EXPERT SYSTEMS WITH APPLICATIONS 34

2008 IEEE

69721033 陳郁婷

A formal modeling platform for composing web services

Outline

IntroductionPetri NetsSCMPExampleConclusion

Introduction

Service requesters regard most Web services as outsourced applications 不保證 connectivity and reliability 整合困難

The Web services technology stack still lacks a composition standard 互不相容

a composition must consider non-functional QoS issues more than functional QoS issues such as workflow reliability

Petri Nets-based Composing SCMP (Service Composition Modeling Platform)

Petri Nets

PN = (P, T, F, M, W) P : a set of places. T : a set of transitions that represents the set for

tasks, processes, activities, or events. F : a set of arcs used to represents flow paths M : an initial marking (M0, …… ,Mn) W : a set of arc weights denoting how many tokens

are consumed from a place by a transition

Web Service Petri Net

WSPN(Web Service Petri Net)WSPN = (P,T, F, Y, A)

P : a set of places →P = {p1,p2, . . . ,pn} T : a set of transitions →T = {t1,t2, . . . ,tn} F : a set of arcs → Y : a set of types →Y = {y1,y2, . . . ,yn}

BP : base place SIP : service input place SOP : service output place

A: P→ Y : association of places to types

WfMC

SCMP (Service Composition Modeling Platform)

A visual editing module defining a conceptual service composition model using

the Petri Nets-based mechanism.A script language translation module

translate a conceptual model into a preferred composition script language.

A workflow measurable module employs evaluation algorithms to validate

nonfunctional workflow properties of Web services compositions.

•service finderUniversal Description, Discovery and Integration (UDDI) business registry (namely, the UBR)

•description document loader mechanisms

•WSFL and BPEL4WS language transformation•translator employs XSLT and XPath • specify elements and their

relationships•可 link 到 workflow engines• load the composition scripts • Test the execution results

•translate :• conceptual services

composition ↓PNML (in XML)

• Safeness : • if it has no more then one

token of a Petri Nets• Coverability tree

algorithm•Deadlocked : • if no transitions are

enabled• transitive matrix

algorithm•Reachable : • if it can be generated by

a sequence of transition firings beginning at the initial marking

SCMP 截圖

Base WS flow

Example 1

使用者要求英文文章找尋中文文章翻譯成英文文章回傳結果給使用者

2.Factor building

1. visual editing

PNML code document

<place id = ‘‘i1’’><name><text>newsRequest</text></name></place> <place id = ‘‘o1’’><name><text>newsResponse</text></name></place> <place id = ‘‘i2’’><name><text>englishNews</text></name></place> <place id = ‘‘o2’’><name><text>translatedNews</text></name></place>

<transition id = ‘‘op1’’><name><text>ProcessSRL</text></name></transition>

<transition id = ‘‘op2’’><name><text>BabelFish</text></name></transition> <transition id = ‘‘t1’’><name><text>Sequence1</text></name></transition>

<arc id = ‘‘aiop1’’source = ’’i1’’ target = ‘‘op1’’> . . . </arc> <arc id = ‘‘aopo1’’source = ’’op1’’ target = ‘‘o1’’> . . . </arc> <arc id = ‘‘aiop2’’source = ’’i2’’target = ’’op2’’> . . . </arc> <arc id = ‘‘aopo2’’source = ’’op2’’target = ’’o2’’> . . . </arc> <arc id = ‘‘aot1’’source = ’’o1’’target = ’’t1’’> . . . </arc> <arc id = ‘‘ati1’’source = ’’t1’’target = ’’i2’’> . . . </arc>

Example 2

Lin 想借貸 50 萬

loanSerC

Conclusion

SCMP 不需要很多時間及技巧就能建構一個健全的 service

composition GUI 介面加快建構速度

未來 讓 SCMP 能連線到適當的 workflow engines 加入更多的 Petri Nets mathematical algorithms 或

formal analysis methods 來確認各種的 QoS properties.

Coverability tree

Coverability tree

JARP Peri Net Analyzer

Web service binding layer

WSCSs translation layer