Re: About XML to multiple language/multiple outputs

Subject: Re: About XML to multiple language/multiple outputs
From: Matthias Clasen <clasen@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Date: Thu, 26 Aug 1999 21:49:15 +0200
> > > 
> > One can, perhaps, define both query and element rules on terms of an
> > abstract query rule, not present in the language specification. 
> > 
>    Actually, I believe (without having worked out all the details, of
> course), that the existing query rule would be sufficient for this.
> We know, for sure, that any other type of rule can be rewritten as a
> query rule because the query rule allows node selection via an
> arbitrary SDQL expression.  The only potential problem is enforcing
> the specificity rules that DSSSL requires.
>    I believe this can be done with the priority expression part of the
> query rule by calculating a priority for each rule (thus, the basic
> query rule itself would be translated into our "baseline" query rule,
> so that we can alter the priority expression result).  For instance,
> we would automatically just add a large constant on to the result of a
> query rule's priority expression, and we would calculate the priority
> of an element rule based on the specificity of its gi or qualified-gi
> argument.
>    The problem would, of course, come into play in that the user can
> have their priority expression generate an arbitrarily large value, so
> we could run into a problem where their value is so large that adding
> anything on to it would cause an overflow.  Of course, if they're
> generating values that large, they're risking overflow, anyway, so
> maybe it isn't as much of a concern.  But, then, on the same note,
> could we really decide what the constant would be that we would add to
> query rule priorities, given that it has to insure that even a query
> rule with a priority of 0 would outweigh any other rule?  Picking an
> arbitrary value for this would, essentially, put a cap on how specific
> a qualified-gi in an element rule could be.  However, such a
> qualified-gi as might overflow such a limit is probably not a
> practical reality, so, again, I wouldn't worry too much about it.
>    So, does anyone else think we need to move this discussion to a new
> list: dsssl-guts? :)
> 

I think a proper way to transform all rules into query rules 
without risking overflows would need a slight extension of
the priority expression: Allow it to be a pair (or even list)
of numbers, sort them lexicographically. Maybe that
is the `abstract query rule' Avi was thinking of.

-- 
Matthias Clasen, 
Tel. 0761/203-5606
Email: clasen@xxxxxxxxxxxxxxxxxxxxxxxxxx
Mathematisches Institut, Albert-Ludwigs-Universitaet Freiburg


 DSSSList info and archive:  http://www.mulberrytech.com/dsssl/dssslist


Current Thread