T owards An Open Trace-based Mechanism position paper Authors: - - PowerPoint PPT Presentation

T

• wards An Open

Trace-based Mechanism

position paper

Authors: Paul Leger and Éric Tanter

Department of Computer Science (DCC) University of Chile

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A Trace-based Mechanism (TM) in a nutshell

A TM observes the execution of the software and executes a piece of code when this TM matches a specified sequence of events.

d d b f a Trace of execution

TM needs to match

b a b

The piece

• f code of TM

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Matching a sequence

a y b x b Trace of execution

TM needs to match

b a b

Is it a valid match?

It depends because different TMs have different semantics to define sequences

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Strategies for multiple matching

a y b x b Trace of execution

TM needs to match

b a b

Is there another match?

It depends because different TMs have different strategies for multiple matching

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The life cycle of sequences

TM needs to match

a b x y

Except

a y b x b Trace of execution b

Most TMs cannot control the life cycle of sequences

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Current TMs

Tracematch [Allan+@OOPSLA05], Alpha [Herzeel+@ILC07], Halo [Ostermann+@ECOOP05], PTQL [Goldsmith+@OOPSLA05], ... Specific and non-configurable features What happens if developers have specific needs?

Is it a solution to “code around”?

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Towards an Open TM (OTM) model

We identified three points of openness in a TM:

• The multiple matching strategy. For example:
• To match several sequences at the same time
• To match only one sequence at the same time
• ...
• The life cycle of the sequences. For example:
• To remove all sequences if some condition is satisfied (except example)
• To match all sequences if some condition is satisfied
• ...
• Sequences definition. For example:
• Regular expressions
• Context-free languages
• ...

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Sequence

OTM model

seq a b Env

b Env' Trace of execution a b

TM needs to match

a b MATCH Env''

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Nondeterminism support

||

a b a c

• Some operators to define sequences, like

OR, are not deterministic. For example:

• If happens, then two different histories of

the matching of the same sequence are generated.

a

||

b a c

||

a b c

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The AnyOrder operator matches several sequences in any order.

Example: The AnyOrder Operator

, ,

a b a d a b a b a b a a b s d a b a b a b

, ,

a b a d a b a b a b x a b c d a b a b a b a c a b d x

Trace of execution

b TM needs to match

2 1 3

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Towards an Open TM (OTM) model

We identified three points of openness in a TM:

• The multiple matching strategy. For example:
• To match several sequences at the same time
• To match only one sequence at the same time
• ...
• The life cycle of the sequences. For example:
• To remove all sequences if some condition is satisfied (except example)
• To match all sequences if some condition is satisfied
• ...
• Sequences definition. For example:
• Regular expressions
• Context-free languages
• ...

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Extending OTM

• We add a multiplexer entity to define

strategies for multiple matching.

• We add a sequence controller entity to

control the life cycle of the sequences.

Multiplexer Sequence 2 Sequence 1 Sequence controller Sequence 1 Sequence 2

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Conclusions

• We explored the points where a TM can be opened:

– Sequences definition – Multiple matching strategies – Life cycle of sequences – Any others?

• We designed an open TM model, taking into account

these points

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Thank you!

Future work:

• Extend AspectScript[1] to support the OTM model.

[1] AspectScript: Expressive Aspects for the Web. Wednesday, March 17th at 12:30

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The class diagram of our open TM

Sequence SequenceController Multiplexer

Multiple TraceMatch

. . .

Developers can build strategies for multiple matching.

Except

Developers can build strategies to control life cycle of sequences

1 .. * 1

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A Open TM

Sequence 1 seq sa sb Env sb Env1 Sequence 2 sb Env2 MATCH Env1' a a b Trace of Execution Sequence Manager Multiplexer MATCH Env2'

TM needs to match

a b