|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.
Have you ever noticed how some IT people seem to lead successful, rewarding, and satisfying lives and careers, while others struggle? IT author and speaker Don Crawley uncovered the five principles that successful IT people use to build satisfying lives and careers and he shares them in this fast-paced, thought-provoking webinar. You'll learn the importance of striking a balance with technical skills and people skills, challenge your pre-existing ideas about IT customer service, and gain new in...
Mar. 26, 2017 11:00 AM EDT Reads: 2,494
SYS-CON Events announced today that T-Mobile will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. As America's Un-carrier, T-Mobile US, Inc., is redefining the way consumers and businesses buy wireless services through leading product and service innovation. The Company's advanced nationwide 4G LTE network delivers outstanding wireless experiences to 67.4 million customers who are unwilling to compromise on ...
Mar. 26, 2017 11:00 AM EDT Reads: 2,156
In his session at @ThingsExpo, Eric Lachapelle, CEO of the Professional Evaluation and Certification Board (PECB), will provide an overview of various initiatives to certifiy the security of connected devices and future trends in ensuring public trust of IoT. Eric Lachapelle is the Chief Executive Officer of the Professional Evaluation and Certification Board (PECB), an international certification body. His role is to help companies and individuals to achieve professional, accredited and worldw...
Mar. 26, 2017 10:45 AM EDT Reads: 597
SYS-CON Events announced today that Juniper Networks (NYSE: JNPR), an industry leader in automated, scalable and secure networks, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Juniper Networks challenges the status quo with products, solutions and services that transform the economics of networking. The company co-innovates with customers and partners to deliver automated, scalable and secure network...
Mar. 26, 2017 10:30 AM EDT Reads: 1,282
SYS-CON Events announced today that Infranics will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Since 2000, Infranics has developed SysMaster Suite, which is required for the stable and efficient management of ICT infrastructure. The ICT management solution developed and provided by Infranics continues to add intelligence to the ICT infrastructure through the IMC (Infra Management Cycle) based on mathemat...
Mar. 26, 2017 10:15 AM EDT Reads: 2,993
SYS-CON Events announced today that SD Times | BZ Media has been named “Media Sponsor” of SYS-CON's 20th International Cloud Expo, which will take place on June 6–8, 2017, at the Javits Center in New York City, NY. BZ Media LLC is a high-tech media company that produces technical conferences and expositions, and publishes a magazine, newsletters and websites in the software development, SharePoint, mobile development and commercial UAV markets.
Mar. 26, 2017 09:30 AM EDT Reads: 4,279
SYS-CON Events announced today that Cloudistics, an on-premises cloud computing company, has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Cloudistics delivers a complete public cloud experience with composable on-premises infrastructures to medium and large enterprises. Its software-defined technology natively converges network, storage, compute, virtualization, and management into a ...
Mar. 26, 2017 09:15 AM EDT Reads: 1,943
Now that the world has connected “things,” we need to build these devices as truly intelligent in order to create instantaneous and precise results. This means you have to do as much of the processing at the point of entry as you can: at the edge. The killer use cases for IoT are becoming manifest through AI engines on edge devices. An autonomous car has this dual edge/cloud analytics model, producing precise, real-time results. In his session at @ThingsExpo, John Crupi, Vice President and Eng...
Mar. 26, 2017 09:00 AM EDT Reads: 3,867
SYS-CON Events announced today that Loom Systems will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Founded in 2015, Loom Systems delivers an advanced AI solution to predict and prevent problems in the digital business. Loom stands alone in the industry as an AI analysis platform requiring no prior math knowledge from operators, leveraging the existing staff to succeed in the digital era. With offices in S...
Mar. 26, 2017 09:00 AM EDT Reads: 1,236
Historically, some banking activities such as trading have been relying heavily on analytics and cutting edge algorithmic tools. The coming of age of powerful data analytics solutions combined with the development of intelligent algorithms have created new opportunities for financial institutions. In his session at 20th Cloud Expo, Sebastien Meunier, Head of Digital for North America at Chappuis Halder & Co., will discuss how these tools can be leveraged to develop a lasting competitive advanta...
Mar. 26, 2017 08:15 AM EDT Reads: 2,683
SYS-CON Events announced today that HTBase will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. HTBase (Gartner 2016 Cool Vendor) delivers a Composable IT infrastructure solution architected for agility and increased efficiency. It turns compute, storage, and fabric into fluid pools of resources that are easily composed and re-composed to meet each application’s needs. With HTBase, companies can quickly prov...
Mar. 26, 2017 08:15 AM EDT Reads: 2,876
There are 66 million network cameras capturing terabytes of data. How did factories in Japan improve physical security at the facilities and improve employee productivity? Edge Computing reduces possible kilobytes of data collected per second to only a few kilobytes of data transmitted to the public cloud every day. Data is aggregated and analyzed close to sensors so only intelligent results need to be transmitted to the cloud. Non-essential data is recycled to optimize storage.
Mar. 26, 2017 08:15 AM EDT Reads: 2,980
"I think that everyone recognizes that for IoT to really realize its full potential and value that it is about creating ecosystems and marketplaces and that no single vendor is able to support what is required," explained Esmeralda Swartz, VP, Marketing Enterprise and Cloud at Ericsson, in this SYS-CON.tv interview at @ThingsExpo, held June 7-9, 2016, at the Javits Center in New York City, NY.
Mar. 26, 2017 08:00 AM EDT Reads: 4,150
SYS-CON Events announced today that SoftLayer, an IBM Company, has been named “Gold Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2016, at the Javits Center in New York, New York. SoftLayer, an IBM Company, provides cloud infrastructure as a service from a growing number of data centers and network points of presence around the world. SoftLayer’s customers range from Web startups to global enterprises.
Mar. 26, 2017 07:15 AM EDT Reads: 1,660
While DevOps most critically and famously fosters collaboration, communication, and integration through cultural change, culture is more of an output than an input. In order to actively drive cultural evolution, organizations must make substantial organizational and process changes, and adopt new technologies, to encourage a DevOps culture. Moderated by Andi Mann, panelists discussed how to balance these three pillars of DevOps, where to focus attention (and resources), where organizations might...
Mar. 26, 2017 05:15 AM EDT Reads: 6,162