> Ok that fair enough but begs some questions
> 1. how do I know it is optional?
The clues are that they are not always set, the enumeration is
limited and the cardinality of the child link is 0..*.
This may sound weak, but it is like many bits of the data model to take a
random example: Experiment.sampleVolume - there will be a value but it
needn't be recorded. Things are just filled in by the user or application
as things are discovered or when they are needed.
T.
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Dr Tim Stevens Email: [log in to unmask]
Department of Biochemistry [log in to unmask]
University of Cambridge Phone: +44 1223 766022 (office)
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