|By Manoj Das, Alex Yiu, Khanderao Kand||
|October 1, 2007 07:15 AM EDT||
As most readers are probably aware, the Web Services-Business Process Execution Language (WS-BPEL) provides a broadly adopted process orchestration standard supported by many vendors today and used to define business processes that orchestrate services, systems, and people into end-to-end business processes and composite applications. However, in many ways BPEL's adoption has gotten ahead of the formal standardization process.
The BPEL4WS 1.1 specification was submitted to OASIS back in 2004 and after three years of work by one of the largest technical committees at OASIS, WS-BPEL 2.0 finally became an OASIS standard on April 12, 2007. While adoption of the BPEL language has not been gated by the 2.0 standard or the OASIS stamp of approval - there are thousands of successful BPEL projects and deployments today - the formal publication of the standard is an important milestone and will further accelerate BPEL's adoption and vendor support.
A lot has been already written about the new features in WS-BPEL 2.0 on various blogs, Web sites, and magazine articles, including the article "BPEL Grows Up" (http://soa.sys-con.com/read/346372.htm). In this article, we'll drill down into the next level of detail regarding the new features in WS-BPEL 2.0 using concrete examples wherever possible. Throughout this article, we abbreviate BPEL4WS 1.1 as BPEL 1.1 and WS-BPEL 2.0 as BPEL 2.0.
BPEL 2.0 Overview
At a high level BPEL is an XML language that provides a rich set of activities to describe an executable business process. The processes and activities can be synchronous or asynchronous, short-lived or long-running; BPEL provides a sophisticated language for defining the process flow, system interactions, data manipulation, exception handling, compensation rules, etc. First, we will briefly summarize the important features of the BPEL standard, explicitly calling out what is new or changed in BPEL 2.0: (Figure 1)
• Service interaction activities: A BPEL process is automatically a Web Service and receives inputs via <receive> or <pick> activities. A process can send back a synchronous Web Service response using <reply>. The <invoke> activity is available to invoke an external service, as described below, but also to respond asynchronously to a client.
• Event handling constructs: A process can get input requests at non-deterministic points during process execution with <eventHandlers> using <onEvent> for messages (new in BPEL - replaces <onMessage> from BPEL 1.1) or <onAlarm> for time-triggered events. <wait> can wait for a specified time or until a deadline is reached and <receive> can wait for events at pre-determined points in the process.
• Back-end system interactions: Interactions with external services are represented as <partnerLinks>. Asynchronous conversational interactions can be correlated using <correlationSet> or the WS-Addressing standard. A process maintains its state using <variables> that can be defined at global or local scope. BPEL 2.0 makes it easier to map process variables to WSDL message variables. It also provides the new <messageExchange> activity to distinguish instances of similar conversations (request/response pairs).
• Data manipulation activities: BPEL 2.0 adds a new simplified XPath notation ($variableName) replacing the getVariableData() function. Besides the existing <assign> activity to map data between variables, BPEL 2.0 provides a doXSLTransform() function to natively support XSL Transformations. A <validate> activity has been added for schema validations. These additions have already been time tested, having been implemented as extensions in vendor implementations of BPEL for quite some time now.
• Process structural flow related activities: BPEL includes basic structural activities similar to other workflow or programming languages for sequencing, iteration, and branching. BPEL 1.1 supported <sequence> for sequential execution, <flow> for parallel branches, and <while> for looping. BPEL 2.0 adds <if> / <else>, <repeatUntil> and <forEach> for richer flow control syntax. In particular, the new <forEach> construct now supports dynamic parallelism (executing N activities in parallel, when the value N is not known until execution time). This was not supported in BPEL 1.1 except through vendor extensions.
• Exception handling and recovery constructs: Exceptions, represented as faults, are propagated using <throw>, and BPEL 2.0 adds <rethrow> to provide more explicit control over exception management patterns. In <faultHandlers>, faults can be detected using <catch> and <catchAll>. A process can undo completed work through <compensationHandlers> and the <compensate> activity; BPEL 2.0 adds <compensateScope> to clarify the syntax of BPEL 1.1's overloading of the <compensate> activity. BPEL 2.0 also adds <terminationHandlers> to enable processes to specify the logic to be invoked just prior to the termination of a process.
• Extensibility: BPEL 2.0 adds <extensionAssignOperation> to extend the standard <assign> activity; it also provides <extensionActivity> to add new activity types. This is another area where the 2.0 standard now explicitly covers things that vendor implementations were already doing. BPEL 2.0 also now supports <import> and <documentation>.
