[Myexperiment-discuss] On using an automatic workflow optimizer

[Efthymia Tsamoura]

Hello

I am a phd student and during this period i am dealing with workflow  
optimization problems in distributed environments. I would like to  
ask, if there are exist any cases where if the order of task  
invocation in a scientific workflow changes its performance changes  
too without, however, affecting the produced results. In the  
following, a present a small use case of the problem i am interested in:

Suppose that a company wants to obtain a list of email addresses of  
potential customers selecting only those who have a good payment  
history for at least one card and a credit rating above some  
threshold. The company has the right to use the following web services

WS1 : SSN id (ssn, threshold) -> credit rating (cr)
WS2 : SSN id (ssn) -> credit card numbers (ccn)
WS3 : card number (ccn, good) -> good history (gph)
WS4 : SSN id (ssn) -> email addresses (ea)

The input data containing customer identifiers (ssn) and other  
relevant information is stored in a local data resource. Two possible  
web service linear workflows that can be formed to process the input  
data using the above services are C1 = WS2,WS3,WS1,WS4 and C2 =  
WS1,WS2,WS3,WS4. In the first workflow, first, the customers having a  
good payment history are initially selected (WS2,WS3), and then, the  
remaining customers whose credit history is below some threshold are  
filtered out (through WS1). The C2 workflow performs the same tasks in  
a reverse order. The above linear workflows may have different  
performance; if WS3 filters out more data than WS1, then it will be  
more beneficial to invoke WS3 before WS1 in order for the subsequent  
web services in the workflow to process less data.

It would be very useful to know if there exist similar scientific  
workflow examples (where users have many options for ordering the  
workflow tasks but cannot decide which task ordering to use, while the  
workflow performance depends on the workflow task invocation order). I  
am asking because i have recently developed an optimization algorithm  
for this problem and i would like to test its performance in a  
real-world workflow management system (e.g., taverna) with real-world  
workflows.

P.S.: references to publications or any other information  
motivating/presenting scientific workflows of the above rationale will  
be extremely useful.

Thank you very much for your time