VOSibilities

I am very pleased to post a recording of what I personally think was the most interesting CTO Tuesdays talk we’ve had yet. This time, Active Endpoints CTO Michael Rowley discussed BPMN 2.0 and BPEL control flows, pointing out the “trap doors” in BPMN 2.0 notation that can, for example, lead to unintended simultaneous downstream process execution and how BPEL (still using BPMN 2.0 notation) can effectively prevent hard-to-understand and -debug process applications in a BPMS.

CTO Tuesdays has been getting great feedback from our growing audience, and I’d like to offer this week’s episode as a good example of why. The discussion of BPMN 2.0 and BPEL flows is something you might not find elsewhere, delivered in an objective way and surrounded by stimulating questions and discussion with attendees. I hope you will join us every Tuesday at 17:00 GMT and participate as well. You can register at http://www.activevos.com/ctot. The replays are always available at http://www.ctotuesdays.com or via our RSS feed at http://www.ctotuesdays.com/feed

 CTO Tuesdays #6: Diamond patterns in BPEL and BPMN [51:17m]: Download (380)
 CTO Tuesdays #6: Diamond patterns in BPEL and BPMN [51:17m]: Download (259)

Bruce Silver saw my previous post on the simplicity of BPMN vs. BPEL for execution and wondered: “Are we still debating this?”

Still?

The BPMN 2.0 spec just went to beta in August and no vendor yet has an implementation of the new BPMN 2.0 execution language. So at this point the debate is just getting started. We can only compare what exists (BPMN 2.0 with BPEL execution) with the theoretical idea of a product that will someday implement the new BPMN 2.0 execution language.

At that point we will be able to get a real side-by-side comparison. Until that time, we have to guard against “shiny-new-thing syndrome,” where the newly envisioned technology gets to paint a wonderful picture looking toward the horizon, while actual working technology has to compete against that vision bearing the stains that come from living where the rubber meets the road.  Although, in this case, even the horizon envisioned by the BPMN 2.0 execution language is tainted by some pretty scary-looking smoke.

Bruce dismissed my assertion that BPMN 2.0 on top of BPEL is simpler than the new BPMN 2.0 execution language with the following:

Simpler for whom?  When you sort it all out, he’s actually saying BPEL is simpler for an engine vendor because it doesn’t have overlapping or alternative constructs like BPMN does.  No one would argue with that, but who cares?  No engine vendor is going to support every possible BPMN 2.0 element and attribute called out in the metamodel.  And I’m not saying just in the first release.  Not ever.  In that sense, BPMN 2.0 is not a self-contained execution language like BPEL is.

We disagree. Because we’ve actually built an execution engine, we know that it is actually pretty easy to implement alternative overlapping language constructs. This debate about simplicity isn’t about what a vendor can build — it’s about what the ultimate impact of that engine technology is on the user who designs and deploys processes on that engine.

My concern is for the poor person who is trying to figure out what is going wrong with a process that occasionally gets stuck. Forward progress for a process that uses the BPMN 2.0 execution language depends on a complex interplay between a huge number of constructs: event handlers, correlation mechanisms, data-flow with optional and required data, and token-based control flow that has to account for multiple tokens flowing simultaneously on a single sequence flow.

The problem with a language that is large and complex is that it is hard to have any confidence that what you’ve created will always work the way that you expect it to in production, especially when you can only test a small subset of the exponential number of possible execution scenarios.

Bruce’s admission that “BPMN is not a self-contained execution language” is noteworthy and I hope people pay close attention to it. Why do people care about standards for the languages that they use for their software? The answer is portability – primarily portability of skills but also portability of code and interoperability of tools. Basically, they are looking for an ecosystem around the language.

I love the fact that portability of skills will be enhanced by the standardization of BPMN as a notation, but for all of the constructs that are necessary to get the thing to actually execute, it seems like there are two choices: use BPEL, which is (despite assertions to the contrary) quite portable, or use some vendor’s subset/interpretation of the new BPMN 2.0 execution language. By “interpretation” I mean that even strict conformance to BPMN 2.0 admits incredible levels of freedom that are counterproductive to the creation of a language ecosystem. The most egregious example of this is the fact that the type system is pluggable. Few things are more important in a language than the type system, and yet BPMN 2.0 allows vendors to choose their own.

