[SAGA-RG] Fwd (andre at merzky.net): Re: JSDL - SAGA

Fri Feb 16 06:37:40 CST 2007

Quoting [Thilo Kielmann] (Feb 16 2007):
> 
> Folks,
> 
> I think we are having conflicting goals here.
> (Technical goals, not personal ones ;-)
> 
> On one hand, we have the "S for simplicity" in SAGA, and we must keep it.
> 
> On the other hand, we have the necessity to support JSDL, future JSDL
> extensions, or any other types of job decscriptions that people want to use.
> (And still might to be invented.)

That is one of the points I kind of disagree with:  Do we
really have the necessity to support native JSDL, or even
JSDL++?

The _only_ point in our use cases where JSDL is explicitely
mentioned is the RealityGrid use case

11. Grid Technologies currently used:
-------------------------------------

  If you are currently using or developing this scenario, which
  grid technologies are you using or considering?

    Currently using: gsissh, globus-url-copy, globus-job-run,
    GSI, WSDL, Grid Services (OGSI::Lite), SOAP, XML, GridSphere,
    Access Grid, VizServer, Chromium, gsoap.

    Currently considering WS-RF, WS-Notification, WS-Security,
    SRB, JSDL, UNICORE, Sakai.

'_consider_' using JSDL, and after listing WS-RF and other
WS-Standards. 

I also think that this is the level where JSDL is aiming at:
the JSDL spec specifies the target use cases of JSDL
documents to be exchanged between WS clients and WS services
- it is, IMHO, not intended to be a human readable or API
level language (see paragraph 2,3 of introduction, and
figure 1 in the JSDL spec).

> Assume, JSDL++ (whatever it will look like in near future) will become a
> widely adopted standard. (Or anything else, doesn't matter in the following.)
> Then, SAGA implementations will have to use JSDL++, and to form JSDL++ from
> SAGA job descriptions. 

Yes, that is right.  And not a problem.

> Simultaneously, users are likely to use JSDL++
> themselves, and may wnat to use JSDL++ to express their resource needs.

That is what I doubt: users will in general NOT write XML
documents manually.  Even simple JSDL docs are not
neccessarily human readable (IMHO), and the extensions will
be, well, more interesting (from what I have seen about them
so far).  So that is why I think that...

> At this point in time, SAGA will sit in the middle, and it may be very clumsy
> to first translate from JSDL++ to a SAGA job description, and then back to
> JSDL++ somewhere "down under" in the implementation.

... this situation will be the exception, not the rule.

> For the very purpose of SAGA as a universal and simple grid API, it has to: 
> - be independent of job description standards (mostly simpler than them)

We are!  That is how our JD was derived/defined.

> - support job description standards

We do!  Our JD is easily translatable into JSDL.

> My suggestion:
> 
> SAGA should have one class of job descriptions, and the possibility to
> create subclasses for more specific job descriptions (like JSDL).
> Such subclasses could be defined as separate extension documents (just like
> gridcpr). (Or was it "resource descriptions"???)

The problem with that is that you'd allow, at some point,
also Globus-RSL job descriptions, or Naregi-RSL job
descriptions, which bind your application to the specific
back ends, and hence break portability. (BTW, I think the
number of users which would like to re-use RSL is certainly
larger than thos who want to reuse JSDL...)

> With this approach, users could still write programs that are independent
> of the underlying job submission machinery, having a simplified view on
> jobs and resource attributes etc. etc.
> At the same time, subclassed job/resource descriptions could be
> "passed through" transparently from the API to the implementeation, without
> being converted back and forth, a process that is very likely to loose some
> important details.

passing things through is a bad idea - that is what we
learned with GAT.  I hoestly think we should stay away from
that, as far as possible.  

My suggestion:

  If there emerge any use cases which are not satisfied with
  the job description we have in SAGA, then the job
  description in SAGA needs to be fixed.  And yes, we should
  make sure that this fix is translatable into JSDL, and
  possibly others.  Until we have such use cases, stay
  Simple! (i.e.  change nothing).

Cheers, Andre.

