ModSAX: Proposed Core Properties

[Lars Marius Garshol]

* Ronald Bourret
|  
| What is the possible benefit of making any property write-only?
| That is, can any harm ever come from reading a property?

* David Megginson
| 
| There are three benefits:
| 
| 1. Keep the API absolutely as small as possible.
| 2. Avoid confusion.
| 3. Allow properties to be unknown until set.

These are all real benefits, but the disadvantage is rather large I'm
afraid: it makes assembling a processing solution from reusable
components much more difficult, since one component can't learn how
the others have modified the parser settings.

I think we should make all properties readable, which means we split
them into read-write/read-only properties. This should maintain
benefits 1 and 2 even better than the write-only/read-only split,
since most people probably expect read-write/read-only properties like
e.g CORBA attributes.
 
I also think we should go even further and make all features readable,
so that a filter can see if a feature has been enabled or not. Without
knowing the exact set of features I think disabling reading is
potentially very limiting.

| Any attempt to access a property can generate a
| SAXNotSupportedException (or the derived SAXNotRecognizedException),
| but there is no guarantee that they will be symmetrical.

Maybe we should have a SAXInvalidValueException too, so that the
parser/filters can reject invalid values without risking
misinterpretation on the part of applications/filters?

--Lars M.


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