Re: integrating assign in the standard

> These assign dependent processing
> patterns map-out to many essential and often non-trivial use-cases, and
> include: 
> 
> - support of (user) global variables in scripting languages written in 
> XSLT
> (like the XML-based layout scripting language of our publishing engine)
> 
> - efficient run-time traversal and processing of large networks while
> avoiding loops (like traveling salesman trying to mark paths that he has
> already visited, as he traverses the graph) 


It is well-known that many problems involving graphs, such as finding the
shortest path to traverse all nodes (the Traveling Salesman Problem), are
NP-Complete.

Therefore, it is simply a false statement that adding "assign" to a
language could result in the possibility to implement *efficiently* a
problem of the full-graph-traversal group.

Unless someone considers "efficient" a solution to an NP-Complete problem.

I want to congratulate the members of the XSLT WG for their hard work,
which is about to give us XSLT 2.0 -- a most powerful and elegant
functional language.

Thanks,
Dimitre Novatchev

  _____  

From: public-qt-comments-request@w3.org
[mailto:public-qt-comments-request@w3.org] On Behalf Of Andre Cusson
Sent: 04 July 2005 00:33
To: public-qt-comments@w3.org
Subject: integrating assign in the standard


Hi,

There has been recent issues and discussions about the support of "assign"
and associated functionality, ex: 
- the "Template recursion, StackOverflowError, saxon:while and variable
assignability" message track on saxon-help@lists.sourceforge.net,
continued
on 
- the " Eliminating
<https://sourceforge.net/forum/message.php?msg_id=3212142> saxon:assign"
message track of the source-forge Saxon OpenDiscussion forum at
https://sourceforge.net/forum/forum.php?thread_id=1305798
<https://sourceforge.net/forum/forum.php?thread_id=1305798&forum_id=94026>
&forum_id=94026 ).

Assign is currently an extension supported by some implementations (ex:
Saxon).  

Recently some have been proposing to drop assign from XSLT as there should
be other (more standard) ways to achieve equivalent results.  

We have been looking at this for little while and would like to propose
not
only that assign could be supported as an extension but that assign should
be an integral part of the XSLT standard for the simple reason that
important and fundamental processing patterns can not be efficiently
expressed in XSLT, without assign.  These assign dependent processing
patterns map-out to many essential and often non-trivial use-cases, and
include: 

- support of (user) global variables in scripting languages written in
XSLT
(like the XML-based layout scripting language of our publishing engine)

- efficient run-time traversal and processing of large networks while
avoiding loops (like traveling salesman trying to mark paths that he has
already visited, as he traverses the graph) 

- efficiently record and monitor global processes (like avoiding the
XSLT2.0
"Cannot write more than one result document to the same URI" error (and
avoiding duplicates/overwrites) when re-generating (ie. updating), from
its
XML sources, a web site, whose pages are already referred to by other
sites
and bookmarks, and where, while traversing the tree of source XML
documents,
at every page node, before generating the page, the transform needs to
check
if that URL has already been used, add it to the list of done pages if it
has not or report (ex: trace) the duplication.


For real-world examples, we have an XSLT application currently on-line,
with
about 25K lines of XSLT 2.0 and about 400 global variables of which 17 are
assignable variables that specifically fit patterns for which no other
equivalent algorithm could be found to replace the ones using assign,
confirming (still, so far), the requirements for Assign.

In fact, assign is so important, that it has to be part of the standard
(like regex, number formatting, escaping, html serialization, keys, etc.)
to
allow non-trivial applications to be conformant and portable.

In no way are we advocating that assign should be used in cases other than
those for which there is no reasonable alternative.

Of course, the name "assign" is not really important, but it is the
occasional mutability offered by the associated functionality that is key
and unique.

Do not hesitate to contact us for more information.

Thank you for your consideration.

Andre Cusson
T: (1) 514 583 0601
01 COMMUNICATIONS


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Received on Saturday, 16 July 2005 05:02:39 UTC