UML14 — OCL: Are keywords reserved or not

Although the OCL specifies a respectable set of keywords (like
"and", "if", etc.) the OCL reference says nothing about whether
they are reserved or not. Clearly, a software designer is completely
free to specify the class with an attribute called "if". Or, more
probably, "context". Or any other OCL keyword. How, then, to
parse an OCL constraint like:

context if : X inv:
if.then->size()>=else->size()

(where if is used instead of self to designate the object an
invariant is applied to, and then and else are its associations).

Clearly, reserving keywords is a bad idea. The rule, which seems
to work well (and has been tried in many real programming
languages over decades) is:

An identifier is recognized as a keyword if and only if it is
encountered in a context where this keyword can legally
appear.

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