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RULE (Rules can be written in separate RULE_SCHEMA)
New tokens (reserved words):
ALL_CROSS_MODEL_REFS_TO_ME
ALL_LOCAL_REFS_TO_ME
END_ENTITY_EXTENSION
ENTITY_EXTENSION
END_ EXPRESS_EXTENSION_SCHEMA
EXPRESS_EXTENSION_SCHEMA
SUBTYPES
Compiler checking
In addition to the “standard compilation time checking” during defining (compilation) of an extension schema, the following will be checked:
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3) All ENTITY names must be unique in the collection of Express schema and all extension schemata for the actual Express schema.
4)In addition to the rule in the Express language for “unique attribute names in an Entity declaration” , attribute names must be unique in the collection of all ENTITY_EXTENSION for a particular entity in all extension schemata for the actual Express schema.
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