XML as a programming tool

walter.kriha at systor.com walter.kriha at systor.com
Tue Dec 23 13:24:53 GMT 1997


>I found your analysis fascinating - though I didn't understand all of it.
>A few points.
It wasn't really an analysis. This stuff was implemented in a large
project about 2 years ago. And when we did it the reuse potential of SGML
in connection
with generic objects was much less clear than it looks now (:-)

>My query interface uses XLL TEIpointers, something like:
>Node node = tree.TEISearchFirstNode("DESCENDANT(1,MOL)");
>Since XLL systems are required to provide TEIaddressing, it's trivial to
>use it as a search query as well.
I haven't really studied TEI pointers yet. From what I remeber they look
like the HyTime tree addressing mode which I understand as basically giving
indices into a tree e.g. (1,2,3) meaning from the root element the second
child and from this the third child.But it looks like you can specify some
properties too.

This is surely a nice way to address things but if used in queries it seems
to bind the query to an exact tree layout. That' why I prefer purely
property based queries because then the locations of the elements can
change but my client still gets the information it wants (if it is still in
the tree somewhere). And change it will...

>>Solution: Turn some information tree into a blackboard.

>I suspect that XLL XML-LINK="EXTENDED" can be used here. This can be used
>to capture the non-hierarchical relations. How *generic* it can be, is
>something which I think we have not resolved.
I had something more profane in mind: if the implementation of a DOM node
also implements an observer interface then clients can register for changes
in elements or element content. This is a solution if you need to separate
publishers from subscribers without going to an object bus technology right
away. The document tree provides a structured medium for decoupled
communication between objects.

Thank you very much for your response and have a nice day,


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