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version 1.1, 2003/02/28 21:33:22
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version 1.1.2.1, 2003/02/28 21:33:22
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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 |
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</td><td><i>Design Proposal, to be extended with implementation details</i></td> |
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<hr> |
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<h2>Summary</h2> |
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<p> |
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The premise of CIM/Wbem is to provide normalized access to |
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heterogenous computing resources. This is a difficult |
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technical to solve but the benefits are tremendous for |
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writers of systems management software. |
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<p> |
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The ability of CIM/Wbem implementations to provide normalized |
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access to heterogenous resources derives from the |
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extensibility of the CIM meta schema, or modelling |
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language. CIM models can be extended or revised |
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dynamically. There is limited polymorphism built into the |
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CIM Schema. |
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</p> |
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<p> |
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CIM/Wbem does not isolate program code from data |
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model. Rather, it separates the access mechanism from the |
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resource. This means, for example, that specific schema |
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classes can be supported by custom source code. However, the |
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CIM/Wbem infrastructure which includes the access protocol, |
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schema repository, and operations, have no requirement to be |
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aware of specific schema classes. |
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</p> |
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<p> |
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Most of Pegasus is implemented to take advantage of this |
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separation of infrastructure from resource |
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instrumentation. We can define new classes and provide |
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instances of those classes dynamically without modifying any |
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of the Pegasus source code. |
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</p> |
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<p> |
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However in some critical infrastructure components, |
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Pegasus is hardcoded to support specific schema definitions |
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and classes. Further, it is hardcoded to preclude schema |
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extension for important portions of the CIM schema. |
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</p> |
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<p> |
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Schema components that are statically coded in Pegasus today |
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include the Provider schema, the Indication Schema, |
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and Authentication. |
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<p> |
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The static nature of the Provider, Indication, and |
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Authentication schemas causes Pegasus to enforce behavior |
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that is not the subject of any DMTF standards. For example, today |
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only C++ providers are allowed, and the provider interface |
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(which is not standardized) is statically hardcoded in |
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Pegasus from the Schema to the dynamic library support for providers. |
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</p> |
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<p> |
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Other examples of non-standardized behavior that is enforced |
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by hard-coded schema support in Pegasus include Indication |
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Handling, Indication formats, and authentication options. |
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</p> |
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<h2>Problem Solved/Feature Added</h2> |
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<p> |
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</p> |
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<h2> Proposed schedule.</h2> |
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<h2>Risk Mitigation</h2> |
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<hr> |
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<address><a href="mailto:mdday@us.ibm.com">Michael Day</a></address> |
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<!-- Created: Fri Feb 28 09:49:31 EST 2003 --> |
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Last modified: Fri Feb 28 12:34:34 EST 2003 |
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