Kitchens Online Use Case
To illustrate some of the BPEL features, we will use the example of Kitchens Online, a fictitious Internet-based kitchen-remodeling solution. Kitchens Online provides a Web site where customers can select appliances and cabinets and schedule delivery and installation. Kitchens Online doesn't carry any stock and sources the different components from various vendors; however it still wants to keep inventory information as up-to-date as possible. Complicating matters, the vendors Kitchens Online's suppliers don't always have automated inventory systems - in many instances, a person needs to check manually whether a given item is available. When a customer places an order, Kitchens Online tries to reserve all the needed components from its vendors. If it can't reserve a piece, the customer is notified and can then change or cancel the order.
An overview of Kitchens Online's business process is shown in Figure 2.
This example highlights the following advanced requirements:
- Dynamic Parallelism - handling of different components (line items) of an Order in parallel
- Change handling (out-of-band events) - a delivery schedule may change while an Order is in process
- Compensation - reversing credit card charges and releasing reserved inventory when a component is out-of-stock
Since this article is focused on the BPEL 2.0 standard, and BPEL is an XML language, we'll examine the BPEL "source code" in XML format. Of course most developers won't hand-code BPEL in the XML format - they'll use visual tools built on top of the standard. Several vendors and open source implementations of such tools exist, including some that enable developers to switch back and forth between a visual model of a BPEL process and the underlying BPEL source. Here we'll examine the underlying XML source, so get ready!
The Kitchens Online requirement to process the multiple items of an Order in parallel is a very common pattern. The <flow> activity introduced in BPEL 1.1 supported parallelism, but only when the number of parallel branches was known at design time. Here, an Order may have a variable number of items and therefore the number of parallel branches won't be known until runtime. What's needed is the equivalent of a typical programming language "for" loop where all the iterations of the loop are executed in parallel.
To address this pattern, BPEL 2.0 introduces the <forEach> activity. As the name indicates, this activity causes the enclosed scope to iterate between the <startCounterValue> and <finalCounterValue> inclusive (i.e., N+1 times, where N is the difference between the two). The <forEach> activity has an attribute parallel that when set to yes causes all the branches to be executed in parallel and a counterName attribute that specifies an integer variable that will hold the counter value for each particular iteration (1 for the first iteration in the example below, 2 for the second, etc.).
|Mike Edwards 10/05/07 06:55:06 AM EDT|
Good introduction to BPEL - and this begins to show how BPEL is better suited to doing some of the common business-process activities than some "conventional" languages.
It would be good to have a longer article discussing each aspect of the example application in more detail too.
In the 21st century, security on the Internet has become one of the most important issues. We hear more and more about cyber-attacks on the websites of large corporations, banks and even small businesses. When online we’re concerned not only for our own safety but also our privacy. We have to know that hackers usually start their preparation by investigating the private information of admins – the habits, interests, visited websites and so on. On the other hand, our own security is in danger bec...
Oct. 27, 2016 04:45 AM EDT Reads: 420
The Internet of Things (IoT), in all its myriad manifestations, has great potential. Much of that potential comes from the evolving data management and analytic (DMA) technologies and processes that allow us to gain insight from all of the IoT data that can be generated and gathered. This potential may never be met as those data sets are tied to specific industry verticals and single markets, with no clear way to use IoT data and sensor analytics to fulfill the hype being given the IoT today.
Oct. 27, 2016 04:45 AM EDT Reads: 2,867
Enterprises have been using both Big Data and virtualization for years. Until recently, however, most enterprises have not combined the two. Big Data's demands for higher levels of performance, the ability to control quality-of-service (QoS), and the ability to adhere to SLAs have kept it on bare metal, apart from the modern data center cloud. With recent technology innovations, we've seen the advantages of bare metal erode to such a degree that the enhanced flexibility and reduced costs that cl...
Oct. 27, 2016 04:30 AM EDT Reads: 450
Without lifecycle traceability and visibility across the tool chain, stakeholders from Planning-to-Ops have limited insight and answers to who, what, when, why and how across the DevOps lifecycle. This impacts the ability to deliver high quality software at the needed velocity to drive positive business outcomes. In his session at @DevOpsSummit 19th Cloud Expo, Eric Robertson, General Manager at CollabNet, will show how customers are able to achieve a level of transparency that enables everyon...
Oct. 27, 2016 04:00 AM EDT Reads: 1,361
Donna Yasay, President of HomeGrid Forum, today discussed with a panel of technology peers how certification programs are at the forefront of interoperability, and the answer for vendors looking to keep up with today's growing industry for smart home innovation. "To ensure multi-vendor interoperability, accredited industry certification programs should be used for every product to provide credibility and quality assurance for retail and carrier based customers looking to add ever increasing num...
