Response to LC-61 Issue

Dear Dario de Judicibus:

The XML Schema Working Group has spent the last several months
working through the comments received from the public on the last-call
draft of the XML Schema specification.  We thank you for the comments
you made on our specification during our last-call comment period, and
want to make sure you know that all comments received during the
last-call comment period have been recorded in our last-call issues
list (http://www.w3.org/2000/05/12-xmlschema-lcissues).

Among other issues, you raised the point registered as issue 
LC-61. simple-records: Allow record-style simple types?

Please see the discussion below, and respond as to whether
this resolution is satisfactory.



LC-61. simple-records: Allow record-style simple types?
-------------------------------------------------------

Issue Class: D Locus: datatypes Cluster: 03 constructors Status:
resolved
Assigned to: Frank Olken Originator: Dario de Judicibus


Description
------------

Should the datatypes spec be modified to allow the construction of types 
with simple internal structure (e.g. to allow both quantity and units 
of measure to be captured in the same simple type)?

Interactions and Input
----------------------

Cf. Suggestion: Microparsing support in XML Schema
Input from Dario de Judicibus:
"Dario de Judicibus" <ddj@mclink.it> to XML Schema Comments list, 
Tue, 25 Apr 2000 23:12:02 +0200

Final comment: there is no way to combine types. For example, if I have 

<xsd:simpleType name="units">
  <enumeration value="cm" />
  <enumeration value="in" />
</xsd:simpleType>

I have no way to define 
<height>12.4cm</height>


by combining xsd:decimal and units. That might be very useful. 
We might use a variant of pattern for that: 

        <xsd:complexType name="heightWithUnits">
                  <xsd:pattern>
                    <xsd:part type="xsd:decimal" />
                    <xsd:part value="\p{Zs}*" />
                    <xsd:part type="units" />
                  </xsd:pattern>
                </xsd:complexType> 



Input from Curt Arnold:
----------------------
Curt Arnold <carnold@houston.rr.com> to XML Schema Comments list, 
Wed, 26 Apr 2000 07:56:59 -0500

The schema group stated that aggregate types were outside the 
scope of the initial version. Derivation by list was a hard fought 
exception to that principle. 
If you are interested in discussions of dimensional units in XML, 
I can send you URL's to quite a few discussions. 

Input from Martin Bryan <mtbryan@sgml.u-net.com>:
-------------------------------------------------
"Martin Bryan" <mtbryan@sgml.u-net.com> to XML Schema Comments list 
on Sun, 14 May 2000 08:01:08 +0100 

The one area I still expect we are going to have problems in 
using datatype for electronic commerce is measurements. 
For example, how can I check that 100cm and 1m are exactly equivalent, 
but 1yd is not. But again I do not expect you to have addressed 
these problems at this state.
(Schema2 will be along within a few years!) 

Actual Resolution
-----------------

Discussed at Edinburgh Face to Face meeting.
We think it would be unwise to introduce secondary notations 
for representing structures which can be represented 
satisfactorily using XML.

Explanation (by F. Olken)
-----------

        Various versions of this issue were the subject of
considerable debate.  The WG rejected the proposed changes
on the grounds that the requirement could be reasonably met
by use of some additional markup (in most cases), for example:

        <length>
                <value> 5.25 </value>
                <units> inches </units>
        </length>

The working group recognizes that such constructions
are not useable as single XML attributes.


The WG was reluctant to go down the route of allowing further
grammatical structure within elements/arguments, allow the WG
felt obligated to preserve legacy composite structures such as 
IDREFS, etc.

Essentially, the Working Group felt that the existing XML
facilities could (largely) meet this requirement, and that
further elaboration of the language was undesirable, especially
in light of other comments we received that XML Schema Language
was already too baroque.

Another reason for this reluctance is that the measurement
units application would eventually require more complex notations 
such as:

        <density> 5 kg/(meter^3) </density)

which would require more elaborate grammars.

The measurement units application is dear to my heart,
and you are encourage to peruse the materials referenced
from the web page:

        http://pueblo.lbl.gov/~olken/mendel/units/units.htm

for a more extensive treatment of how to encode measurement
units into XML.


Is this response adequate ?
------------------------------

We (XML Schema Working Group) want to know your opinion
of our response to your last call comments.  This information
will be included with the package submitted to the W3C
Executive Director as part of the recommendation to take
the XML Schema Language to Candidate Recommendation.
We would appreciate your response as soon as possible.

Please choose from one of the following responses, adding 
whatever details, explanation you wish:

1)  "Good enough"  - You are satisfied with the Schema WG response
to your comments on XML Schema Language.  The response meets 
your requirements.  The matter may be considered resolved.

2) "Stop the presses"  - You are not happy with the response
to your comments on XML Schema Language.  Either the response
is unclear or inadequate.  The issue is of sufficient importance
and urgency that you want it called to the attention of the 
W3C Executive Director and you ask that the XML Schema Language 
delayed in advancing to Candidate Recommendation until the 
issue is resolved. 

3)  "Later - Version 1.1"  - You are not happy with the response,
but are prepared to defer reconsideration until XML Schema Lang.
Version 1.1 is drafted.  It is anticipated (hoped) that Version 1.1
will be completed by mid-2001.  Version 1.1 is intended primarily
to fix small issues needed by other W3C Working Groups to proceed 
with their work (especially XML Query Language).  You request that
your comments be reconsidered when drafting the Version 1.1 
requirements document.

4) "Later - Version 2.0"  - You are not happy with the response,
but are prepared to defer consideration until XML Schema Language
Version 2.0 is drafted.  It is anticipated that Version 2.0 would
not be completed until late 2001 or early 2002.  Version 2.0 may
include major revisions, e.g., multiple inheritance, etc.
You request that your comments be reconsidered when drafting the 
Version 2.0 requirements document.

5) "No longer care"  - You are not happy with the response, but
no longer care to pursue the matter, because ....



                  Frank Olken
                  XML Schema Language Working Group

  Lawrence Berkeley National Laboratory   (510) 486-5891 (voice)
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  E-mail:  olken@lbl.gov
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Received on Thursday, 28 September 2000 20:24:29 UTC