Re: View updating in practice?

Ohoo, this could be a long running thread :-)

Were you following the discussions eailer about Date & McGoveran's view updating scheme? If not, start from about message 169 on this thread http://groups.google.co.uk/groups?hl=en&lr=&ie=UTF-8&threadm=fedf3d42.02100108 58.76f2f1e5%40posting.google.com&rnum=1

(P.S. anyone know the best way to capture concise google groups URLs ?)

"Jens Lechtenbörger" <lechtej_at_uni-muenster.de> wrote in message news:m2of9087s0.fsf_at_pcwi1068.uni-muenster.de...
> Dear reader,
>
> I wonder if anybody uses view updates in practice and if so what
> kind of updates on what kind of views.
>
> Personally, I believe that view updates are dangerous in most
> situations as users cannot understand what is going on.

This is similar to my general feelings to. It is my position that unless views are 'information equivalent' to their underlying base relvars (which is, I believe is equivalent to taking a constant complement), then view updates should simply be seen as a shorthand - a way for users to get the DMBS to generate base update statements from the users desire of what the value of some relational expression looks like.

>To give two
> simple examples: In case of deletions from projections, users delete
> tuples they do not know completely. In case of insertions into
> joins, users do not know whether they are actually inserting into
> both operand relations or whether there was a dangling tuple in any
> of the operand relations that gets "absorbed" by the newly inserted
> tuple. It is easy to see that users will not be able to undo their
> view updates (such that the old _database_ state is reached) using
> further view updates in the above situations. If a was a user of
> such a database I would be very irritated.
>
> I wrote a paper on this topic for ICDT'03. (Take a look at
> http://dbms.uni-muenster.de/publications/downloads/view-updates.pdf
> if you are interested in the details.) Unfortunately, the paper got
> rejected, but I'm not convinced by the reviewers' critique ;) Now,
> I would like to know what people do in practice. My questions are
> as follows:

I'll read it over the weekend. I would be interested if you could briefly outline what the reviewers' critique was.

> 1. Do you use view updates? What is the scenario?
>
> 2. If you do _not_ use view updates, did you at least think about
> using them? If so, what was the application scenario and why did
> you not implement it (e.g., no support by DBMS or too complicated
> for users)?
>
> 3. Does anybody use SQL:1999 INSTEAD triggers to implement view
> updates?

I very probably will do when I get the chance to use DB2 V8 on a project (it's still in beta at present). In fact I could do with them on my current project, I'll write up the scenario here if I get the time.

> Thanks in advance,
>

Your welcome

Regards
Paul Vernon
Business Intelligence, IBM Global Services Received on Fri Nov 08 2002 - 20:52:05 CET