Bruce’s attack on the use of BPEL with BPMN rests on the assumption that: “BPEL is inherently block oriented, like a computer program, while BPMN is inherently graph oriented, like a flowchart.” Actually, BPEL supports both styles (although with some caveats). Here is a process built using ActiveVOS that is standard BPEL:

Doesn’t this look like a flow chart to you?

The one caveat that BPEL put on this style is that the loops have to be nested. This is where I agree with Bruce – without any extensions, BPEL does have an issue with “interleaved loops.” From my experience, interleaved loops are not the most common case, but if you do have a process where interleaved loops are the most natural way to represent it, what do you do? You have two choices: 1) with the use of variables, you can always rework the graph so that the loops aren’t interleaved; or, 2) you can use an extension to BPEL that removes the looping links restriction. This is an extension that is supported by both Active Endpoints and IBM and does away this nagging issue in the mapping between BPMN and BPEL. And it does this without thowing the entire language out the window and starting from scratch to make a bigger, more complex language.

We are pleased to present a recording of a webinar originally delivered on November 19, 2009 entitled Modeling Process Applications with BPMN 2.0. The webinar features Forrester Research Principal Analyst Jeffrey Hammond who delivers a talk called Balancing the Costs and Benefits of Software Modeling.

Active Endpoints CTO Michael Rowley then demonstrates using a BPMN 2.0 modeler to create executable BPEL processes.

A panel with Jeffrey and Michael follows the presentations.

Attached to this post are three files. An iPod-encoded .m4v file, a Windows Media 9-encoded file and a PDF of the slides that Jeffrey and Michael presented.

 VOSibilities podcast #39: Modeling process applications with BPMN 2.0 [80:03m]: Download (393)
 VOSibilities podcast #39: Modeling process applications with BPMN 2.0 [80:03m]: Download (4391)
 VOSibilities podcast #39: Modeling process applications with BPMN 2.0: Download (323)

BPEL is complex and BPMN is simple, right? After all, BPMN has a nice graphical notation. The BPEL standard only specifies what the language looks like in XML. That alone ought to be enough claim the prize for BPMN.

However, what if you use BPMN’s notation for a process but use BPEL for the executable representation? This removes the graphical vs. XML distinction and can “hide” the non-graphical BPEL as represented in XML. You end up with a BPMN model everyone can understand and a BPEL model your computers can execute. It’s like the two sides of a coin: there are different pictures on each side, but the coin itself is always both sides at once.

However the question of which is simpler gets more complicated when you also consider that the new BPMN 2.0 specification includes hundreds of constructs in its meta-model that have no graphical representation. Now, which is simpler, BPMN with BPEL or BPMN with the new BPMN 2.0 execution language? What may seem obvious (BPMN with BPMN 2.0 execution) isn’t the slam-dunk choice many people might expect it to be.

BPMN 2.0 has two different — but equal — compliance points for execution: BPEL Process Execution Conformance and Process Execution Conformance. This means that BPMN 2.0 standardizes the use of BPEL as the execution language for BPMN, but it also offers the option of making BPMN executable by using new constructs that have been added to the BPMN notation specifically to support execution. These new constructs depend on the execution semantics that have been defined for almost everything in BPMN.

So, which is simpler? Believe it or not, using BPMN with BPEL execution is dramatically simpler than trying to execute processes using the new BPMN 2.0 execution language. I know this sounds counter-intuitive, so I will justify it in this post and a series of follow-up posts on the same subject.

Before I get into the details of why I believe BPMN with BPEL is better, a little history might help clarify the question. There are some factors that caused the BPMN 2.0 standard to eventually become more complex than BPEL. (I know, I know, BPEL has the reputation of being far too complex…but hear me out.)

BPMN was designed to be a language for communicating from one person to another, not from a person to a machine. Languages used for human communication have a natural, and appropriate, tendancy to grow. Whenever people find that they frequently need to convey something that is awkward to express with their current vocabulary, they invent a new word. English, which is especially amenable to such growth, surpassed one million words last year. Just consider “unfriend” or “netbook,”  new words to express new ideas.

