On the Semantics of Matching Trace Monitoring Patterns

/ 26Hong,Shin @ PSWLAB

On the Semantics of Matching Trace Monitoring Patterns

P Avgustinov, J Tibble, O Moor(Programming Tool Group, Oxford, UK)

June 29th, 2007Presented by Shin Hong at PSWLAB, KAIST

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1On the Semantics of Matching Trace Monitoring Patterns Hong,Shin@PSWLAB


Contents

• Introduction

• Exact-matching Semantics

• Skipping Semantics

• The equivalence of two semantics

• Conclusion

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On the Semantics of Matching Trace Monitoring Patterns 2


Introduction (1/2)• A trace monitor observes a base

program’s execution and check whether it is valid or not.

• A trace specification specifies a valid trace pattern.

• There is wide variety of the specification languages for describing trace specificationsRegular expression, context-free language, temporal

logic, query language, etc.

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Introduction (2/2)• The styles of the specification

languages’ semantics are different– Exact-matching semantics– Skipping semantics

for example, AB meansin exact-matching, A and next B.

in skipping, A and eventually B.

• Define a small skipping language with the skipping semantics explore its expressiveness.

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Contents• Introduction• Exact-matching Semantics

- Regular expression in tracematches, Lem

• Skipping Semantics- A small skipping language, Lskip

• The equivalence of two semantics- L(Lskip ) ⊂ L(Lem)

- L(Lem) ⊇L (Lskip with modified Kleene star)

• Conclusion

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Exact-matching Semantics (1/3)• Many systems with an AOP background

employ exact-matching semantics.

• Every symbol in an input word must be accounted for by the pattern.

• Tracematches employs this semantics.

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Exact-matching Semantics (2/3)tracematch(Observer o, Subject s) { sym createObserver after: pcCreateObserver(o,s) ; sym updateSubejct after: pcUpdateSubject(s) ; sym removeObserver after: pcRemoveObserver(o,s); createObserver updateSubject+ {o.subjectUpdate();}}---------------------------------------------------------------Observer {… void addSubject(Subject s) { … <pcCreateObserver>} void eraseSubject(Subject s) { … <pcRemoveObserver>} void subjectUpdate(Subject s) {… }…}Subject {… void changeValue() { … <pcUpdateSubject>} …}----------------------------------------------------------------------

createObserver updateSubject updateSubject removeObserver

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Exact-matching Semantics (3/3)• Syntax of Tracematches Exact-matching Language

Lem

pattern := term | seqPattern ‘|’ pattern

term := simplePattern | simplePattern term

|

simplePattern ‘*’

simplePattern := symbol | ‘(‘ pattern ’)’

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Skipping Semantics (1/6)• Many systems with an RV background

employ skipping semantics.

• The languages with skipping semantics specify events that happen one after the other, with any events allowed in between.

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Skipping Semantics (2/6)ReqSpec Sample

import event a, w, x, y, z ;

import condition night ;

var happenA, count ;

alarm 3a = a when happenA==3 ;

a -> { happenA’ = happenA + 1 ; }

b -> { happenA’ = 0 ; }

property 10wxyz = count < 10 ;

event wxyz = (y||z when [w,x)) ||

(z when [w, end([x,y)))) when night

wxyz -> {count’ = count+1;}

End

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Skipping Semantics (3/6)

A simple skipping language Lskip

– Similar with Lem

– Explicit negation

~A : any numbers of symbols that are not

A.

– Does not have Kleene star operator

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Skipping Semantics (4/6)• For example

AB ∈ L(AB + BC)ABB ∈ L(A B ~C B)ACABB ∈ L(A B ~C B)ACABCB ∉ L(A B ~C B)

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• Syntax of patterns in Lskip

pattern := fencedTerm | fancedTerm ‘|’ pattern

fencedTerm := simplePattern|

simplePattern fencedTerm |

simplePattern ‘~’ symbolSet fencedTerm

simplePattern := symbol | ‘(‘ pattern ‘)’

symbolSet := symbol | ‘(‘symbol‘|’symbolSet‘)’

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L(Lskip) ∋ A (B | C) A

L(Lskip) ∋ A ~(B | C) A

L(Lskip) ∌ A ~B ~C A

L(Lskip) ∌ A ~(B C) A

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Contents• Introduction• Exact-matching Semantics

- Regular expression in tracematches, Lem

• Skipping Semantics- A small skipping language, Lskip

• The equivalence of two semantics- L(Lskip ) ⊂ L(Lem)

- L(Lem) ⊇L (Lskip with modified Kleene star)

• Conclusion

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The equivalence of two semantics(1/5)• Syntax-directed translation from Lskip to Lem

Let α ⊆ Σ

[fencedTerm | pattern] [fencedTerm]|[pattern]

[simplePattern fencedTerm]

[simplePattern] Σ* [fencedTerm]

[simplePattern ~α fencedTerm]

[simplePattern] (Σ\α)* [fencedTerm]

[symbol] symbol

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The equivalence of two semantics(2/5)Σ = {A, B, C}

ABskip A(A|B|C)*Bem

A~BAskip A(A|C)*Aem

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The equivalence of two semantics(3/5)• Translation from a fragment of Lem to

Lskip

Let α⊆ Σ

[term | pattern] [term] | [pattern]

[simplePattern term][simplePattern] ~Σ [term]

[simplePattern α* term]

[simplePattern] ~(Σ\α)

[term]

[symbol] symbol23年 4月 21日



The equivalence of two semantics(4/5)• Skipping Language with modified Kleene closure

t@α ≡ t | t ~α t@α

prohibiting all events in α between repetitions of t

<Lskip Lem >

[term@α] ([term] (Σ\α)*)* [term]<Lem Lskip >

[term+] [term]@Σ

[term term*] [term]|[term]@Σ

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The equivalence of two semantics(5/5)A(BC)*em

( A | A(B ~Σ C)@Σ )skip

( A| A((B {}* C){}*)*)em

(A | A(B C)*)em

A | A(BC)* em A(BC)*em

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Conclusion-A skipping language with modified Kleene

closure and exact-matching language have the same expressive power.

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Conclusion

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References[1] On the Semantics of Matching Trace

Monitoring Patterns, Oege de Moor et al[2] Liveness Checking as Safety Checking to

Find Shortest Counterexamples to Linear Time Properties, Viktor Schuppan

[3] Adding Trace Matching with Free Variables to AspectJ, Chris Allan et al

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On the Semantics of Matching Trace Monitoring Patterns