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Existence is one constraint statement that can be made using ADL/AOMÂ about attributes in a reference model. In ADL as statement will look something like:
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ELEMENT matches { value existence matches {1} matches* } |
This indicates that the value attribute has to be present. In fact, to this point such statements do not occur in ADL; only statements that an attributes existence is optional occur.
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ELEMENT matches { value existence matches {0..1} matches* } |
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