The same is true for graphical modeling languages. Look at UML (Universal Modeling Language). It started as the unification of three fairly simple graphical notations (best known by their respective primary inventors: Rumbaugh, Coad & Yourdan, and Grady Booch). Once they unified their modeling languages and people started using them in earnest, they grew larger and larger, with new diagrams and new elements on those diagrams with each successive version. Sure there was always overlap in what could be expressed by different diagrams or different elements, but in each case, there were situations where one was more natural to the reader than the other. The fact that different constructs have imprecise overlapping meanings is of little concern in a language meant for people, since people are comfortable with choosing among a variety of ways of expressing the same thing, each with their own nuances and connotations.

But while notation creep is a useful way of expanding spoken languages or graphical notations, it is not such a good thing for a language that must be directly executable on a computer.

That’s because it is always a problem to take such a large language and give it formal executable semantics. The problem usually isn’t with a lack of rigor in the definition of any one construct. The problem is with the exponential number of combinations of those constructs.

Good programming languages typically add new fundamental primitives very cautiously. Consider how much hard preparatory work was done in the Java community before Java introduced generics into the language, or the hand wringing that is gripping that community as they grapple with the addition of closures to the language. The way it typically works is that some eminently-respectable, highly-credentialed expert (like Neal Gafter, in the case of closures) will make a seemingly very well-thought-out proposal that describes how the new construct will simplify the lives of so many programmers. Then another equally eminent expert (like Josh Bloch, in this case) will find unintended consequences of the new construct when it is used in combination with other things in the language.

That was just for one language feature. The BPMN 2.0 execution language has dozens of features that have never really been used together in an execution language. For example, the BPMN 2.0 execution not only has a variety of ways of handing the control flow for multiple incoming sequence flows, activities also can’t execute until all of the required inputs from one of the activities input datasets has become available. In other words, it has a fairly complex data flow model intertwined with its control flow model.

Another example is message correlation. BPEL has, in the past, been criticized for the complexity of its approach to correlation, but BPMN has two different correlation mechanisms. Key-based correlation is basically equivalent to BPEL’s correlation mechanism, although the standard has invented all new terminology for the various components. It then defines a new concept of context-based correlation. Rather than trying to convince you that it is complex, I’ll just include the complete explanation of it from the BPMN 2.0 specification (yes, in a 500-page specification, there are no examples or additional explanations for these concepts):

In context-based correlation, the Process context (i.e., its Data Objects and Properties) may dynamically influence the matching criterion. That is, a CorrelationKey may be complemented by a Process-specific CorrelationSubscription. A CorrelationSubscription aggregates as many CorrelationProperty-Bindings as there are CorrelationProperties in the CorrelationKey. A CorrelationPropertyBinding relates to a specific CorrelationProperty and also links to a Formal-Expression which denotes a dynamic extraction rule atop the Process context. At runtime, the Correlation-Key instance for a particular Conversation is populated (and dynamically updated) from the Process context using these FormalExpressions. In that sense, changes in the Process context may alter the correlation condition.

Confused yet? Are you wondering not just why BPMN 2.0 needed to define and redefine an important concept like message correlation, but also wondering how, precisely, to implement BPMN correlation?

These are just a couple of the ways that BPMN’s new execution language is more complex that using BPMN with BPEL. BPEL is now a known commodity. It’s widely implemented. Many production applications are running BPEL today. There are many people with experience with it and the concepts in the language are well understood. With BPMN 2.0, it now has a standardized notation, so there is no need to work with a new language that is a big bag of language constructs whose interactions have never been exercised together.

In episode #5 of our continuing webinar series on technical topics of interest to developers, architects and business analysts working with SOA-based business process management systems (BPMS), Dr. Michael Rowley, CTO, Active Endpoints compares and contrasts two different styles of message correlation. In episode #4, Michael outlined message correlation as defined by the BPEL standard. In this episode, Michael illustrates a different style of correlation, which relies on the execution engine to correlate incoming messages to specific processes. Michael also describes when and how each style (BPEL-managed vs. engine-managed) can be used and notes some pros and cons for each style.

There are two attached versions of the webinar replay (an iPod-formatted .m4v and a DivX-encoded .avi). As always, you can register for the next episode of CTO Tuesdays at http://www.activevos.com/ctot. We look forward to your comments, suggestions and feedback.

