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    <title>PEP # ?:Supporting Dynamic Core Schema in Pegasus 2.2</title>
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	<h1>PEP # ?:Supporting Dynamic Core Schema in Pegasus 2.2</h1>
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	<th>Type</th><th>Status</th><th>Approveers</th>
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	<td>Architecture</td><td>Draft</td><td>Pegasus architecture team</td>
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	<th>Version</th><th>Date</th><th>Author</th><th>Comments</th>
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	<td>1.0</td><td>Fri Feb 28 09:51:20 2003</td><td>IBM/Mike Day
	</td><td><i>Design Proposal, to be extended with implementation details</i></td>
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	<h2>Summary</h2>

	<p>
	  The premise of CIM/Wbem is to provide normalized access to
	  heterogenous computing resources. This is a difficult
	  technical to solve but the benefits are tremendous for
	  writers of systems management software. 
	</p>

	<p>
	 The ability of CIM/Wbem implementations to provide normalized
	  access to heterogenous resources derives from the
	  extensibility of the CIM meta schema, or modelling
	  language. CIM models can be extended or revised
	  dynamically. There is limited polymorphism built into the
	  CIM Schema. 
	</p>
	<p>
	  CIM/Wbem does not isolate program code from data
	  model. Rather, it separates the access mechanism from the
	  resource. This means, for example, that specific schema
	  classes can be supported by custom source code. However, the
	  CIM/Wbem infrastructure which includes the access protocol,
	  schema repository, and operations, have no requirement to be
	  aware of specific schema classes. 
	</p>

	<p>
	  Most of Pegasus is implemented to take advantage of this
	  separation of infrastructure from resource
	  instrumentation. We can define new classes and provide
	  instances of those classes dynamically without modifying any
	  of the Pegasus source code. 
	</p>
	<p>
	  However in some critical infrastructure components,
	  Pegasus is hardcoded to support specific schema definitions
	  and classes. Further, it is hardcoded to preclude schema
	  extension for important portions of the CIM schema.
	</p>
	<p>
	  Schema components that are statically coded in Pegasus today
	  include the Provider schema, the Indication Schema,
	  and Authentication.
	</p>
	<p>
	  The static nature of the Provider, Indication, and
	  Authentication schemas causes Pegasus to enforce behavior
	  that is not the subject of any DMTF standards. For example, today
	  only C++ providers are allowed, and the provider interface
	  (which is not standardized) is statically hardcoded in
	  Pegasus from the Schema to the dynamic library support for providers.
	</p>
	<p>
	  Other examples of non-standardized behavior that is enforced
	  by hard-coded schema support in Pegasus include Indication
	  Handling, Indication formats, and authentication options.
	</p>
	
	<h2>Problem Solved/Feature Added</h2>
	<p>
	  
	</p>

	
	<h2> Proposed schedule.</h2>
	
	<h2>Risk Mitigation</h2>
	
    <hr>
    <address><a href="mailto:mdday@us.ibm.com">Michael Day</a></address>
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