Thanks both. I will then, for my own purposes, assume that the full-morphism semantics is always the intended one and “sanitise” partial mappings before using them for my purposes.
Sidenote: this has come up in the context of trying to shift application conditions along morphisms. Any ACs I produce will always have a full mapping to keep things easy.
Thanks,
Steffen
Dr. rer. nat. Steffen Zschaler AHEA
Senior Lecturer
King's College London
Department of Informatics
Visiting Scientist
The Francis Crick Institute
Email szschaler@xxxxxxx
Phone +44 (020) 7848 1513
WWW
www.steffen-zschaler.de
From: henshin-user-bounces@xxxxxxxxxxx <henshin-user-bounces@xxxxxxxxxxx>
On Behalf Of Daniel Strüber
Sent: 20 December 2019 09:57
To: henshin-user@xxxxxxxxxxx
Subject: Re: [henshin-user] NestedConditions
Hi Stefan,
thanks for looking into this, these are some valuable insights.
Point 1 shows that it's been a while since I tried this out myself ;-) I can reproduce your observation: The "border elements only" NAC is interpreted with a "full LHS replicated" semantics, that is, objects already bound by the LHS are not considered for
matching the NAC.
Points 2 and 3 clarify that full LHS replication is indeed the default behavior in the graphical editor, but that there are some bugs related to synchronization, the graphical editor's number-one source of errors. Thanks also for offering to have your student
look into this.
To wrap up, it seems like the interpreter (in contrast to my previous statement) indeed uses the standard semantics, and, to achieve that, shows some tolerance w.r.t. incomplete specifications of the morphism. An alternative semantics with actual partial
morphisms might be desirable for some cases, but won't become our most urgent feature request, as our lives are interesting enough.
Best regards,
Daniel
On 12/20/2019 10:10 AM, S. John wrote:
Three things to note here:
1. In theory I would have said yes. In practice, however, I don't observe a difference running a rule with the whole replication vs. replicating only the border element (see attached rules). Did I miss something?
2. I don't observe the partial mapping being the standard behavior. For me it usually maps the Whole LHS to the NAC, but:
3. There seems to be a flaw in the graphical editor where the order in which you create the forbid and preserve parts of a rule influences how many elements are replicated and mapped.
Preserve elements which are added to a rule after a NAC has been created (by changing the action of a node to forbid) will not be replicated to that NAC. If you want to add existing preserve nodes to a NAC a workaround can be to change the desired forbid nodes
to preserve and back to forbid again.
In the past, I already observed strange behavior in not being able to create edges between forbid and preserve nodes sometimes but didn't search for the reason.
Now that I know the problem, I will assign my Henshin-Bugfix-Student to it. No guarantees on how long this will take, though. ;)
Stefan
On 19.12.2019 15:06, Zschaler, Steffen wrote:
Just to make sure I understand this correctly:
* When only the border elements are replicated in the NAC (here: the
:A node), the NAC looks like this:
* B -> A (where A has a mapping from the LHS)
*
Wouldn’t that mean the rule can simply never be matched (because there would, by definition always be a B to be matched for the NAC)?
Steffen
Dr. rer. nat. Steffen Zschaler AHEA
Senior Lecturer
King's College London
Department of Informatics
Visiting Scientist
The Francis Crick Institute
Email szschaler@xxxxxxx
Phone +44 (020) 7848 1513
WWW
www.steffen-zschaler.de
*From:*henshin-user-bounces@xxxxxxxxxxx
<henshin-user-bounces@xxxxxxxxxxx> *On Behalf Of *Daniel Strüber
*Sent:* 19 December 2019 13:26
*To:* henshin-user@xxxxxxxxxxx
*Subject:* Re: [henshin-user] NestedConditions
Consider a rule (using the integrated syntax:)
[forbid :B] ---> [preserve :A] <---- [preserve :B] <----- [create :C]
When only the border elements are replicated in the NAC (here: the :A node), the NAC looks like this:
B -> A (where A has a mapping from the LHS)
When the full LHS is replicated, the NAC looks like this:
B -> A <- B (where A, the right-hand B, and their common edge have mappings from the LHS)
Using the first NAC, the forbid node can be matched to all :B objects from the input model, including one which was bound to the preserve :B node while matching the LHS.