> Is this a route to go?
> 
> 
> Thilo
> 
> On Tue, Feb 13, 2007 at 06:28:58PM +0100, 'Andre Merzky' wrote:
> > From: 'Andre Merzky' <andre at merzky.net>
> > To: SAGA RG <saga-rg at ogf.org>
> > Subject: [SAGA-RG] Fwd (andre at merzky.net): Re: JSDL - SAGA
> > 
> > Hi group(s), 
> > 
> > a couple of us had a recent discussion (f2f and email) about
> > JSDL and SAGA.  The question is: should we support JSDL
> > fully on API level?  E.g., should we allow the application
> > programmer to specify/use JSDL documents for job creation?
> > 
> > The reasons for doing that are compelling: JSDL is one of
> > the most acknowledged standards in OGF, and the number of
> > backends supporting JSDL is rapidly increasing it seems.
> > Supporting JSDL directly would allow to interface with other
> > tools using JSDL, and would allow to reuse JSDL documents
> > where these are already available.
> > 
> > Well, I have however some problems with that approach, which
> > are outlined in the cited email below.
> > 
> > Do you guys have any other thoughts, and what solution would
> > you prefer?
> > 
> > Cheers, Andre.
> > 
> > 
> > ----- Forwarded message from 'Andre Merzky' <andre at merzky.net> -----
> > 
> > > From: 'Andre Merzky' <andre at merzky.net>
> > > To: Shantenu Jha <sjha at cct.lsu.edu>
> > > Cc: Hartmut Kaiser <hkaiser at cct.lsu.edu>,
> > > 	'Thilo Kielmann' <kielmann at cs.vu.nl>,
> > > 	'Andre Merzky' <andre at merzky.net>
> > > Subject: Re: JSDL - SAGA
> > > 
> > > Hartmut and I discussed that somewhat last week.  So he
> > > knows I am not wholehartedly for that option.  SAGA is
> > > supposed to abstract the low level details, not to expose
> > > them.
> > > 
> > > JSDL is going to define a number of extensions now.  Some of
> > > these extensions are very useful for us, others not.
> > > Mostly, they will be more complex than JSDL itself.
> > > 
> > > Are we going to support the extensions?  Which?  All/some?
> > > How to select?  What error do we report on unsupported
> > > extensions?  Do we mandate that extensions are supported by
> > > the backends?  Which?
> > > 
> > > Even w/o extensions: is the job description updated after an
> > > JSDL attrib is set?  What about those attribs which are not
> > > JSDL keys?  Assume an implementation which implements the
> > > existing SAGA job description keys: MUST it support complete
> > > JSDL now?  What error whould it report?
> > > 
> > > These are probably all solvable problems, and I do agree
> > > that there are advantages, i.e. the re-use of existing JSDL
> > > documents.  Anyway, IMHO we should be careful, consider if
> > > we really have enough use cases etc.  Also, a free function
> > > jsdl_to_job_description may do the trick, w/o complicating
> > > the job package itself.
> > > 
> > > Cheers, Andre.
> > > 
> > 
> > Another point I'd like to raise is: if HPC profile bekomes a
> > widely accepted OGF standard, do we support it directly,
> > too?  Or OGSA-Workflow?  Where to stop, and where is the 'S'
> > in that approach?
> > 
> > Andre.
> > 
> > 
> > > Quoting [Shantenu Jha]
> > >> 
> > >> What little I know, I think so to.
> > >> 
> > >>
> > >> Quoting [Hartmut Kaiser]
> > >>>
> > >>> Agree 100%
> > >>> The easiest way is probably just to add a attribute in the job description
> > >>> taking the whole JSDL.
> > >>>
> > >>
> > >> Quoting [Thilo Kielmann]
> > >>>
> > >>> Yes!
> > >>>
> > >>> 
> > >>> Quoting [Shantenu Jha]
> > >>>>
> > >>>> Shouldn't we ensure that SAGA consumes JSDL w/o any
> > >>>> problem/changes?
> > >>>>
> > -- 
> > "So much time, so little to do..."  -- Garfield
> > --
> >   saga-rg mailing list
> >   saga-rg at ogf.org
> >   http://www.ogf.org/mailman/listinfo/saga-rg
-- 
"So much time, so little to do..."  -- Garfield