軟件體系結(jié)構(gòu)—虛擬機(jī)風(fēng)格軟件體系結(jié)構(gòu)課程組本節(jié)內(nèi)容虛擬機(jī)風(fēng)格1解釋器風(fēng)格22規(guī)則引擎34課程總結(jié)虛擬機(jī)風(fēng)格Interpreters（解釋器）SimulatefunctionalitywhichisnotnativetothehardwareRule-basedsystems（規(guī)則系統(tǒng)）SpecializationofaninterpreterOtherSyntacticshellsCommandlanguageprocessors解釋器風(fēng)格Problem:

Thispatternissuitableforapplicationsinwhichthemostappropriatelanguageormachineforexecutingthesolutionisnotdirectlyavailable.Thepatternisalsosuitableforapplicationsinwhichthecoreproblemisdefininganotationforexpressingsolutions,forexampleasscripts.Interpretersaresometimesusedinchains,translatingfromthedesiredlanguage/machinetoanavailablelanguage/machineinaseriesofstages.Context:

Theinterpreterwillmostoftenbedesignedtobridgethegapbetweenthedesiredmachineorlanguageandsome(possiblyvirtual)machineorlanguagealreadysupportedbytheexecutionenvironment.解釋器風(fēng)格Solution:Systemmodel:virtualmachineComponents:onestatemachine(theexecutionengine)andthreememories(currentstateofexecutionengine,programbeinginterpreted,currentstateofprogrambeinginterpreted)Connectors:dataaccessandprocedurecallControlstructure:usuallystate-transitionforexecutionengine;inputdrivenforselectionofwhattointerpretSignificantVariants:Expertsystemsareoftenimplementedasinterpretersforthecollectionsofrules,orproductions,thatrepresenttheexpertise.Becausetheproductionsrequireacomplexselectionrule,specializedformsofinterpretershaveevolved.解釋器風(fēng)格解釋器風(fēng)格：優(yōu)勢(shì)Functionality:Cansimulatenon-nativefunctionalityTesting:Cansimulate“disaster”modes(e.g.forsafety-criticalapplications)Flexibility:Verygeneral-purposetool解釋器風(fēng)格：劣勢(shì)Efficiency:Much,muchslowerthanhardwareMuchslowerthancompiledsystemTesting:Additionallayerofsoftwaretobeverified解釋器風(fēng)格：用途解釋型語言VB、Javascript、VBScript、HTML、Java字節(jié)碼、Matlab腳本、配置文件通信協(xié)議用戶輸入游戲中的組合按鍵規(guī)則系統(tǒng)風(fēng)格規(guī)則系統(tǒng)特征Codetobeexecuted(knowledgebase)Interpretationengine(ruleinterpreter)Controlstateofinterpreter(rule/dataselection)Currentstateofthecode(workingmemory)復(fù)雜規(guī)則系統(tǒng)示例規(guī)則系統(tǒng)的抽象黑板系統(tǒng)與規(guī)則系統(tǒng)的相似性一個(gè)實(shí)際的規(guī)則引擎：DroolsDrools是Redhat公司JBoss業(yè)務(wù)邏輯智能模塊/drools/Drools是處理規(guī)則的專家系統(tǒng)一個(gè)實(shí)際的規(guī)則引擎：Drools聲明式編程規(guī)則引擎允許你說“做什么”，而不是“怎樣去做”規(guī)則系統(tǒng)能解決非常困難的難題邏輯和數(shù)據(jù)分離快捷和靈活知識(shí)集中化工具集成良好的解釋機(jī)制易于理解的規(guī)則一個(gè)例子產(chǎn)生背景系統(tǒng)龐大，業(yè)務(wù)復(fù)雜業(yè)務(wù)規(guī)則經(jīng)常改變24小時(shí)服務(wù)業(yè)務(wù)統(tǒng)一管理降低系統(tǒng)維護(hù)升級(jí)成本產(chǎn)生式規(guī)則引擎許多產(chǎn)品規(guī)則系統(tǒng)的大腦實(shí)際上就是一個(gè)推理引擎，用于匹配事實(shí)（Fact）和規(guī)則（Rule）當(dāng)匹配被找到，規(guī)則對(duì)應(yīng)的動(dòng)作（Action）會(huì)被觸發(fā)（Fire）動(dòng)作經(jīng)常會(huì)改變事實(shí)的狀態(tài)，或者在應(yīng)用上執(zhí)行一些“外部”動(dòng)作RETE網(wǎng)絡(luò)節(jié)點(diǎn)簡(jiǎn)單的RETE網(wǎng)絡(luò)Drools體系結(jié)構(gòu)Drools體系結(jié)構(gòu)與經(jīng)典的規(guī)則引擎對(duì)比虛擬機(jī)風(fēng)格總結(jié)Interpreters（解釋器）Simulatefunctionalitywhichisnotnativetotheha