Re: [Boost-users] [statechart ] UML2.0 local transitions and history

From: Andreas Huber (ahd6974-spamgroupstrap_at_[hidden])
Date: 2006-05-01 14:57:01

Hi Tim

> It seems that the sequence of exit and entry actions invoked for a
> transition are modeled according to the UML 1.5 specification.

Right.

> In
> other words it models "external" transitions from the 2.0 spec. Is it
> possible,

It's certainly possible ...

> or are there any plans to extend it, to model the more
> useful local transitions from the 2.0 spec?

There weren't any plans until I read your post :-). It seems that any 
local transition can always be converted to an external transition or an 
in-state reaction. The only benefit I see is improved performance (one 
state exit & entry less) under IME rare circumstances. So, the question 
is: How often do you use such transitions?

> Tests with deep history produce a static assertion if you attempt to
> transition to history of a containing state. UML 2.0 explicitly
> permits this.

I disallowed such transitions because they don't seem to make sense and 
there was no indication that they are allowed under UML 1.5. IIUC, such 
a transition would simply leave & reenter the current state, right? If 
so, what good is history for when the same effect can be achieved by 
simply giving the state a normal transition to itself?

> Are there any plans to modify the library to permit
> this?

If there are compelling use cases I'd certainly add both features ASAP.

Thanks for the feedback!

Regards,

-- 
Andreas Huber
When replying by private email, please remove the words spam and trap
from the address shown in the header.