XQuery, UPDATES and XML repositories

In certain discussions on the xml-dev mailing list it came to my attention
that the W3C is considering letting XQuery go to recommendation status without
UPDATE or DELETE semantics being a part of the recommendation. Below are
various comments I've made regarding the lack of a data manipulation language
for XML  and how it adversely affects XMl repositories like native XML
databases and XML-enabled databases.

1.)  What has struck me particularly as being unfortunate is that I've yet to
see an XML data
manipulation language with the simple SELECT-UPDATE-DELETE semantics that
users of relational databases (i.e SQL users) and hierarchical databases (i.e.
DL/I users) have had for years and have come to take for granted.

   I believe that the existence of such a language is important if Native XML
databases want to escape the problems that have faced Object Oriented
Databases and have made a few companies in that space switch sides (e.g.
eXcelon). OODBs are fractured and have no consistent DML between them and
secondly interaction with the database primarily occurs via programmatic
interfaces as opposed to via a DML (for those that support one).

  Once relational databases decided to borrow a few object oriented concepts
(hence Object Relational databases), OODBs began to seem less attractive and
have since failed to live up to their earlier promise.
OODBMSs started off as object persistence libraries/mechanisms (some of which)
happened to support transactions and failed to go beyond that. I see Native
XML DBs doing the same thing and repeating history specifically it looks like
the practice of having one language that does querying but expecting updating
and modification to be done programmatically is what has been embraced and is
being encouraged by the W3C.

With this in mind I wondered why no XML data manipulation language I have seen
is BOTH simple and contains update/modification semantics especially since
hierarchical databases store similarly structured data and have had this for

2.) Currently there is little difference between the functionality of XPath
2.0, XSLT and XQuery except for the existence of template rules in XSLT or the
lack of element constructors and function definitions in XPath 2.0.
I am aware that XQuery has proposals to add updates to the language and feel
that instead of releasing a language that is a slight variation of other
languages that are being worked on by other W3C working groups, the XQuery WG
should add much needed update/delete functionality to XQuery. Currently in
industry we have uniform ways of accessing data from XML repositories (XPath
and DOM) regardless of whether these repositories are content management
systems, native XML databases or relational databases that speak XML. The
XQuery WG could potentially create a uniform way of accessing this data AS
WELL AS modifying it, thus freeing users from being tied to product specific
update mechanisms including proprietary GUI tools, custom programmatic
interfaces, XML based update languages, etc.

3.) The time frame for XQuery release has been mentioned as a reason for the
dropping of update semantics from XQuery. I would like to implore to
reconsider the benefits of an later release of XQuery. Do the benefits of
releasing the XQuery recommendation sooner instead of later outweigh the
problems that will occur when as different vendors create proprietary
extensions to XQuery to support update/delete semantics or the additional
costs that users will incur from having to invest in training for XPath/XQuery
BUT still needing extra skills to operations as basic as changing the names of
elements nodes or updating attributes in an XML repository?

Links To Related Discussions On XML-DEV:

Mythical guardians will be instructed to ask visitors name, purpose of visit,
and whether they have an appointment instead of ancient riddles.

Do You Yahoo!?
Get your free @yahoo.com address at http://mail.yahoo.com

Received on Thursday, 27 December 2001 14:27:00 UTC