[
https://issues.apache.org/jira/browse/SCXML-211?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Ate Douma updated SCXML-211:
----------------------------
Description:
While testing the SCXML specification using the [IRP Plan tests|
http://www.w3.org/Voice/2013/scxml-irp/] I discovered a bug in the current
specification addDescendantStatesToEnter algorithm:
[http://www.w3.org/TR/2014/WD-scxml-20140529/#addDescendantStatesToEnter]
I've already send a notice about this bug to the SCXML specification mailing
list, see: [http://lists.w3.org/Archives/Public/www-voice/2014OctDec/0000.html]
which I'm copying verbatim below:
{quote}
Hi there,
I think I detected a bug in the addDescendantStatesToEnter algorithm in the
specification concerning *when* to invoke the addAncestorsStatesToEnter.
Currently the algorithm defines the following logic for a compound state, after
having added it to the statesForDefaultEntry:
{noformat}
for s in getEffectiveTargetStates(state.initial.transition):
addDescendantStatesToEnter(s,statesToEnter,statesForDefaultEntry,
defaultHistoryContent)
addAncestorStatesToEnter(s, state, statesToEnter,
statesForDefaultEntry, defaultHistoryContent)
{noformat}
If not first for all effective target states addDescendantStatesToEnter is
executed, the addAncestorStatesToEnter might,
when in involves an ancestor parallel with nested compound states of which one
also happens to be one of the effective
desendant target *but not yet resolved*, end up initializing a different
(default) sibling child of such a compound state.
End result: an invalid configuration with a compound state having multiple
active child states.
I detected this issue when testing irp test364, which indeed defines such a
SCXML document.
If the algorithm is implemented as currently defined in the specification,
you'll end up with both s11p121 and s11p122
being on the statesToEnter set (or s11p111 and s11p112, depending on the
processing order of the s1 initial targets).
In Apache Commons SCXML I've implemented a legal configuration check before
executing enterStates, and that fails on
this point for irp test364.
Maybe important to note is that if I disable the check, the test actually
passes, so maybe others might have this same
bug but going unnoticed?
Solving this bug however should be pretty trivial.
To ensure explicit descendant target states are recorded first, I just changed
the above logic to:
{noformat}
for s in getEffectiveTargetStates(state.initial.transition):
addDescendantStatesToEnter(s,statesToEnter,statesForDefaultEntry,
defaultHistoryContent)
for s in getEffectiveTargetStates(state.initial.transition):
addAncestorStatesToEnter(s, state, statesToEnter,
statesForDefaultEntry, defaultHistoryContent)
{noformat}
And I did the same for the two similar/same for loops in the handling for
history states in addDescendantStatesToEnter
where likewise both descendant and ancestors states to enter are resolved
within a single loop.
Note: the description of addDescendantStatesToEnter actually does seem to say
it more correctly where it breaks these
two separate 'steps' down in two separate sentences:
{noformat}
Then if state is a compound state, add state to statesForDefaultEntry and
recursively call addStatesToEnter on its
default initial state(s).
Then, since the default initial states may not be children of 'state', add
any ancestors between the default
initial states and 'state'.
{noformat}
The above description at least gives the right direction how this should be
implemented, namely as separate consecutive steps,
but not 'optimized' into a single loop as currently done.
Confusingly and incorrectly though this description names the
"addDescendantStatesToEnter" routine "addStatesToEnter".
It probably would be good to correct that as well.
Kind regards,
Ate Douma
{quote}
was:
While testing the SCXML specification using the [IRP Plan tests|
http://www.w3.org/Voice/2013/scxml-irp/] I discovered a bug in the current
specification addDescendantStatesToEnter algorithm:
[http://www.w3.org/TR/2014/WD-scxml-20140529/#addDescendantStatesToEnter]
I've already send a notice about this bug to the SCXML specification mailing
list, see: [http://lists.w3.org/Archives/Public/www-voice/2014OctDec/0000.html]
which I'm copying verbatim below:
{quote}
Hi there,
I think I detected a bug in the addDescendantStatesToEnter algorithm in the
specification concerning *when* to invoke the addAncestorsStatesToEnter.
Currently the algorithm defines the following logic for a compound state,
after having added it to the statesForDefaultEntry:
for s in getEffectiveTargetStates(state.initial.transition):
addDescendantStatesToEnter(s,statesToEnter,statesForDefaultEntry,
defaultHistoryContent)
addAncestorStatesToEnter(s, state, statesToEnter,
statesForDefaultEntry, defaultHistoryContent)
If not first for all effective target states addDescendantStatesToEnter is
executed, the addAncestorStatesToEnter might,
when in involves an ancestor parallel with nested compound states of which one
also happens to be one of the effective
desendant target *but not yet resolved*, end up initializing a different
(default) sibling child of such a compound state.
End result: an invalid configuration with a compound state having multiple
active child states.
I detected this issue when testing irp test364, which indeed defines such a
SCXML document.
If the algorithm is implemented as currently defined in the specification,
you'll end up with both s11p121 and s11p122
being on the statesToEnter set (or s11p111 and s11p112, depending on the
processing order of the s1 initial targets).
In Apache Commons SCXML I've implemented a legal configuration check before
executing enterStates, and that fails on
this point for irp test364.
Maybe important to note is that if I disable the check, the test actually
passes, so maybe others might have this same
bug but going unnoticed?
