Comments on: Automating the BPMN-BPEL “Interleaving” Solution http://www.brsilver.com/wordpress/2008/04/05/automating-the-bpmn-bpel-interleaving-solution/ Bruce Silver's blog on business process management Thu, 03 Jul 2008 22:35:50 +0000 http://wordpress.org/?v=2.5.1 By: kswenson http://www.brsilver.com/wordpress/2008/04/05/automating-the-bpmn-bpel-interleaving-solution/#comment-4818 kswenson Wed, 09 Apr 2008 15:30:05 +0000 http://www.brsilver.com/wordpress/2008/04/05/automating-the-bpmn-bpel-interleaving-solution/#comment-4818 About comment #4, Bruce, you are right, you are still duplicating a gateway, which is a lesser sin than duplicating an activity. IMHO. About BPEL graphs: the example I saw on graph style had a bunch of parallel activities that used links to coordinate the start and stop of each activity -- preventing one activity from starting before another activity ended. Graph-style would be sufficient for representing the drawings, BUT when I last investigated this there were a lot of unanswered questions about how you terminate the process. The precise meaning of certain kinds of transitions (like loops that have links that cross threads) was not clear. ALSO, with the graph-style how can one get any of the advantages of being block structured: exception throwing? nested scopes? transaction boundaries? Seems like all of those would be lost. About comment #4, Bruce, you are right, you are still duplicating a gateway, which is a lesser sin than duplicating an activity. IMHO.

About BPEL graphs: the example I saw on graph style had a bunch of parallel activities that used links to coordinate the start and stop of each activity — preventing one activity from starting before another activity ended. Graph-style would be sufficient for representing the drawings, BUT when I last investigated this there were a lot of unanswered questions about how you terminate the process. The precise meaning of certain kinds of transitions (like loops that have links that cross threads) was not clear. ALSO, with the graph-style how can one get any of the advantages of being block structured: exception throwing? nested scopes? transaction boundaries? Seems like all of those would be lost.

]]> By: sebastian http://www.brsilver.com/wordpress/2008/04/05/automating-the-bpmn-bpel-interleaving-solution/#comment-4817 sebastian Wed, 09 Apr 2008 12:37:22 +0000 http://www.brsilver.com/wordpress/2008/04/05/automating-the-bpmn-bpel-interleaving-solution/#comment-4817 @Bruce: I'm not aware of a single tool transforming to BPEL graph-style. I only know of 2 reasons for that, but I think both reasons are not really convincing: 1) BPEL graphs are hard to understand and maintain by a human user. --> But why is it easy for people to do graph modelling with BPMN but not with BPEL? 2) BPEL graphs are not portable. --> I have no proof for that. It might have been true some years ago, but I think now most engines are compliant to the full spec. Any other reasons? @Bruce: I’m not aware of a single tool transforming to BPEL graph-style. I only know of 2 reasons for that, but I think both reasons are not really convincing:

1) BPEL graphs are hard to understand and maintain by a human user. –> But why is it easy for people to do graph modelling with BPMN but not with BPEL?

2) BPEL graphs are not portable. –> I have no proof for that. It might have been true some years ago, but I think now most engines are compliant to the full spec.

Any other reasons?

]]> By: bruce http://www.brsilver.com/wordpress/2008/04/05/automating-the-bpmn-bpel-interleaving-solution/#comment-4816 bruce Tue, 08 Apr 2008 23:24:47 +0000 http://www.brsilver.com/wordpress/2008/04/05/automating-the-bpmn-bpel-interleaving-solution/#comment-4816 Point well taken, Sebastian. Again, my point is more about tools and roundtripping than about fundamental capabilities of BPEL. I believe WebSphere Modeler generates link-oriented BPEL from its graph-oriented (not BPMN) models, but I don't know of any other tools that use the links. Do you? To restate the need, it's that the tool automatically create the BPEL from BPMN, and - ideally - recover the BPMN from BPEL in the reverse direction. I gave Intalio points for doing some of it. Do you know of tools that do this using links? --Bruce Point well taken, Sebastian. Again, my point is more about tools and roundtripping than about fundamental capabilities of BPEL. I believe WebSphere Modeler generates link-oriented BPEL from its graph-oriented (not BPMN) models, but I don’t know of any other tools that use the links. Do you? To restate the need, it’s that the tool automatically create the BPEL from BPMN, and - ideally - recover the BPMN from BPEL in the reverse direction. I gave Intalio points for doing some of it. Do you know of tools that do this using links?
–Bruce

]]> By: sebastian http://www.brsilver.com/wordpress/2008/04/05/automating-the-bpmn-bpel-interleaving-solution/#comment-4813 sebastian Tue, 08 Apr 2008 19:24:03 +0000 http://www.brsilver.com/wordpress/2008/04/05/automating-the-bpmn-bpel-interleaving-solution/#comment-4813 By the way folks, why do we have to map BPMN to block-oriented BPEL? BPEL also has a graph-oriented character using links. So how do you motivate that a mapping to block-oriented BPEL is needed? By the way folks, why do we have to map BPMN to block-oriented BPEL? BPEL also has a graph-oriented character using links. So how do you motivate that a mapping to block-oriented BPEL is needed?

