.price>55 3/4</current.price>
      <change>0</change>
      <previous.close>55 3/4</previous.close>
   </stock>
   <stock>
      <tickername>HD</tickername>
      <company.name>Home Depot</company.name>
      <current.price>61</current.price>
      <change>-1 3/8</change>
      <previous.close>62 3/8</previous.close>
   </stock>
      <tickername>LU</tickername>
      <company.name>Lucent Technologies</company.name>
      <current.price>65 7/16</current.price>
      <change>-1 5/16</change>
      <previous.close>66 3/4</previous.close>
   </stock>
</stocks>

Or, should the schema describe this version of the document (the pre
link resolution version):

<?xml version="1.0">
<stocks xmlns="stocks.xsd">
   <source show="embed"
           href="http://www.quote.yahoo.com"/>
   <source show="embed"
           href="http://www.stocks.com"/>
   <source show="embed"
           href="http://www.altavista.stktker.com"/>
</stocks>

The XLink specification needs to support some way of indicating whether
the XML parser (applications in general) should validate the pre link
resolution version versus the post link resolution version. 

(3) I am concerned that if this issue goes unaddressed by the XLink
committee, it will result in different, non-interoperable,
interpretations of link behaviors.

Thank you for your time.
 
                                Roger L. Costello

Received on Friday, 6 August 1999 07:01:28 UTC