Message flow between lanes

[Janelle Carter]

Hi,

Are message flows allowed between lanes?

The OCEB Certification guide states "Messages can only be used for communication between participants from different pools. They are not permitted for the communication between lanes within a pool."

However this presentation by OMG shows lane to lane message flow examples (page 57): http://www.omg.org/news/meetings/workshops/SOA-HC/presentations-2011/14_MT-2_Brookshier.pdf

So which is correct? 

In practice, I see analysts using swimlanes to represent different roles or departments within an organisation. It makes sense to me that you can have message flow between different roles or departments. If however, lanes are only there for organising and categorising a set of activities, then maybe it shouldn't be allowed.

I'm a beginner with BPMN so thanks for your patience!

Cheers,

Janelle

[David Sanders]

Yeah that presentation is incorrect :)  I'm not surprised given that they've expanded the acronym incorrectly (It should read Business Process Model and Notation)

The standard specifies: "A Message Flow MUST connect two separate Pools. They connect either to the Pool boundary or to Flow Objects within the Pool boundary. They MUST NOT connect two objects within the same Pool."  (Section 9.3, "Business Process Model and Notation" http://www.omg.org/spec/BPMN/2.0/)

Pools are just mechanisms to draw the boundaries between internal and external activities.  It doesn't necessarily map to organisations - it could be a business unit within an organisation - it's up to you how you want to separate that.  It's also up to you how you want to interpret sequence flows between lanes - to me it usually implies some sort of mechanism to notify the role that something needs their attention.

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[Will Thomas]

Hi Janelle,

Beginner or otherwise Bruce Silver's book "BPM Methods and Style with BPM Implementer's Guide" is a really great resource for modelers of all levels. On page 26 he states that messages mean any communication between the process and an external participant. Sequence flows are represented by a solid line connector and and can be drawn only within a pool. Message flows should be dashed lines with unfilled arrow heads and a little circle on the tail  can only be drawn between two pools.

Whatever tool you are using to create your models; It should be able to provide some guidance whenever you are about to save or run a check against your model.  It also helps if the s/w points to the severity of the issue, highlighting it as as either: info, warning or error. 

Some tools even let you define your own modeling guidelines to support modeling standards across the enterprise, regardless of the individual's level of modeling expertise. Its a great way to establish a quality threshold for process models no matter who creates them in the organization. Expert modeler or beginner, this feature can be a big help in creating good models.

Here are some modeling guidelines that you might also find helpful. http://www.modeling-guidelines.org/guidelines/usage-of-the-defined-edge-direction-of-message-flows/

Best,

Will

[Janelle Carter]

Thanks David, that clears it up for me!

[Neal McWhorter]

You're definitely right that this is confusing since the standard is clear that message flows must from one pool to another. I imagine if you email Dan with your question that he would be able to explain what he was thinking since he clearly knows the standard. 

In reference to David's comment about the meaning of the BPMN acronym. The original meaning what the Business Process Modeling Notation which is what it was called when BPMI handled it over the the OMG. That's what Dan is referring to.

Neal McWhorter

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[David Sanders]

The modelling tool should actually automatically infer the connection type depending on the context.  Take my modeller, Rigrr, you can only drag connections onto the canvas and the type is determined by the modeller.

If you try to connect 2 tasks in separate pools then it automatically changes to a message flow.  Same goes for connecting a sequence flow between a task and a data object - it automatically converts to a data flow.

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[Diovani Merlo]

Hi.

Message flow only is possible between pools. The presentation is incorrect or represent only visual message between edge elements.

Regards,

Diovani

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