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From Benson Margulies <>
Subject How many XML Schema libraries at ASF is too many XML Schema Libraries?
Date Sun, 05 Apr 2009 21:38:09 GMT
Dear Xerces-J developers,

At the moment, I'm the most active maintainer of Apache Xml Schema. This
library, which lives inside the WS-COMMONS project, which lives inside the
Web Services TLP, is a set of Java classes that form a data model for W3C
XML Schema, together with code to walk DOM of schema documents and build the
representation and visa versa.

XmlSchema has no capability to validate a document against a schema. Typical
applications, such as Apache CXF or Apache Axis, spend a fair amount of time
converting back and forth between XmlSchema representation and the ordinary
DOM for schema documents, if only to pass them into the SchemaFactory to tee
up validation, or into some other library.

While I haven't gone spelunking in the code of Xerces yet, the existence of
the validation feature strikes me as strong circumstantial evidence the
existence of some representation of schema.

It strikes me that two Java class libraries for W3C XML Schema inside ASF
is, prima facia, one too many. So, I'm sending this email to ask if the
Xerces project has interest in working on exposing a documented API to the
XML Schema data model.

I was am more or less on the verge of putting a significant pulse of effort
into modernization and performance enhancement of XmlSchema, and if the same
effort could yield a more broadly useful result, I'd like to apply it there.

I am imagining a scheme where the core representation *is dom*, using
subclasses of DOM interfaces to supply convenience methods for safe and
comprehensible access to the abstract data model. This could radically speed
up code that needs to handle schema documents as DOM and also analyze and
manipulate the abstract data model of the W3C Xml Schema. But, imagination
aside, I think it would be good to focus energy on a shared solution.

Benson Margulies

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