Hello,
Please, I would like to know the execution time of every task in the workflow (after execution).
I find, in the log file (.xes), an attribute named timestamp. But, I didn't understand its significance and if it has a relation with the execution time of a task.
Thank you for answering me.

We have logs with start and complete - see below. They are produced by YAWL and can be downloaded in the control centre. These are evaluated by tools like ProM or Disco.

    <event>
      <date key="time:timestamp" value="2015-05-15T09:56:32.419+0200"/>
      <string key="concept:name" value="Fill_in_equipment_rental_request"/>
      <string key="lifecycle:transition" value="start"/>
      <string key="lifecycle:instance" value="32.1"/>
      <string key="org:resource" value="PA-01a7abea-440d-487c-b869-c23a3e93bfc5"/>
      <string key="Using_Time/trigger" value="OnEnabled"/>
      <string key="Using_Time/expiry" value="PT30S"/>
    </event>
    <event>
      <date key="time:timestamp" value="2015-05-15T09:57:23.068+0200"/>
      <string key="concept:name" value="Fill_in_equipment_rental_request"/>
      <string key="lifecycle:transition" value="complete"/>
      <string key="lifecycle:instance" value="32.1"/>
      <string key="org:resource" value="PA-01a7abea-440d-487c-b869-c23a3e93bfc5"/>
      <string key="Requester" value="Willi"/>
      <date key="Start_date" value="2015-05-15T00:00:00"/>
      <date key="End_date" value="2015-05-15T00:00:00"/>
      <string key="Rental_request_description" value="Ich brauche einen Exkavator 2433"/>
      <string key="Using_Time/trigger" value="OnEnabled"/>
      <string key="Using_Time/expiry" value="PT30S"/>
    </event>
   

Thanks.
I impoterd the log file generated by YAWL in Disco.
You find attached an example. It display the execution time of tasks and the data transfer time between tasks.
Please, have you an idea if I can know the size of data transfered from a task to another ?
Thank you again.

What do you mean by size of data? Where should that come from? One way of doing this could be to include it in the variables of a task. They are included in the log like here:

<string key="Requester" value="Willi"/>

Please, I would like to know the output size of tasks (measured by megabit). This means the amount of data transferred from a task T1 to its successive task T2. Of course, this data is necessary to the execution of T2.
Also, how can I know the instruction number of every task.
I didn't understand <string key="Requester" value="Willi"/> ?

Please, I need a response.
Thank you in advance.