[ogsa-dmi-wg] DMI Factory Concern

[Allen Luniewski]

I have read through the current draft of the specification.  My big 
concern after reading this is the way in which a DMI factory is going to 
get its job done.

Consider what a factory has to do.  It is given a source, S0, and a sink, 
S1, to move data between, as well as other important information.  But 
let's concentrate on the source and sink aspects at this point. The 
factory also support doing transfers using one or more transfer 
mechanisms/protocols, call them P0...PN.  The fundamental problem facing 
the factory is to find which of the Pi are supported by both S0 and S1 and 
which will meet the QoS goals of the transfer.  I am struggling to 
understand how the factory can find which of the Pi are mutually 
supported.  The current specification provides no architected mechanism 
for making this determination.

With no architected mechanism, the factory must have a means, presumably 
specific to each Pi, of asking S0 and S1 if they support Pi.  I suppose 
that this is a solution but doesn't it then place a requirement on the 
specification of each possible transfer mechanism to provide such an 
interface?  Do all transfer mechanisms have this, especially those already 
with approved specifications or, even, de facto specifications?

Another approach would be for the factory to run through the Pi trying to 
create a transfer using that Pi.  Possible, does not add additional 
requirements on the specifications of transfer protocols but it sure seems 
inefficient to me.

Is there some other way of doing this without placing something in the DMI 
spec?

In the Data Architecture document 
(http://forge.ogf.org/sf/go/doc14053?nav=1) we explicitly attacked this 
problem. We proposed a simple interface provided by each data service that 
allows the DMI factory to get a list of the transfer protocols supported 
by that service.  This seemed to us to be simple to specify, effective in 
solving the problem and easy to implement in a data service.  I suggest 
that DMI take this approach and architect such an inquiry interface 
between DMI factories and sources/sinks.

Comments?  Suggestions?

Allen Luniewski
IBM Cross Brand Services
IBM Silicon Valley Laboratory
555 Bailey Ave.
San Jose, CA 95141

408-463-2255
408-930-1844 (mobile)
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