/ 
XML-Validator-Schema-1.00
River stage zero No dependents
/ XML::Validator::Schema

NAME

XML::Validator::Schema - validate XML against a subset of W3C XML Schema

SYNOPSIS

use XML::SAX::ParserFactory;
use XML::Validator::Schema;

#
# create a new validator object, using foo.xsd
#
$validator = XML::Validator::Schema->new(file => 'foo.xsd');

#
# create a SAX parser and assign the validator as a Handler
#
$parser = XML::SAX::ParserFactory->parser(Handler => $validator);

#
# validate foo.xml against foo.xsd
#
eval { $parser->parse_uri('foo.xml') };
die "File failed validation: $@" if $@;

DESCRIPTION

This module allows you to validate XML documents against a W3C XML Schema. This module does not implement the full W3C XML Schema recommendation (http://www.w3.org/XML/Schema), but a useful subset. See the SCHEMA SUPPORT section below.

INTERFACE

  • XML::Validator::Schema->new(file => 'file.xsd')

    Call this method to create a new XML::Validator:Schema object. The only available option is file which is required and must provide a path to an XML Schema document.

    Since XML::Validator::Schema is a SAX filter you will normally pass this object to a SAX parser:

    $validator = XML::Validator::Schema->new(file => 'foo.xsd');
$parser = XML::SAX::ParserFactory->parser(Handler => $validator);

    Then you can proceed to validate files using the parser:

    eval { $parser->parse_uri('foo.xml') };
die "File failed validation: $@" if $@;

RATIONALE

I'm writing a piece of software which uses Xerces/C++ ( http://xml.apache.org/xerces-c/ ) to validate documents against XML Schema schemas. This works very well, but I'd like to release my project to the world. Requiring users to install Xerces is simply too onerous a requirement; few will have it already and the Xerces installation system leaves much to be desired.

On CPAN, the only available XML Schema validator is XML::Schema. Unfortunately, this module isn't ready for use as it lacks the ability to actually parse the XML Schema document format! I looked into enhancing XML::Schema but I must admit that I'm not smart enough to understand the code... One day, when XML::Schema is completed I will replace this module with a wrapper around it.

This module represents my attempt to support enough XML Schema syntax to be useful without attempting to tackle the full standard. I'm sure this will mean that it can't be used in all situations, but hopefully that won't prevent it from being used at all.

SCHEMA SUPPORT

Supported Elements

The following elements are supported by the XML Schema parser. If you don't see an element or an attribute here then you definitely can't use it in a schema document.

You can expect that the schema document parser will produce an error if you include elements which are not supported. However, unsupported attributes may be silently ignored. This should not be misconstrued as a feature and will eventually be fixed.

<schema>

   Supported attributes: targetNamespace, elementFormDefault,
   attributeFormDefault

   Notes: the only supported values for elementFormDefault and
   attributeFormDefault are "unqualified."  As such, targetNamespace
   is essentially ignored.
      
<element name="foo">

   Supported attributes: name, type, minOccurs, maxOccurs

<attribute>

   Supported attributes: name, type, use

<sequence>

<complexType>

  Supported attributes: name

<annotation>

<documentation>

  Supported attributes: name

Supported Built-In Types

Supported built-in types are:

string
boolean
integer
int
dateTime
NMTOKEN

Miscellaneous Details

Other known devations from the specification:

  • Only a single global element is allowed.

  • Global attributes are not supported.

  • Named complex types must be global.

CAVEATS

Here are a few gotchas that you should know about:

  • This module has only been tested with XML::Parser. It's definitely possibly it could break when used with other SAX parsers.

  • Line and column numbers are not included in the generated error messages. This should change soon.

  • No performance testing or tuning has been done.

  • The module doesn't pass-along SAX events and as such isn't ready to be used as a real SAX filter. The example in the SYNOPSIS works, but that's it.

BUGS

Please use rt.cpan.org to report bugs in this module:

http://rt.cpan.org

Please note that I will delete bugs which merely point out the lack of support for a particular feature of XML Schema. Those are feature requests, and believe me, I know we've got a long way to go.

SUPPORT

This module is supported on the perl-xml mailing-list. Please join the list if you have questions, suggestions or patches:

http://listserv.activestate.com/mailman/listinfo/perl-xml

CVS

If you'd like to help develop XML::Validator::Schema you'll want to check out a copy of the CVS tree:

http://sourceforge.net/cvs/?group_id=89764

AUTHOR

Sam Tregar <sam@tregar.com>

COPYRIGHT AND LICENSE

Copyright (C) 2002 Sam Tregar

This program is free software; you can redistribute it and/or modify it under the same terms as Perl 5 itself.

A NOTE ON DEVELOPMENT METHODOLOGY

This module isn't just an XML Schema validator, it's also a test of the Test Driven Development methodology. I've been writing tests while I develop code for a while now, but TDD goes further by requiring tests to be written before code. One consequence of this is that the module code may seem naive; it really is just enough code to pass the current test suite. If I'm doing it right then there shouldn't be a single line of code that isn't directly related to passing a test. As I add functionality (by way of writing tests) I'll refactor the code a great deal, but I won't add code only to support future development.

For more information I recommend "Test Driven Development: By Example" by Kent Beck.

SEE ALSO

XML::Schema

http://www.w3.org/XML/Schema

http://xml.apache.org/xerces-c/