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A data provider may implement extensions to a standard schema, such as the EPRI CIM or the RDF schema (described below).
Standard schema may be extended provided compatibility with standard clients is maintained. Extensions may be made as follows:
• The extension may add classes and/or properties.
• Classes may be added which are sub-classes or super-classes of standard classes.
• Properties may be added whose domain and/or range is a standard class.
• The URI of each added class or property must be unique. (Uniqueness may require the inclusion of the Internet domain name of the extender.)
• The definition of any standard property may not be changed.
• No sub-class/super-class relationships between standard classes may be altered.
Unlike standard schema, an extension is not necessarily agreed by more than one independent software developer. Therefore
schema extensions are not necessarily
published according to the rules in Section 7.2, “Industry and Application-Specific
Schema,? on page 7-2.
An implementation that extends a nominally standard schema in an incompatible way (violating one or more of the foregoing
rules) must rename the resulting schema or the affected elements so as not to conflict with a standard implementation.