ndg-xacml 0.5.0

XACML 2.0 implementation for CEDA (the Centre for Environmental Data Archival)
STFC, Rutherford Appleton Laboratory. This is follow on work from the NERC
(Natural Environment Research Council) DataGrid 3 Project.

XACML (eXtensible Access Control Mark-up Language), is an XML based language for
expressing access control policies.

See: http://www.oasis-open.org/committees/xacml/

Release 0.5.0
-------------
Major enhancements including additional language features and support for lxml:

* Optional support for lxml as alternative to ElementTree - gives better Xpath support
* Added concatenate functions and custom functions for URL encoding and MD5 hash custom functions.
* Added support for language features:
- for SAML 2.0 profile of XACML v2.0 (http://docs.oasis-open.org/xacml/2.0/access_control-xacml-2.0-saml-profile-spec-os.pdf)
- AttributeSelectors
- PolicySets.
- first-applicable rule combining algorithm
- Incorporated NOT and modified AND functions (from Prashant Kediyal).
* Support for adding custom functions with ndg.xacml.core.functions.FunctionMap.load_custom_function
* Fix for ticket:1130 and related bug
- In ndg.xacml.core.target.Target._matchChild, all SubjectMatches within a
Subject must evaluate to true for an overall match for the Subject (and
similarly for Resource, Action and Environment).
- In ndg.xacml.core.match.MatchBase, matching of the attribute value for a
SubjectMatch with any of the values for the selected attribute of the Subject
should result in an overall match (and similarly for Resource, Action and
Environment).

Release 0.4.0
-------------
Added support for custom DataTypes and functions. e.g.

# Add attribute value type
AttributeValueClassFactory.addClass('<my new type uri',
MyAttributeValueClass)

# ...and new parser for this type
DataTypeReaderClassFactory.addReader('<my new type uri',
ETreeMyDataTypeReaderClass)

# Add new function
functionMap['<my function type uri'] = MyNewFunctionClass

Release 0.3
-----------
Includes important fixes for equals functions, and improvement to at least one
member functions. Unit tests improved with wider coverage of different rule
definitions and example request contexts.

Improved and added to support for context handler and Policy Information Point
interfaces including the ability for the PDP to call back to a PIP via a
Context handler to retrieve additional subject attributes.

Release 0.2
-----------
Only the parts of the specification immediately required for CEDA have been
implemented in this initial release:
Policy Decision Point;
Deny overrides and Permit overrides rule combining algorithms;
AttributeDesignators;
various function types: see ndg.xacml.core.functions;
and attribute types: see ndg.xacml.core.attribute;
incomplete support for <AttributeSelector>s, <VariableReference>,
<VariableDefinition>. <Obligations>;
includes an ElementTree based parser for Policies. No support for writing
out policies or read/write of XML representation of <Request> and <Response>;

See ndg.xacml.test for unit tests and examples.

The software follows a modular structure to allow it to be extended easily to
include new parsers, functions and attribute types