 CTO Tuesdays #5: Engine-managed correlation [30:10m]: Download (380)
 CTO Tuesdays #5: Engine-managed correlation [30:10m]: Download (344)

I have good news and bad news. The good news is that we (finally) have replays of episode #4 of CTO Tuesdays, our regular weekly webinar on BPM topics of interest to process designers and developers. The subject of this webinar is message correlation, an interesting topic that details how systems match up running processes and the messages for those running processes.

The bad news is that due to a technical issue, the audio for the host, our own Sonal Rajan, wasn’t recorded. This is shame because at the end of each topic, we always have an open Q&A session on the current topic to amplify the technical discussion. Unfortunately, these replays won’t have that Q&A because there’s no audio for the moderator. However, the actual presentation about message correlation was recorded just fine.

In the two attached versions of the webinar replay (an iPod-formatted .m4v and a DivX-encoded .avi), I have edited most of the silent introduction and the Q&A.

As always, you can register for the next episode of CTO Tuesdays at http://www.activevos.com/ctot.

 CTO Tuesdays #4: Message correlation [35:53m]: Download (429)
 CTO Tuesdays #4: Message correlation [35:53m]: Download (456)

BPMN 2.0 and WS-BPEL 2.0 are the two most important standards for BPM today. But why are there two? Can’t you just care about BPEL or just care about BPMN? In fact, both standards matter and the two should be used together. To back that up, I have to convince you both that BPEL needs BPMN and that BPMN needs BPEL. In today’s post, I’ll concentrate on the first: why BPEL needs BPMN.

First, lets assume that you are convinced of the value of BPEL. You see that it is a great high-level language for creating business processes and orchestrating services. Its service-centric approach is simpler and better for long-term manageability and reuse than other approaches to business process management. It is an accepted OASIS standard with multiple vendor implementations, so investments in BPEL processes are not tied to a single vendor and you can find people who already know the language without having to train them from scratch.

But if you are convinced you want BPEL, why should you care about BPMN? There are two main reasons:

1) To get the value of a standard notation;

2) To improve collaboration with a wide variety of stakeholders in the process, since BPMN is a significant simplification over existing notations used for BPEL.

When WS-BPEL 2.0 was standardized, the OASIS Technical Committee chose not to standardize a graphical notation for it. This was unfortunate, since no one creates a business process by writing BPEL in XML, which is the only standardized representation. Every vendor, and every BPEL developer, creates their processes using a graphical representation, but that representation is different for every tool.

And the notations used by these tools haven’t really been very good. They typically provide a one-to-one correspondence between control flow constructs in BPEL and things on the canvas. However, if you use the BPMN notation, it shows a notation that can mostly be understood without any knowledge of BPEL or even BPMN for that matter (as long as the labels are chosen carefully).

Let me make both of these points with the help of a trivial process example. Take a look at the BPMN representation of a process that I’ll call the “Question” process.

(Click on each image to see a larger version)

It is trivial to follow what is going on, especially if you know the standard notation. You can’t tell by looking at this diagram, but I’ve used two different BPEL mechanisms for getting to the next activity. I use a BPEL link to get from “Receive Q” to the first diamond (the beginning of the BPEL if statement). I use a BPEL sequence to get from the second diamond (the end of the if) to the “Record Answer” activity.

The user who is looking at the graphical representation of the process doesn’t need to know about the distinction between these two mechanisms, so the diagram doesn’t show a difference. The developer may want to know about the difference, so ActiveVOS highlights them differently on mouse-over and shows them differently in the “process outline view”, but that isn’t really important for today’s discussion.

What is important is how different the process is represented in different tools due to the fact that no notation had been standardized. I’ll show what this process looks like in three different BPEL process designers.

Here is how ActiveVOS would represent this process in previous versions of the product (or using the optional “classic” style in 7.0):

Here is how the Eclipse BPEL Designer represents it:

And, here is how the designer for Oracle’s BPEL Process Manager represents it:

In all three of these representations, each of the paths through the if statement are represented by a bounding box. The problem with this representation is that nested if statements can result in so many nested bounding boxes that it is hard to follow what is going on. BPMN simply has arrows through each path and the paths merge back into a single control flow at a gateway diamond.

