BPMI.org

[Alam]

Hi,

I have some doubts related to gates.

Inclusive Gateways (OR)
1) Supose I use two gates after inclusive gate and in certain condition both becomes true. In that case does token will flow from both the gates.

1) If I use Inclusive Or gate for split and again I want to merge all the alternative paths then which gate should I use ( OR Gate or XOR gate).

XOR Gate
1) If I use Event based XOR gate for split and again I want to merge all the alternative paths then which gate should I use. In this case can I use AND gate. If yes then how the gate will synchronize all the tokens flowing from alternative paths as token will pass only from one path i.e. true condition gate.

Please help me out in clearing these doubts,

thanks

[axw-casenove]

Hi Alam,

The Inclusive Gateway will activate all gates with a valid condition. So if you have several gates with a true condition, a token will flow from each of these gates, that's right.

To merge paths resulting from an Inclusive Gateway, BPMN say you can use an Inclusive Gateway, because it will wait for all tokens generated upstream (it's a bit confusing for me in fact). So for example, if 2 tokens of 3 are generated from an Inclusive Gateway, the second Inclusive Gateway used to merge the paths will wait for these 2 tokens instead of 3...

The Exclusive Gateway accepts only one token from a same set. (see p 133). When the first token arrives, it will pass immediately through the gateway, without waiting for other tokens. So you can't use this gateway for synchronization.

When you use the Exclusive Gateway for split, then only one path is actived by definition. You can't use the Parallel Gateway (AND) to merge the paths because it will wait undefinitely for other paths that will never be activated. You can use the Exclusive gateway instead, it will let the token pass as soon as it arrives.

Hope it is helpfull,

Cédric Casenove

[masood]

Hi casenove,

The above doubts also came in mind when I was surfing the below site.

www.tmitwww.tm.tue.nl/research/ patterns/download/BPMN-pat.pdf

IN WP-10 (Sycronizing Merge) an OR gate is used for split and XOR for Merge.

IN WP-18 (Interleaved Routing) an event based OR gate is used for split and AND gate is used for Merge.

Please go through the above mentioned link.

[masood]

Sorry,

the link is

http://tmitwww.tm.tue.nl/research/patterns/download/BPMN-pat.pdf

masood

[axw-casenove]

I think the patterns described in the document above are correct.

In WP-10 version 1, it doesn't matter if one or two paths are activated after the Inclusive Gateway. The Exclusive Gateway will accept the first token that arrives and execute task D immediately. If another token arrives later, it will be stopped at the Exclusive Gateway.
The difference between version 1 and 2 is that a synchronization can happen on the second Inclusive Gateway of version 2.

In WP-18, we are sure that Task F and Task G will be executed (only one path is chosen after Exclusive Gateway but the other path is followed by the conditional sequence flow), so we can use a Parallel Gateway to merge the paths.

Any type of gateway can be used to split or merge path, depending on what the process is intended to do.

[masood]

Hi casenove,

WP-10 is now clear but in WP-18 is still some doubts are there. What you are saying is right for Activity F and G but what about activity B and C which are starting after activity A. These activities are starting after Exclusive (Event Based) Gate which will decide only one path (based on the event) i.e. the token will take path of B or C and not of both. In that case the "And gate" will wait for another token which is not coming in this case. Please clear my this doubt.

Masood

[axw-casenove]

Hi,

Sorry, I didn't look at the left part of the graph... Well if it's really an Exclusive Gateway that is used to split the paths, then in my opinion the process can't work The first Parallel Gateway will never receive the two tokens needed...

But perhaps the graph is correct and I am wrong, how knows !

[Stephen A White]

The version of WP18 shown at
http://tmitwww.tm.tue.nl/research/patterns/download/BPMN-pat.pdf
is an old version of this pattern and doesn't work.

A newer and more accurate version of WP18 can be found here:

http://www.bpmn.org/Samples/Patterns/interleavedRouting.htm

-Steve