Oct. 27, 2016 04:00 AM EDT Reads: 753
“Media Sponsor” of SYS-CON's 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. CloudBerry Backup is a leading cross-platform cloud backup and disaster recovery solution integrated with major public cloud services, such as Amazon Web Services, Microsoft Azure and Google Cloud Platform.
Oct. 27, 2016 03:45 AM EDT Reads: 1,506
In the next forty months – just over three years – businesses will undergo extraordinary changes. The exponential growth of digitization and machine learning will see a step function change in how businesses create value, satisfy customers, and outperform their competition. In the next forty months companies will take the actions that will see them get to the next level of the game called Capitalism. Or they won’t – game over. The winners of today and tomorrow think differently, follow different...
Oct. 27, 2016 03:45 AM EDT Reads: 1,111
@DevOpsSummit has been named the ‘Top DevOps Influencer' by iTrend. iTrend processes millions of conversations, tweets, interactions, news articles, press releases, blog posts - and extract meaning form them and analyzes mobile and desktop software platforms used to communicate, various metadata (such as geo location), and automation tools. In overall placement, @DevOpsSummit ranked as the number one ‘DevOps Influencer' followed by @CloudExpo at third, and @MicroservicesE at 24th.
Oct. 27, 2016 03:45 AM EDT Reads: 4,121
In his general session at 19th Cloud Expo, Manish Dixit, VP of Product and Engineering at Dice, will discuss how Dice leverages data insights and tools to help both tech professionals and recruiters better understand how skills relate to each other and which skills are in high demand using interactive visualizations and salary indicator tools to maximize earning potential. Manish Dixit is VP of Product and Engineering at Dice. As the leader of the Product, Engineering and Data Sciences team a...
Oct. 27, 2016 03:45 AM EDT Reads: 722
The security needs of IoT environments require a strong, proven approach to maintain security, trust and privacy in their ecosystem. Assurance and protection of device identity, secure data encryption and authentication are the key security challenges organizations are trying to address when integrating IoT devices. This holds true for IoT applications in a wide range of industries, for example, healthcare, consumer devices, and manufacturing. In his session at @ThingsExpo, Lancen LaChance, vic...
Oct. 27, 2016 03:30 AM EDT Reads: 3,830
Regulatory requirements exist to promote the controlled sharing of information, while protecting the privacy and/or security of the information. Regulations for each type of information have their own set of rules, policies, and guidelines. Cloud Service Providers (CSP) are faced with increasing demand for services at decreasing prices. Demonstrating and maintaining compliance with regulations is a nontrivial task and doing so against numerous sets of regulatory requirements can be daunting task...
Oct. 27, 2016 03:15 AM EDT Reads: 1,859
What are the successful IoT innovations from emerging markets? What are the unique challenges and opportunities from these markets? How did the constraints in connectivity among others lead to groundbreaking insights? In her session at @ThingsExpo, Carmen Feliciano, a Principal at AMDG, will answer all these questions and share how you can apply IoT best practices and frameworks from the emerging markets to your own business.
Oct. 27, 2016 03:00 AM EDT Reads: 2,691
Between the mockups and specs produced by analysts, and resulting applications built by developers, there exists a gulf where projects fail, costs spiral, and applications disappoint. Methodologies like Agile attempt to address this with intensified communication, with partial success but many limitations. In his session at @DevOpsSummit at 19th Cloud Expo, Charles Kendrick, CTO at Isomorphic Software, will present a revolutionary model enabled by new technologies. Learn how business and deve...
Oct. 27, 2016 02:45 AM EDT Reads: 1,534
Big Data has been changing the world. IoT fuels the further transformation recently. How are Big Data and IoT related? In his session at @BigDataExpo, Tony Shan, a renowned visionary and thought leader, will explore the interplay of Big Data and IoT. He will anatomize Big Data and IoT separately in terms of what, which, why, where, when, who, how and how much. He will then analyze the relationship between IoT and Big Data, specifically the drilldown of how the 4Vs of Big Data (Volume, Variety,...
Oct. 27, 2016 02:45 AM EDT Reads: 1,591
SYS-CON Events announced today that SoftNet Solutions will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. SoftNet Solutions specializes in Enterprise Solutions for Hadoop and Big Data. It offers customers the most open, robust, and value-conscious portfolio of solutions, services, and tools for the shortest route to success with Big Data. The unique differentiator is the ability to architect and ...
Oct. 27, 2016 02:15 AM EDT Reads: 1,127