Welcome!

Related Topics: Microservices Expo

Microservices Expo: Article

A Close Look at BPEL 2.0

Drilling down to the next level of detail

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!

Dynamic Parallelism
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.).


More Stories By Manoj Das

Manoj Das is senior manager in the product management group for Oracle Fusion Middleware. His focus is on BPEL and Business Rules. Manoj joins Oracle from the Siebel acquisition where he was responsible for driving the next generation process-centric application platform.

More Stories By Alex Yiu

Alex Yiu represents Oracle as an editor in the WS-BPEL 2.0 specification, WS-BPEL 2.0 primer, and SCA (Service Component Architecture) BPEL specification. He was also a part of the joint-group task-force that designed Oracle’s cross-tier binary XML format (patent pending). Prior to that, Alex represented Oracle in the JavaServer Pages JCP Expert Groups and was a speaker for a JavaOne technical session on the topic of XML Data Integration.

More Stories By Khanderao Kand

Khanderao Kand is a Lead Architect for Oracle Fusion Middleware at Oracle Corp. He is involved in the development of Oracle’s SOA Suite covering various Integration and BPM technologies including BPEL and ESB. He also provides Architectural consultancy for Oracle’s next generation Fusion Applications to architect their solutions around SOA and BPM. He has been involved in the development of various industry standards like BPEL 2.0, SCA-Assembly, SCA-BPEL etc. In his two decades of Software Development experience, he played various roles like an Enterprise Architect of Peopletools, an architect in CRM and others. Being a code slinger, he plays around with various emerging tools and technologies. Occasionally he writes in technical magazines like Java Developers Journal, Web Services Journal, SOA World etc. He also speaks at various conferences like Oracle Open World, JAX Conference, and Software Development Best Practices.

Comments (1) View Comments

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


Most Recent Comments
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.

Well done,

Yours, Mike.

Latest Stories
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 18th Cloud Expo, Charles Kendrick, CTO & Chief Architect at Isomorphic Software, will present a revolutionary model enabled by new technologies. Learn how business and devel...
You think you know what’s in your data. But do you? Most organizations are now aware of the business intelligence represented by their data. Data science stands to take this to a level you never thought of – literally. The techniques of data science, when used with the capabilities of Big Data technologies, can make connections you had not yet imagined, helping you discover new insights and ask new questions of your data. In his session at @ThingsExpo, Sarbjit Sarkaria, data science team lead ...
The IoT has the potential to create a renaissance of manufacturing in the US and elsewhere. In his session at 18th Cloud Expo, Florent Solt, CTO and chief architect of Netvibes, will discuss how the expected exponential increase in the amount of data that will be processed, transported, stored, and accessed means there will be a huge demand for smart technologies to deliver it. Florent Solt is the CTO and chief architect of Netvibes. Prior to joining Netvibes in 2007, he co-founded Rift Technol...
If there is anything we have learned by now, is that every business paves their own unique path for releasing software- every pipeline, implementation and practices are a bit different, and DevOps comes in all shapes and sizes. Software delivery practices are often comprised of set of several complementing (or even competing) methodologies – such as leveraging Agile, DevOps and even a mix of ITIL, to create the combination that’s most suitable for your organization and that maximize your busines...
Struggling to keep up with increasing application demand? Learn how Platform as a Service (PaaS) can streamline application development processes and make resource management easy.
New Relic, Inc. has announced a set of new features across the New Relic Software Analytics Cloud that offer IT operations teams increased visibility, and the ability to diagnose and resolve performance problems quickly. The new features further IT operations teams’ ability to leverage data and analytics, as well as drive collaboration and a common, shared understanding between teams. Software teams are under pressure to resolve performance issues quickly and improve availability, as the comple...
The proper isolation of resources is essential for multi-tenant environments. The traditional approach to isolate resources is, however, rather heavyweight. In his session at 18th Cloud Expo, Igor Drobiazko, co-founder of elastic.io, will draw upon their own experience with operating a Docker container-based infrastructure on a large scale and present a lightweight solution for resource isolation using microservices. He will also discuss the implementation of microservices in data and applicat...
Join IBM June 8 at 18th Cloud Expo at the Javits Center in New York City, NY, and learn how to innovate like a startup and scale for the enterprise. You need to deliver quality applications faster and cheaper, attract and retain customers with an engaging experience across devices, and seamlessly integrate your enterprise systems. And you can't take 12 months to do it.
See storage differently! Storage performance problems have only gotten worse and harder to solve as applications have become largely virtualized and moved to a cloud-based infrastructure. Storage performance in a virtualized environment is not just about IOPS, it is about how well that potential performance is guaranteed to individual VMs for these apps as the number of VMs keep going up real time. In his session at 18th Cloud Expo, Dhiraj Sehgal, in product and marketing at Tintri, will discu...
Machine Learning helps make complex systems more efficient. By applying advanced Machine Learning techniques such as Cognitive Fingerprinting, wind project operators can utilize these tools to learn from collected data, detect regular patterns, and optimize their own operations. In his session at 18th Cloud Expo, Stuart Gillen, Director of Business Development at SparkCognition, will discuss how research has demonstrated the value of Machine Learning in delivering next generation analytics to im...
This is not a small hotel event. It is also not a big vendor party where politicians and entertainers are more important than real content. This is Cloud Expo, the world's longest-running conference and exhibition focused on Cloud Computing and all that it entails. If you want serious presentations and valuable insight about Cloud Computing for three straight days, then register now for Cloud Expo.
As you respond to increasing requests for new analytics, you need fast and flexible technology in your arsenal so that you can deploy the right workload to the right platform for the need at hand. Do you need self-service and fast time to value? Do you have data and application control and privacy needs, along with strict SLAs to meet? IBM dashDB™ is data warehouse technology powered by in-memory computing and in-database analytics that are designed for fast results, scalability and more.
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.
So, you bought into the current machine learning craze and went on to collect millions/billions of records from this promising new data source. Now, what do you do with them? Too often, the abundance of data quickly turns into an abundance of problems. How do you extract that "magic essence" from your data without falling into the common pitfalls? In her session at @ThingsExpo, Natalia Ponomareva, Software Engineer at Google, will provide tips on how to be successful in large scale machine lear...
Up until last year, enterprises that were looking into cloud services usually undertook a long-term pilot with one of the large cloud providers, running test and dev workloads in the cloud. With cloud’s transition to mainstream adoption in 2015, and with enterprises migrating more and more workloads into the cloud and in between public and private environments, the single-provider approach must be revisited. In his session at 18th Cloud Expo, Yoav Mor, multi-cloud solution evangelist at Cloudy...