Solving this bug however should be pretty trivial.
To ensure explicit descendant target states are recorded first, I just changed
the above logic to:
for s in getEffectiveTargetStates(state.initial.transition):
addDescendantStatesToEnter(s,statesToEnter,statesForDefaultEntry,
defaultHistoryContent)
for s in getEffectiveTargetStates(state.initial.transition):
addAncestorStatesToEnter(s, state, statesToEnter,
statesForDefaultEntry, defaultHistoryContent)
And I did the same for the two similar/same for loops in the handling for
history states in addDescendantStatesToEnter
where likewise both descendant and ancestors states to enter are resolved
within
a single loop.
Note: the description of addDescendantStatesToEnter actually does seem to say
it
more correctly where it breaks these
two separate 'steps' down in two separate sentences:
Then if state is a compound state, add state to statesForDefaultEntry and
recursively call addStatesToEnter on its
default initial state(s).
Then, since the default initial states may not be children of 'state', add
any ancestors between the default
initial states and 'state'.
The above description at least gives the right direction how this should be
implemented, namely as separate consecutive steps,
but not 'optimized' into a single loop as currently done.
Confusingly and incorrectly though this description names the
"addDescendantStatesToEnter" routine "addStatesToEnter".
It probably would be good to correct that as well.
Kind regards,
Ate Douma
{quote}
> Bug in current SCXML specification for addDescendantStatesToEnter algorithm
> can lead to illegal configurations
> --------------------------------------------------------------------------------------------------------------
>
> Key: SCXML-211
> URL: https://issues.apache.org/jira/browse/SCXML-211
> Project: Commons SCXML
> Issue Type: Bug
> Affects Versions: 2.0
> Reporter: Ate Douma
> Assignee: Ate Douma
> Fix For: 2.0
>
>
> While testing the SCXML specification using the [IRP Plan tests|
> http://www.w3.org/Voice/2013/scxml-irp/] I discovered a bug in the current
> specification addDescendantStatesToEnter algorithm:
> [http://www.w3.org/TR/2014/WD-scxml-20140529/#addDescendantStatesToEnter]
> I've already send a notice about this bug to the SCXML specification mailing
> list, see:
> [http://lists.w3.org/Archives/Public/www-voice/2014OctDec/0000.html]
> which I'm copying verbatim below:
> {quote}
> Hi there,
> I think I detected a bug in the addDescendantStatesToEnter algorithm in the
> specification concerning *when* to invoke the addAncestorsStatesToEnter.
> Currently the algorithm defines the following logic for a compound state,
> after having added it to the statesForDefaultEntry:
> {noformat}
> for s in getEffectiveTargetStates(state.initial.transition):
> addDescendantStatesToEnter(s,statesToEnter,statesForDefaultEntry,
> defaultHistoryContent)
> addAncestorStatesToEnter(s, state, statesToEnter,
> statesForDefaultEntry, defaultHistoryContent)
> {noformat}
> If not first for all effective target states addDescendantStatesToEnter is
> executed, the addAncestorStatesToEnter might,
> when in involves an ancestor parallel with nested compound states of which
> one also happens to be one of the effective
> desendant target *but not yet resolved*, end up initializing a different
> (default) sibling child of such a compound state.
> End result: an invalid configuration with a compound state having multiple
> active child states.
> I detected this issue when testing irp test364, which indeed defines such a
> SCXML document.
> If the algorithm is implemented as currently defined in the specification,
> you'll end up with both s11p121 and s11p122
> being on the statesToEnter set (or s11p111 and s11p112, depending on the
> processing order of the s1 initial targets).
> In Apache Commons SCXML I've implemented a legal configuration check before
> executing enterStates, and that fails on
> this point for irp test364.
> Maybe important to note is that if I disable the check, the test actually
> passes, so maybe others might have this same
> bug but going unnoticed?
> Solving this bug however should be pretty trivial.
> To ensure explicit descendant target states are recorded first, I just
> changed the above logic to:
> {noformat}
> for s in getEffectiveTargetStates(state.initial.transition):
> addDescendantStatesToEnter(s,statesToEnter,statesForDefaultEntry,
> defaultHistoryContent)
> for s in getEffectiveTargetStates(state.initial.transition):
> addAncestorStatesToEnter(s, state, statesToEnter,
> statesForDefaultEntry, defaultHistoryContent)
> {noformat}
> And I did the same for the two similar/same for loops in the handling for
> history states in addDescendantStatesToEnter
> where likewise both descendant and ancestors states to enter are resolved
> within a single loop.
> Note: the description of addDescendantStatesToEnter actually does seem to say
> it more correctly where it breaks these
> two separate 'steps' down in two separate sentences:
> {noformat}
> Then if state is a compound state, add state to statesForDefaultEntry
> and recursively call addStatesToEnter on its
> default initial state(s).
> Then, since the default initial states may not be children of 'state',
> add any ancestors between the default
> initial states and 'state'.
> {noformat}
> The above description at least gives the right direction how this should be
> implemented, namely as separate consecutive steps,
> but not 'optimized' into a single loop as currently done.
> Confusingly and incorrectly though this description names the
> "addDescendantStatesToEnter" routine "addStatesToEnter".
> It probably would be good to correct that as well.
> Kind regards,
> Ate Douma
> {quote}
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