[Pgi-wg] OGF PGI Requirements - Flexibility and clarity versus Rigidity and confusion

Fri Apr 30 15:22:13 CDT 2010

Hi Etienne,

I have a feeling that there is sometimes a tendency to overcomplicate simple things.

You are right in saying that many requirements are formulated in a confusing manner.

In fact, it is very difficult to formulate a requirement or a definition. It is like describing a face. You often feel like "I recognize it when I see it, but can't describe".

With unclear "requirements" one has to understand what *is* the requirement.  And to do this, one has to understand the use case.

Take your example of "scalable time". The use case is trivial: it makes *no sense whatsoever* to specify either CPU time or wallclock time in a heterogeneous system. Because there are different hardwares around. You *have* to characterize hardware on which this performance was achieved. Period. I hate the word "scalable" here because it really steels all attention, hinting at implementation details. Who said that execution time scales lineraly with benchmark values anyway? This is the real requirement:

*** It must be possible to specify hardware characteristics (e.g. in terms of a benchmark value) corresponding to the indicated performance numbers ***

And mind it, performance numbers in general are not limited to time. It might be also memory consumption from another foggy requirement of ours: it obviously will be different on 32- and 64-bit architectures.

How will the tools use this information, is a different question.

Cheers,
Oxana

2010-04-30 17:24, Etienne URBAH пишет:
> Balazs, Morris, Luigi, Johannes and all,
>
>
> Concerning the capture and discussion of the requirements :
>
>
> I think that the main problem is NOT the large number of requirements,
> but the fact that many original requirements were formulated in a very
> confusing manner.
>
> In particular, many original requirements simultaneously present :
> A) mainly, the WAY the Execution Service would perform a desired
> functionality,
> B) sometimes, the INTERFACE which a Client would use to access this
> functionality,
> C) implicitly, the NEED for this functionality.
>
> This causes us to lose much time in useless discussions, because this
> requires to use following process :
> - First, focus on C) to precisely define the functionality, and assess
> its usefulness,
> - Second, focus on B) to define the Client interface,
> - Third, verify that there is no garbage from A) left anymore.
>
> Working on the original explicit, implicit or hidden requirements found
> inside the documents, this is exactly the process which I personally
> followed, splitting complex confusing requirements into simpler and
> clearer ones.
> This permitted that requirements which I personally wrote down could be
> often quickly understood, discussed, and even sometimes quickly labeled
> YES (positively agreed) or NO (No agreement yet).
>
>
> For the many requirements which are still unclear, I therefore urge you
> to accept that I split them into simpler smaller requirements :
>
> - Apparently, it will increase the total number of requirements,
>
> - But in fact, after an easy work, that will increase the percentage of
> requirements labeled YES and diminish the percentage of requirements
> labeled UNCLEAR.
>
>
> As example, please study following requirement, labeled 'Still UNCLEAR
> after 10 mn discussion' :
>
> - JD20 (115) Job Description document should offer a new re-usable
> structure to define 'scalabletime' requests optionally depending on
> benchmark results.
>
>
> I will split it into the 4 following requirements :
>
>
> - Description of the needed functionality :
>
> JD20.1 For 'Wall clock time' and 'CPU time' limits, the Execution
> Service SHOULD accept Client requirements independently of the speed of
> the Computing Resource on which the Activity will run
>
>
> - Description of the conceptual Client interface :
>
> JD20.2 For 'Wall clock time' and 'CPU time' limits, the Job Description
> document SHOULD offer a new re-usable structure permitting to describe
> requirements independently of the speed of the Computing Resource on
> which the Activity will run
>
>
> - First option for a precise description of the Client interface :
>
> JD20.3 For 'Wall clock time' and 'CPU time' limits, the re-usable
> structure permitting to describe requirements independently of the speed
> of the computing resource on which the Activity will run SHOULD be the
> ordered pair (Value, Unit) where :
> - 'Value' is the max number of operations allowed for the Activity,
> - 'Unit' is as unit suitable for a total number of operations, from a
> closed list to be refined (such as 'Specint2006 * hours' or 'Billions of
> floating point operations')
> This method is already used by BOINC and has proved it robustness.
>
>
> - Second option for a precise description of the Client interface :
>
> JD20.4 For 'Wall clock time' and 'CPU time' limits, the re-usable
> structure permitting to describe requirements independently of the speed
> of the computing resource on which the Activity will run SHOULD be a
> 'scalabletime' specified by a (Value, BenchmarkType, BenchmarkValue)
> triplet as described in chapter 7.2 of the Specification Draft
>
>
> I am absolutely certain that these 4 simple requirements will be quickly
> understood.
> I am quite sure that we will immediately obtain a YES for JD20.1 and
> JD20.2, and perhaps quickly a YES to either JD20.3 or JD20.4 (and a NO
> to the other one).
>
>
> In the same way of thinking, I will re-propose following dropped
> requirements. With sometimes an improved title, they describe the NEED
> for a precise Client interface, WITHOUT specifying the precise component
> which will implement them :
>
> - IS10 For requests querying Status of finished Activity, the
> Information functionality MUST accept, as input parameter, 1 Activity ID
>
> - IS12 For requests querying Activity Status, the Information
> functionality MUST accept, as input parameter, complex queries on
> Activities expressed according to the GLUE2 model without explicit
> specification of the Activity IDs. The Information functionality MAY
> support multiple query languages in addition to the mandatory one.
>
> - LB4 For all requests, the Query functionality for Activity Logs MUST
> accept, as input parameter, 1 Activity ID
>
> - LB6 For all requests, the Query functionality for Activity Logs MUST
> accept, as input parameter, complex queries on Activities expressed
> according to the GLUE model without explicit specification of the
> Activity IDs. The Logging and Bookkeeping functionality MAY support
> multiple query languages in addition to the mandatory one.
>
>
> Besides, I just detected that we forgot to study following requirement,
> which was mentioned in my mail dated 26 April 2010. Is it possible to
> associate spreadsheet ID 172 to it ?
>
> - IS14 In order to prevent overloading the Execution Service (which has
> performance requirements for Activity Management), the Information
> functionality SHOULD be separated from the Execution Service
>
>
> Thank you in advance for accepting that, when starting with original
> confusion :
> - rigidity prevents improvement and favors endless confusion,
> - flexibility favors improvement and then clarity.
>
>
> Best regards.
>
> -----------------------------------------------------
> Etienne URBAH LAL, Univ Paris-Sud, IN2P3/CNRS
> Bat 200 91898 ORSAY France
> Tel: +33 1 64 46 84 87 Skype: etienne.urbah
> Mob: +33 6 22 30 53 27 mailto:urbah at lal.in2p3.fr
> -----------------------------------------------------
>
>
>
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