[DFDL-WG] Action 189 - revise precedence order section

[Mike Beckerle]

I suggested revising the precedence order section.

So, I spent a few hours trying to reinvent the precedence order section
along the lines of the grammar version 007.

I failed.

I kept ending up with a structure not too different from what exists
already in the spec.

The thought process goes something like this:

   - Create a tree corresponding to the grammar
   - Annotate the leaves with every relevant property.
   - Annotate the interior nodes of the tree with the properties needed
   just to get to that node of the tree, or that appear beneath that node down
   multiple paths.
   - And finally, don't repeat things.

The problem: the grammar productions and terminals don't provide enough
ways to share to avoid lots of duplication. The grammar leaves out exactly
the details needed - representation (the grammar regions often have both a
textual and a binary personality that are quite different), and length (the
grammar regions are mostly silent about lengthKind).

You end up wanting to create a big class diagram and have each node of the
tree associated with multiple classes. It's a mixin-style
multiple-inheritance scheme. It's not very interesting because so many
things inherit so many properties (because they have both textual and
binary forms, and work with different length kinds.)

If you approximate this by what you can create in a nested hierarchy, you
have to repeat some properties, but you end up being not very different
from the breakdown of what is called out in the precedence section of the
document as written currently.....

voila... full circle.

I went round and round this enough times to convince myself that whatever I
was producing wasn't adding value over what is already there in the
precedence section as written today.

I also convinced myself that the precedence section as written, does add
substantial value exactly because it is NOT organized along the lines of
the grammar, but orthogonally to it.

I suggest we close out Action 189. I think it will not pan out. There may
be other adjustments to be made to the precedence section, but the rewrite
along the lines of the grammar is not an idea that will pan out.

...mikeb
-- 
Mike Beckerle | OGF DFDL WG Co-Chair
Tel:  781-330-0412
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.ogf.org/pipermail/dfdl-wg/attachments/20121119/bd8b3a55/attachment.html>