Also notice the differences in the handling of links vs. sequences. Both ActiveVOS classic and Eclipse represent sequences with their own bounding boxes, then any arrow that is a direct child of a sequence box is known to belong to the sequence, rather than being a real link. Eclipse also draws the links in different color. The extra sequence icon and corresponding bounding box just interferes with the ability for non-technical users to follow what is going on in the process.

Oracle’s designer is odd in this respect. Sequences are not shown in a bounding box, so they don’t clutter up the control flow (a good thing in my opinion), but links aren’t shown at all! There is a link from the “Receive_Q” activity to the if statement, but there isn’t any representation of it on the diagram. It shows the “Receive_Q” and the if as if they happen in parallel. You have to look into the properties of “Receive_Q” to discover that it has an outgoing link, and further rummaging to find out where it goes.

The BPMN representation is, by far, the easiest version of this small process to understand. The process illustrates just three constructs whose representation is simpler with BPMN than with other approaches: ifs, sequences and links. The other BPEL constructs are generally as easy or easier for non-technical users to understand than previous approaches.

But, as valuable as the improvement in readability may be, the greater value that BPMN brings to be BPEL is probably consistency. Having different tools represent similar constructs in such different ways is detrimental to one of the key values in having a standard: skills portability. With a common notation, people will be able to carry their knowledge of how to understand and work with standards-based business processes between vendor tools. It will also create a greater incentive for people to learn these technologies and for schools to teach them. After all, people aren’t usually to thrilled about investing a lot of energy into learning proprietary technologies, and no school really wants to be teaching proprietary technologies.

This week on CTO Tuesdays Active Endpoints CTO Michael Rowley presented how events are represented in BPMN 2.0 and BPEL.

I think you will find Michael’s explanation of BPMN 2.0 event notation especially valuable.

I have attached two versions of the recorded webinar to this post. The first is an iPod-formatted .m4v. Also attached to this post is a Windows Media format .wmv file.

We have also made signing up for CTO Tuesdays and accessing the replays much easier. You can always sign up for the upcoming session of CTO Tuesdays at http://www.activevos.com/ctot. Replays are always available at http://www.ctotuesdays.com. And, an RSS feed of the replays is available at http://www.ctotuesdays.com/feed.

 CTO Tuesdays #3: BPMN and BPEL events [43:57m]: Download (448)
 CTO Tuesdays #3: BPMN and BPEL events [43:57m]: Download (4477)

This week’s topic on CTO Tuesdays was an introduction to the new WS-HumanTask standard for workflow. In this informative session, Michael Rowley describes the importance of the new standard for workflow, how it separates tasks from processing and how WS-HumanTask enables human activities to be seen as services in a process application.

Attached to this post are three files. A PDF of the slides Dr. Rowley presented, an iPod-formatted .m4v file (which requires QuickTime or iTunes to be installed) and a more-or-less standard .avi file. The .avi is the larger of the two video files.

Due to a technical error (I didn’t press “show” on GoToMeeting), the first few minutes of the video show Michael’s slides, not the ones I am discussing. Since this is just an introduction, you won’t miss anything. I’ve put those “missing” slides into the .pdf file, so you can follow along if you want to.

We had a very lively panel discussion at the end of the presentation; I hope you’ll have the time to listen to the discussion that follows the presentation.

As always, we are very interested in your feedback, comments and topic suggestions.

One more note: you can always register for the upcoming CTO Tuesdays session by visiting http://www.activevos.com/ctot. We hope you join us for next week’s webinar.

 CTO Tuesdays #2: Introduction to WS-HumanTask [49:03m]: Download (8502)
 CTO Tuesdays #2: Introduction to WS-HumanTask [48:56m]: Download (1084)
 CTO Tuesdays #2: Introduction to WS-HumanTask: Download (306)

We are very pleased to post the recording of the first episode of our new weekly webinar on BPM technology called CTO Tuesdays.

Every Tuesday, Active Endpoints’ CTO Michael Rowley, will present a topic of interest to BPM users. Our inaugural topic was an explanation of the meaning and uses of the BPMN 2.0 diamond symbol. If you are interested in learning BPMN 2.0 — or if you just want to brush up on some of the more advanced considerations in using this basic BPMN symbol — you will find this recording very instructive. Concepts are demonstrated in ActiveVOS 7’s new BPMN 2.0 modeler.

