Re: [henshin-dev] Difference between require and forbid?

[Christian Krause <henshin.ck@xxxxxxxxx>]

Hi Jens,

the difference between <<require>> and <<preserve>>-actions is exactly as you said: <<preserve>>-nodes are part of the matches, whereas for <<require>>-nodes their existence is checked, but they are not part of the match. Therefore, in the movies example, <<require>>-nodes are a means to avoid multiple matches for the same pair of actors. This means also that you cannot modify any properties of <<require>>-nodes, e.g., you cannot change attribute values or delete their edges (because they will not be part of the match).

Hope this helps.

Cheers,

Christian

2014-03-25 18:06 GMT+01:00 Jens Bürger <jens.buerger@xxxxxxxxxxxxxxxxx>:

Hello everyone,

what is the exact difference between the require and forbid-action?

Regarding the movies example of
http://www.ckrause.org/2013/12/path-constraints-in-henshin.html

the matching seems more restrictive in a way that not every permutation of three movies generates a separate match, but is there a place where this is made more clear?

The Henshin page of the Henshin wiki doesn't go into detail here either, because it even says
"Regarding semantics, PACs could be also specified using «preserve»":

http://wiki.eclipse.org/Henshin_Graphical_Editor


Thanks in advance,

Jens
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