..., null) ==^3.1

Actually, the method equals has to be called instead of the equality operator. The operator is used here for brevity only. However, most objects are implemented using flyweight pattern, so the equality operator would work as well.

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...   Basic.STRING^3.2

Class Basic contains predefined objects representing built-in OCL types.

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... optional.^3.3

This is slightly different from the UML, where an association class inherits from both association and class.

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... missing.^3.4

Additionally, tag names are different as explained above.

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