Query Languages for XML

Joe Lapp jlapp at acm.org
Mon Nov 17 14:45:05 GMT 1997

"Martin Bryan" <mtbryan at sgml.u-net.com> wrote:
>Joe Lapp wrote:
>>You might use XSL to create a replacement
>>document and then upload the replacement, but this is not
>>conducive to having many users concurrently querying and updating
>>the document (you'd have to lock the whole document).
>There is no need to lock the whole document, just that part of the document
>that consititutes an updatable record for the database it is being used to
>update or being updated from. Such a record could consist of a a number of
>contiguous fields, a set of discrete fields taken from appropriate parts of
>a document, or even a single field. There in no reason why fields not likely
>to be affected by change need to be locked in any way.

I agree that under the appropriate circumstances you wouldn't have
to lock the whole document.  However, were you to do the trick with
what is currently XSL, it seems to me that you would have to create
a _replacement_ document and then replace the original document.
If in the time between reading the original and generating the
replacement another user reads the original, and if you the other
user posts his replacement after you post your replacement, then
your changes do not take.

Or maybe you are suggesting there is no need to replace the whole
document using an XSL approach.  XSL or some other XML standard would
need to define a standard mechanism for identifying and modifying a
portion of a document.  I am aware of some sort of 'chunking'
initiative, but I don't know exactly what the scope of the effort is.
Joe Lapp (Java Apps Developer/Consultant)
Unite for Java! - http://www.javalobby.org
jlapp at acm.org

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