EDA (Event-driven Architecture)

Just as many IT shops are starting to get their arms around the service-oriented architecture (SOA) approach now that Web services standards are emerging, there's already a “next big thing” on the development horizon, according to Gartner Inc.

Four years from now, “mere mortals” will begin to adopt an event-driven architecture (EDA) for the sort of complex event processing that has been attempted only by software gurus building operating systems or systems management tools, and sophisticated developers at financial institutions, predicted Roy Schulte, an analyst at Gartner.

Fortunately for IT shops, the EDA approach is complementary to SOA, which forward-thinking IT shops are starting to employ in greater numbers as they forge ahead with Web services. Taking an SOA-based approach, developers build an application by assembling “services,” or software components that define reusable business functions.

One of the main advantages of the SOA approach is that by building standards-based interfaces between components, developers can incrementally construct applications and swap out, reuse and modify components without having to concern themselves with their inner workings. Those who build Web services typically describe the interfaces using the Web Services Definition Language and send XML-based messages between components using SOAP over HTTP.

But connecting services occurs in a linear, predictable sequence, whereas an event-driven architecture allows for multiple, less predictable, asynchronous events to happen in parallel and trigger a single action.

Simple event-driven processing has been in common use for at least 10 years with technology such as IBM's message-oriented middleware and message-driven Enterprise JavaBeans.

But Schulte predicted that complex event processing (CEP) will start to become mainstream in 2007, as application developers and systems and business analysts strive to do more business in real time. Paving the way for the trend will be faster networks, the arrival of general-purpose event management software tools and the emergence of standards for event processing beginning in 2005.

David Luckham, a professor of electrical engineering at Stanford University and author of a book on CEP, The Power of Events, said the goal of CEP is rather simple: delivering understandable information about what's happening in IT systems. That information, in turn, can be used for a variety of purposes, such as detecting unusual activity, improving security and recognizing advantageous scenarios in CRM and supply-chain systems.

“The events in IT systems contain untapped information. CEP lets you extract it and use it in ways you want to,” he said.

Luckham predicted that CEP will start creeping into Web services, middleware and application servers in 2005. By 2008, he foresees the emergence of CEP standards, languages and complex event-pattern search engines. Ubiquity of CEP will come in 2012, he forecasted.

To prepare for EDA, Schulte advised companies to look at their application requirements to see if there are places where they could do simple event processing instead of SOA to design part of an application. Leading-edge companies should also look to implement complex event processing for applications that bring a competitive advantage.

參考譯文

EDA(事件驅(qū)動(dòng)架構(gòu))

據(jù) Gartner公司的分析，隨著Web Services標(biāo)準(zhǔn)的出現(xiàn)而更多的公司開始擁抱面向服務(wù)架構(gòu)(SOA)，在開發(fā)的地平線上已經(jīng)出現(xiàn)了“下一個(gè)大家伙”。

Garnter公司的分析師Roy Schulte預(yù)測，今后四年中，“小小的死東西”也將采納EDA用于那些今天只有開發(fā)操作系統(tǒng)或系統(tǒng)管理工具的軟件巨頭們和金融機(jī)構(gòu)中的資深開發(fā)者才敢嘗試的復(fù)雜事件處理。

對于 IT部門來說幸運(yùn)的是，EDA方法與SOA是互補(bǔ)的，隨著具有前瞻思想的IT部門伴隨Web Services向前進(jìn)時(shí)，他們開始更多地采用此方法。采用基于SOA的方法，開發(fā)者通過將那些定義可重復(fù)用業(yè)務(wù)功能的“服務(wù)”或軟件部件組裝起來，就能構(gòu)建應(yīng)用程序。

SOA方法的主要優(yōu)點(diǎn)之一，通過構(gòu)建部件之間基于標(biāo)準(zhǔn)的接口，開發(fā)者就能不斷編制應(yīng)用程序，在無需關(guān)心部件內(nèi)部工作的情況下交換、重復(fù)使用和修改部件。那些構(gòu)建Web Services的開發(fā)者通常用Web Services定義語言描述接口，以及在部件之間利用在HTTP上的SOAP(簡單對象接入?yún)f(xié)議)發(fā)送基于XML的消息。

但是連接服務(wù)是以線性的可預(yù)測順序發(fā)生的，而事件驅(qū)動(dòng)架構(gòu)允許多個(gè)不大可預(yù)測的異步事件并行地發(fā)生和觸發(fā)單一動(dòng)作。

利用諸如 IBM面向消息中間件和消息驅(qū)動(dòng)Enterprise JavaBeans等技術(shù)，簡單的事件驅(qū)動(dòng)處理已經(jīng)廣泛使用至少有10年。

但是 Schulte預(yù)測，隨著應(yīng)用開發(fā)者和系統(tǒng)與業(yè)務(wù)分析師努力爭取實(shí)時(shí)地做更多業(yè)務(wù)，復(fù)雜事件處理(CEP)到2007年將開始成為主流。更快的網(wǎng)絡(luò)、通用事件管理軟件工具的到來、以及2005年開始出現(xiàn)事件處理標(biāo)準(zhǔn)，為此趨勢鋪平了道路。

斯丹福大學(xué)電氣工程教授和有關(guān) CEP的《The Power of Events》一書的作者David Luchham稱，CEP的目標(biāo)是相當(dāng)簡單的：遞交有關(guān)IT系統(tǒng)中正在發(fā)生著什么的信息。該信息反過來又能用于各種不同的目的，如檢測不尋常的活動(dòng)、改進(jìn)安全、以及重組CRM(客戶關(guān)系管理)和供應(yīng)鏈系統(tǒng)中優(yōu)勢的情景。

他說： “IT系統(tǒng)中包含了未觸動(dòng)的信息。CEP讓你將它們提取出來，依你想要用的方式使用它們。”

Luchham預(yù)測，CEP將在2005年進(jìn)入Web Services、中間件和應(yīng)用服務(wù)器。到2008年，他預(yù)言將出現(xiàn)CEP的標(biāo)準(zhǔn)、語言和復(fù)雜事件模式搜索引擎。他預(yù)計(jì)，到2012年CEP將普及。

為了迎接 EDA，Schulte建議各公司檢查一下他們的應(yīng)用要求，看看是否能用簡單的事件處理代替SOA，以設(shè)計(jì)應(yīng)用程序的一部分。公司也應(yīng)該看看為能帶來競爭優(yōu)勢的應(yīng)用程序?qū)崿F(xiàn)復(fù)雜的事件處理。