On Friday, January 4, 2002, at 09:44 AM, [EMAIL PROTECTED] wrote:
These are very valid reasons, but I think it is very important for any database to be
able to offer data integrity and consistency. To me, ensuring that a document is valid
against some schema, is equivalent and just as essential as rdb's ability to enforce
constraints. And I would go further (in keeping with inevitable document composablity
/ fragment aggregation needs) and insist that inter-document consistency checking is
needed.
The W3C Xml Schema may well not be the best tool for this job, and I also would be
queasy about tying the server to some such standard at this point in time.
In an ideal
future, a mature xml database would support validation against any of the major
schema languages. Clearly that would be over-ambitious at this point, but perhaps
the server could be equipped with hooks for implementers to install the validation
mechanisms of their choice.
I think this is the likely path we'll pursue. There seems to be two major languages worth paying attention to, RelaxNG and W3C XML Schema. If both of those are supported most issues will be covered.
I'd like to here some opinions on DTDs though? So far we've been very anti DTD for the server. Does this make sense or should more attention be paid there?
As to performance, this may be the bias of my projects and experience, but I think
performance is most crucial in the accessing / query of documents, not the writing of
documents where the validation would take place. In most systems, large slow-
validating documents are not going to be added to the system with anything like the
frequency that accesses will take place. Frequent writes are more likely in systems
with smaller more data-centric document-records, whose validation shouldn'
t be as
time consuming. Small, frequent updates to large documents is another issue which
might require the development of validation methods that don't revalidate the entire
document. Performance should be a concern but not such a large one to negate the
need for server-side validation entirely.
You're probably not too far off here and I agree, we shouldn't let performance concerns stand in the way of getting the proper functionality in place. That's really been our goal all along anyway.
Eric
Kimbro Staken XML Database Software, Consulting and Writing http://www.xmldatabases.org/
