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nickerso / cellml-spec-sphinx-test

Testing sphinx+readthedocs+github for developing the CellML specification in reST.
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Redundant wording about encapsulation digraph? #7

Open jonc125 opened 11 years ago

jonc125 commented 11 years ago

Am I going mad, or are the two clauses in this definition equivalent?

The encapsulation digraph MUST NOT contain any loops, and MUST NOT
contain any cycles in the underlying graph (that is, it must be a tree).
agarny commented 11 years ago

If anything, I would say that the first clause implies the second one, but that the reverse is not true. So, personally, I would keep the first clause and remove the second one. Just my 2p worth...

jonc125 commented 11 years ago

Just looked up some definitions to be sure. A loop is an arc that pairs a vertex to itself; I'm not sure whether this counts as a cycle or not. A tree is a connected graph with no cycles, so the encapsulation digraph is more strictly a forest, since it might not be connected. So we ought perhaps to say:

The encapsulation digraph MUST NOT contain any loops or cycles in the underlying graph (that is, it must be a forest).