Attached to this post are two versions of the webinar: an iPod-formatted .m4v file our podcast subscribers will automatically receive and an H.264-encoded .avi file (which is much larger at about 113MB).

We welcome your input and suggestions for CTO Tuesdays. Contact us via email at editor at activevos dot com. Today, the best way to be notified of upcoming CTO Tuesdays is to be on our mailing list. And, the best way to get onto our mailing list is to download a trial of ActiveVOS. You can also register for upcoming CTO Tuesdays by clicking on the link in the right hand column of any interior page on www.activevos.com.

We are working hard on making registering for CTO Tuesdays easier. But because of the demand for education on topics like BPMN 2.0, we started the webinar series without waiting to dot all the “i’s” and cross all our “t’s.”

Update: You can now register for CTO Tuesdays by clicking the link in the right-hand column of any page on www.activevos.com except the home page. So, just navigate into the site a little and you’ll get a little reward: easy access to registration for CTO Tuesdays.

Updated update: You can now always register for the upcoming CTO Tuesdays at http://www.activevos.com/ctot.

We hope you enjoy this recording and that you will join us as your schedule permits for the live CTO Tuesdays every Tuesday at noon ET, 9am PT, 16:00 GMT (17:00 GMT after the end of US daylight savings time in November, 2009).

 

 CTOT #1: The BPMN diamond [39:32m]: Play Now | Play in Popup | Download (4604)
 CTOT #1: The BPMN diamond [39:30m]: Download (7405)

Dennis Byron uses a clever metaphor (“Is it floor wax or dessert topping?”) as a way to describe what’s new in ActiveVOS 7.0 in a post on itbusinessedge.com.

Last week, CTO Michael Rowley and I showed ActiveVOS 7 to Rob Barry of TechTarget’s SOA Talk blog.  I know it’s a party foul to quote yourself in a blog post, but we are grateful that Rob chose to highlight one of the main accomplishments we believe we have achieved for BPM in ActiveVOS 7:

“BPM suites that focus on business users, they don’t get technical enough,” said Alex Neihaus, VP of marketing at Active Endpoints. “They become islands of computing and sit off by themselves. And with BPMS for architects and developers, the level of cost and complexity is beyond the level of what most people are willing to undertake.”

This “third way” between the cost and complexity of stacks from Oracle and IBM and the unfulfilled promises of Lombardi and Pegasystems to integrate easily across the enterprise are why we believe we have become so popular among development teams. Looking past old buying habits and the new politics of “end user” BPM, our customers are seeking great technology at an affordable price that can be used to create integrated processes as that are themselves services.

You can read Rob’s entire blog post here.

As we promised in part 1 of of our discussion on the new features in the ActiveVOS 7 BPMS, we are delighted to post part 2 of a conversation among me (Alex Neihaus), Luc Clément and Michael Rowley. In this second podcast, Michael and Luc cover topics that are of interest to enterprise architects, developers and operations staff. Topics include continuous development (including support for the open-source Hudson project) and new features in the BPMN designer that improve productivity and operational enhancements.

We hope you enjoy this podcast.

 

 VOSibilities podcast #37: ActiveVOS 7.0, part 2 [28:32m]: Play Now | Play in Popup | Download (1595)

We’re very excited to be able to post a sneak preview of the brand-new BPMN 2.0 designer that’s coming in ActiveVOS 7.0.

We’ve also posted a screenshot tour of our new ActiveVOS Central application.

We hope to have additional screenshot galleries up soon.

ActiveVOS 7.0 is a major new release of the business process management system (BPMS) that development teams love. The document attached to this post gives an overview of new features in the release. The document discusses the new BPMN 2.0-compliant modeler with BPEL execution and no round-trip problems, a new AJAX capable services-based forms designer and ActiveVOS Central. ActiveVOS Central is a complete, out-of-the-box solution for managing work, accessing reports and graphs of system activity and creating processes. In addition, the document describes additional new features of the BPMS that improve productivity and enhance collaboration between an extended development team and end users.

This version is a draft of the What’s New in ActiveVOS 7.0 document. Please check back frequently for updated versions.

 What's New in ActiveVOS 7.0: Download (1003)