[Saxdotnet-devel] Reducing the versioning / eliminating the Ixxx2 interfaces

[Jeff R. <li...@je...>]

Reducing the versioning / eliminating the Ixxx2 interfaces:
===========================================================

We are considering eliminating the versioning that exists in the API. As 
we are still early in the game and both implementations (Expat and 
AElfred) are active making such a change now seems plausible. We propose 
to eliminate the versioning by merging the Ixxx2 interfaces with the 
existing interfaces. This means, for example, merging the behavior of 
IAttributes2 with IAttributes and so on.

There are several problems that are created by doing this.

(1) Some implementations will not support the additional methods. Again, 
these extensions are not required by the XML Specification to be 
reported to the application. In such a case we will again turn to the 
SaxNotSupportedExcpetion. If someone attempts to access isDeclared for 
example and it is not supported by the implementation a 
SaxNotSupportedException should be thrown.

(2) In the case of IEntityResolver / IEntityResolver2, the resolveEntity 
function is duplicated. Because the implementation needs to know which 
function should be called (or worse both...) it is determined that the 
original resolveEntity signature be eliminated in favor of the newer 
signature from IEntityResolver2. So there will still be only one 
resolveEntity function and it would look like:

     InputSource ResolveEntity(string name,
                               string publicId,
                               string baseURI,
                               string systemId);


This will of course cause existing applications to fail. But, because 
this would be a compile time error the problem is mitigated.

(3) Modification to existing feature names for the Ixxx2 interfaces. 
Because the interfaces would no longer exist the feature names would 
become confusing. So we would change the feature names to:

    UseAttributes2Feature      --> AttributeDeclaredFeature
    UseLocator2Feature         --> XmlDeclFeature
    UseEntityResolver2Feature  --> UseExternalSubsetFeature

When the features are false the various extension callbacks (with the 
exception of the modified resolveEntity) would not be performed.

Thanks,
Jeff Rafter