]]> By: bruce http://www.brsilver.com/wordpress/2008/04/05/automating-the-bpmn-bpel-interleaving-solution/#comment-4808 bruce Mon, 07 Apr 2008 15:20:26 +0000 http://www.brsilver.com/wordpress/2008/04/05/automating-the-bpmn-bpel-interleaving-solution/#comment-4808 Keith, I don't doubt what you say, but you are still effectively duplicating a diagram node, so let me restate my complaint. Mapping BPMN to BPEL automatically requires smart algorithms that can analyze the topology of a diagram and insert additional gateways (per your example) or activities (Intalio), or else report errors that the modeler has to fix himself (ITP). Keith,
I don’t doubt what you say, but you are still effectively duplicating a diagram node, so let me restate my complaint. Mapping BPMN to BPEL automatically requires smart algorithms that can analyze the topology of a diagram and insert additional gateways (per your example) or activities (Intalio), or else report errors that the modeler has to fix himself (ITP).

]]> By: kswenson http://www.brsilver.com/wordpress/2008/04/05/automating-the-bpmn-bpel-interleaving-solution/#comment-4806 kswenson Mon, 07 Apr 2008 06:31:03 +0000 http://www.brsilver.com/wordpress/2008/04/05/automating-the-bpmn-bpel-interleaving-solution/#comment-4806 Bruce, This diagram should not have any threading problems, any block problems, if you consider the first XOR splits be two XOR splits: the first one brakes the upper branchs from the lower one, and then the second XOR split splits the upper two, which come back together. This would be realized in the block structure as an outer if statement, and then inside the first block having another if statement. If you convert from the BPMN to the block structured language well enough, you will not need to duplicate any blocks. You get the interleaving error because the conversion does not recognize that the upper two paths are special because they come back together sooner than the lower one......I think. What you don't have in this diagram is the "figure 8" shape. This is a shape that was drawn long ago by W Van der Aalst when discussing the limitations of BPEL. The figure-8 shape is a long rectangle, where the top is one branch, and the bottom the other, and you have an arrow that crosses from the upper to the lower somewhere in the middle (or lower to upper as the diagram in your last post did). The figure-8 can not be handled in a block structured language, and must be resolved by duplicating nodes/paths. -Keith Bruce,

This diagram should not have any threading problems, any block problems, if you consider the first XOR splits be two XOR splits: the first one brakes the upper branchs from the lower one, and then the second XOR split splits the upper two, which come back together.

This would be realized in the block structure as an outer if statement, and then inside the first block having another if statement. If you convert from the BPMN to the block structured language well enough, you will not need to duplicate any blocks. You get the interleaving error because the conversion does not recognize that the upper two paths are special because they come back together sooner than the lower one……I think.

What you don’t have in this diagram is the “figure 8″ shape. This is a shape that was drawn long ago by W Van der Aalst when discussing the limitations of BPEL. The figure-8 shape is a long rectangle, where the top is one branch, and the bottom the other, and you have an arrow that crosses from the upper to the lower somewhere in the middle (or lower to upper as the diagram in your last post did). The figure-8 can not be handled in a block structured language, and must be resolved by duplicating nodes/paths.

-Keith

]]> By: bruce http://www.brsilver.com/wordpress/2008/04/05/automating-the-bpmn-bpel-interleaving-solution/#comment-4803 bruce Sun, 06 Apr 2008 04:34:43 +0000 http://www.brsilver.com/wordpress/2008/04/05/automating-the-bpmn-bpel-interleaving-solution/#comment-4803 OK. I guess I really should be paying more attention to that tool. Just like Ismael keeps telling me. --Bruce OK. I guess I really should be paying more attention to that tool. Just like Ismael keeps telling me.
–Bruce

]]> By: frenchdk http://www.brsilver.com/wordpress/2008/04/05/automating-the-bpmn-bpel-interleaving-solution/#comment-4802 frenchdk Sun, 06 Apr 2008 01:42:18 +0000 http://www.brsilver.com/wordpress/2008/04/05/automating-the-bpmn-bpel-interleaving-solution/#comment-4802 No, I can confirm that Intalio will allow you to draw your first example in BPMN without merge gateways (ie the same as you drew it) and will generate and run bpel as intended. regards David No, I can confirm that Intalio will allow you to draw your first example in BPMN without merge gateways (ie the same as you drew it) and will generate and run bpel as intended. regards David

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