& XSLT I like this one too and it has the advantage that more terms can be 
easily added eg:

<?xml version="1.0"?> 
<op:or xmlns:op="http://operator-ns"> 
  <op:and> 
     <a/> 
     <b/> 
    <d/> 
  </op:and> 
  <c/> 
    <op:and> 
    <a/> 
    <f/> 
    </op:and> 
</op:or> 

<!-- (a and b and d) or c or (a and f) --> 
etc

now can we write an xslt that understands "and" and "or" and optimises 
the dom parsing like a good compiler or interpreter would ...

Rick

Mukul Gandhi wrote:
>  The first approach looks good to me. But perhaps assigning a namespace
>  to operator elements could be a good idea (something like below).
> 
>  <?xml version="1.0"?>
>  <op:or xmlns:op="http://operator-ns">
>    <op:and>
>       <a/>
>       <b/>
>    </op:and>
>    <c/>
>  </op:or>
> 
>  On 12/12/06, Andrew Welch <andrew.j.welch@[...].com> wrote:
> > I've just had to design some XML to model items that can have "and"
> > and "or" relationships between each one.
> >
> > For example:
> >
> > (a and b) or c
> >
> > could be designed as:
> >
> > <or>
> >    <a>
> >    <and>
> >        <b/>
> >        <c/>
> >    </and>
> > </or>
> >
> > another option could be to rely on position:
> >
> > <a>
> > <and/>
> > <b/>
> > <or/>
> > <c/>
> >
> > and another could be model the relationships separately somehow:
> >
> > <relationships>
> >  <rel ref="r1" type="and">
> >    <ent id="a"/>
> >    <ent id="b"/>
> >  </rel>
> >  <rel ref="r2" type="or">
> >    <ent id="r1"/>
> >    <ent id="c"/>
> >  </rel>
> > </relationships>
> > <a id="a"/>
> > <b id="b"/>
> > <c id="c"/>
> >
> > Each has its own advantages/drawbacks.  Personally I like the first
> > technique, although it can get cluttered when there are 10+ items.
> >
> > Are there any better ways that I'm missing?
> >
> > cheers
> > andrew
> 
> 

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