[henshin-dev] Injective Matching & Multi Nodes

[Sebastian Gabmeyer <sebastian.gabmeyer@xxxxxxxxxxxx>]

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Hi!

I just realized that the injectivity of a match from LHS to the host
graph is enforced across NACs, that is, if a node n1:N from the LHS is
mapped to some node h:N in the host graph, a node n2:N in a NAC that
is not mapped to n1 cannot be mapped to h (this is correct, isn't
it?).  I was wondering if there are any theoratical restrictions that
require this behavior?  In essence, I expected that the NAC, if not
explicitly mapped to some node from the LHS, would map to _any_ node
(in particaluar, including any nodes mapped from the LHS to the host
graph), as this would simplify the specification of the NAC.

Concerning multi-nodes I was wondering whether there is a semantic
difference between a NAC that contains multi-nodes and an equivalent
NAC where all multi-nodes have been replaced by single-nodes?  (To me
they'd be equivalent, as both would explore _all_ possible mappings).
Further, are PAC multi-nodes actually redundant as the PAC is
satisfied if _zero_ or more nodes satisfy it, meaning that even if
there's no node present, the PAC would be satisfied anyway.  Finally,
is there a reasonable example where multi-nodes in the RHS make sense?

If I didn't state my question precise enough or if you need an
example, please let me know ;)

Best wishes, Sebastian
- -- 
Sebastian Gabmeyer
Business Informatics Group (BIG)
Vienna University of Technology

http://www.big.tuwien.ac.at/staff/sgabmeyer
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