Towards an Aspect-oriented Language Module:Aspects for Petri Nets

Tim Molderez, Bart Meyers, Dirk Janssens and Hans Vangheluwe

AnsymoAntwerp Systems and Software Modelling

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Introduction Building a language from scratch is a large effort:

Construct languages by composing modules

Aspect-oriented versions of many

different languages

→What about an “aspect-oriented language module”?• Using the module will add aspect-oriented features to your language

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Introduction Initial step towards an AO language module:

Start with something completely different than

commonly used base languages (e.g. Java)

… Petri nets!• Non-deterministic, minimal and a different purpose

How do typical AOP features work for Petri nets?

Design the AOP extension in a modular fashion

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Running example

P5-P8: represent rooms of a building

«enter», «exit» stereotypes: entrances and exits

Invariant: There may never be more than 30 people inside at the same time.

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Running example

VisitorCounter aspect: Keeps track of how many people are in the building

WaitingLine aspect: Prevents access if the building is full

and directs these people to a waiting line

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AOPN extension overview

Base language (PN) Join point model

Pointcut languageAdvice language

Weaver Composition mechanism

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Join point model Whenever a transition is about to fire.

Not affected by non-determinism:• Petri net execution has already chosen/determined among all

enabled transitions which one will be fired.

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Weaver1. When a join point is reached, pause Petri net execution.

2. Find all matching pointcuts, given the current state.

3. Use the composition mechanism to arrange the matched

pointcuts in the right order.

4. Insert all corresponding advice into the Petri net, in the

composition order.

5. Resume Petri net execution.

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VisitorCounter aspect

Keeps track of the number of people in the building

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increaseOnEnter pointcut-advice pair

Tracks all people entering

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transition pointcut construct

Captures all instances of transitions by name or stereotype

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Introductions: Allow places to be shared across advice instances and aspects

Introduced places can be a singleton, or per transition

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Input-output place binding

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Advice insertion in 3 steps: What happens if increaseOnEnter matches on

T1

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Simple AspectJ-like precedence mechanism

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pertransition introduction: One waiting line per entrance

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tokens pointcut construct: If the building is

full

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Proceed transition: If multiple pointcuts match, insert

the next advice at the proceed transition

No proceed transition: To prevent a transition from firing

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Demo

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Conclusion Initial step towards an AO language module:

Aspect-oriented Petri nets

Future work• Study other base languages to refine concept of language module• Define the interactions between the module’s components• How does adding aspect affect Petri nets’ use for analysis• Petri nets suitable language to study interactions among aspects

Download this presentation at: http://tinyurl.com/dsal12aopn

Contact: tim.molderez@ua.ac.be, bart.meyers@ua.ac.be | http://ansymo.ua.ac.be

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Mapping to Petri nets

No advice

Never applies

increaseOnEnte

r

If building not full

decreaseOnEnte

r

Always applies

moveToWaitingLine

+ increaseOnEnter /

preventEntrance

If building full