Using the second NAC, the forbid node cannot be matched to a :B object which was already bound by LHS :B node.
Best regards,
Daniel
On 12/19/2019 2:15 PM, Zschaler, Steffen wrote:
Thanks, Daniel. You seem to imply that there is a semantic
difference between the three forms. Could you explain?
Thanks,
Steffen
Dr. rer. nat. Steffen Zschaler AHEA
Senior Lecturer
King's College London
Department of Informatics
Visiting Scientist
The Francis Crick Institute
Email szschaler@xxxxxxx
<mailto:szschaler@xxxxxxx>
Phone +44 (020) 7848 1513
WWW
www.steffen-zschaler.de
<https://eur03.safelinks.protection.outlook.com/?url="">
*From:*henshin-user-bounces@xxxxxxxxxxx
<mailto:henshin-user-bounces@xxxxxxxxxxx>
<henshin-user-bounces@xxxxxxxxxxx>
<mailto:henshin-user-bounces@xxxxxxxxxxx> *On Behalf Of *Daniel Strüber
*Sent:* 19 December 2019 13:13
*To:* henshin-user@xxxxxxxxxxx
<mailto:henshin-user@xxxxxxxxxxx>
*Subject:* Re: [henshin-user] NestedConditions
Hi Steffen,
Henshin allows the morphism between the host graph and the
application condition graph to be a partial morphism. Consequently,
all three cases you mention (only nodes replicated, only border
nodes replicated, full LHS replicated) would specify different
application conditions for the same rule.
While this design decision has its awkward sides (especially the
representation in the graphical editor), I encountered some
situations before where it was desirable, as it allowed to precisely
specify an intended behavior.
I'm actually surprised by the fact that the graphical editor
defaults to the "node only" case -- I would have expected "full LHS
replicated" as the default. However, in most cases, the resulting
behavior will be identical. The only exceptions seem to arise in the
(exceptionally rare) case where there are multiple references of the
same type between the same two objects.
Best regards,
Daniel
On 12/19/2019 11:32 AM, Zschaler, Steffen wrote:
Hi,
A rather technical question about *NestedCondition*s and their
/representation/ in a .henshin file. Do tell me to take this
somewhere else if that would be more appropriate.
I understand the theory behind application conditions: the
condition is a graph and a morphism into this graph from a host
graph. That is represented in Henshin by the ability to add a
“formula” to a graph, where this formula can be a
*NestedCondition*, which itself again contains a graph and a set
of mapping. The containing graph is the host graph, the graph in
the *NestedCondition* is the application-condition graph, and
the mappings capture the morphism. So far so clear.
Except that’s not how it seems to work in practice: if you look
at the attached file, produced by the standard graphical editor,
you will see that only the /nodes/ from the host graph have been
replicated in the application-condition, but the /edges/
haven’t. In other examples, I have seen cases where only the
border nodes had been replicated. In any case, the mappings
clearly aren’t a morphism as they do not fully cover the host graph.
Are all of these formats indeed acceptable? If so, is there a
regularised format that is used inside Henshin and, if so, can
this be reused outside of Henshin? Alternatively, are there
minimum expectations on how an application condition should be
encoded in a .henshin file? Is any of this documented anywhere?
Should it be?
Thanks,
Steffen
Dr. rer. nat. Steffen Zschaler AHEA
Senior Lecturer
King's College London
Department of Informatics
Visiting Scientist
The Francis Crick Institute
Email szschaler@xxxxxxx
<mailto:szschaler@xxxxxxx>
Phone +44 (020) 7848 1513
WWW
www.steffen-zschaler.de
<https://eur03.safelinks.protection.outlook.com/?url="">
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Chalmers | University of Gothenburg, Sweden
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