OGF-19 Report
Omer Rana – GridNet ID: 107
o.f.rana@cs.cardiff.ac.uk
Cardiff School of Computer Science/Welsh eScience Centre
February 4, 2006
The Open Grid Forum (OGF-19) took place at the Friday Center (at RaleighDurham, North Carolina). I attended the event from January 28 to February
2. I participated in:
• The GRAAP working group, focusing on WS-Agreement specification.
• The Semantic Web workshop—organized by Dave de Roure and Carole
Goble.
• The OGSA group—particularly the workflow and information model discussion.
• The Quality of Service BoF—organized by Steve McGough.
• The workshop on Reliability and Dependability—organized by Chris Dubrowski
and Geoffrey Fox.
• The Software Providers tracks on OMII and Grid Sphere.
1
GRAAP Working Group
Although three sessions were scheduled for the GRAAP working group, we were
able to resolve outstanding issues in two sessions. The first session focused on
public comments that had been received on the WS-Agreement specification.
Wolfgang Ziegler flagged the issues and identified how these were being addressed in the updated specification. It was expected that the specification
document would be modified to reflect these comments within the next 4 weeks.
There was also discussion about WS-Agreement interoperability, and which
aspects of interoperability would be most useful to demonstrate across different
WS-Agreement implementations. It was generally agreed that interoperability
at the level of the protocol was too simple. A teleconference has been scheduled
for February 16 between individuals/groups involved in the implementation of
the WS-Agreement specification. Participants from the Fraunhofer Institute,
Cardiff University, Juelich Research Center and University of Paderborn would
be invited to participate in the teleconference. Based on feedback from the OGF
area directors, it was identified that an information document (that would be
reviewed) would be needed to outline the operations that would be involved in
the interoperability test(s).
1
There was also discussion about the general area of dynamic SLAs, and identifying precisely what was implied by this term. For instance, many coming to
WS-Agreement sessions in the past have identified the need for including negotiation within the WS-Agreement specification. However, it was, once again,
generally agreed that negotiation was too complex to support in the current
version of the specification. It was proposed that perhaps the group should consider “negotiation profiles” – similar to the HPC profile that had been proposed
by other groups at OGF. This was found to be a useful middle option, and this
aspect would be considered at a future session.
2
Semantic Web Workshop
The Semantic Web 2.0 workshop focused on two main themes: (i) usability
issues associated with existing eScience software; (ii) how emerging themes such
as “mashups” and “gadgets” (from Google) could be used to support dynamic
user interfaces.
A tutorial by Pamela Fox and Marlon Pierce on “mashups” and Web 2.0
technologies identified the ease of creating a mashup using the Google API—the
tutorial stressed how this approach could be used to provide quick prototypes.
It was recognized that there were too many Web Services (WS-*) standards
currently in existence, and it was often hard to identify how they related to
each other. It was also difficult for new programmer to decide which of these
to focus on. Marlon Pierce demonstrated the use of the Google maps API,
and how additional data could be combined with the maps provided by Google.
Geoffrey Fox also indicated that mashups were similar to workflows – as they
involved integration of a number of capabilities to generate an output – which
could then be displayed through a Web browser. I disagree with this view, for
the following reasons: (i) a mashup may involve combining capabilities of a
number of services (in this sense, they are somewhat similar to the outcome of a
workflow process), however, the actual process involved that has been involved
is never fully exposed (unlike a workflow); (ii) workflows involve a combination
of different control strategies that indicate how service interaction should take
place. Often, this control flow is also exposed to some enactment tool. In a
mashup, this is not undertaken.
This workshop provided a good discussion of semantic Web technologies that
could be used to develop user interfaces for scientists. The relationship between
mashups and Portals was not fully explored — although these seem to be (at a
first glance) complementary technologies.
3
OGSA Workflow and Information Model Discussion
The OGSA information model working group discussion focused mainly on the
use of XQuery over JSDL and BES documents. The work in this group is
2
rather sluggish at present, although good overall progress is being made by
Ellen Stokes. It is not immediately clear, however, what additional benefit
the approach being proposed in this group offers above Condor ClassAds and
the Redline System from Argonne. In additional, significant work in semantic
matchmaking is being ignored by the group—especially work undertaken in the
multi-agent systems community.
It was also recognized that there was a need to support workflow descriptions in the OGSA architecture. The OGSA workflow discussion was led by
Andrew Grimshaw (University of Virginia). The discussion was primarily focused on whether it was necessary to extend OGSA with workflow descriptions,
or whether the group should interact with other external work (a significant
amount of which already exists!). The need for workflow was based on the
inability, at present, to identify job dependencies in OGSA. A middle ground
was advocated—with multiple groups identified to carry out the following tasks:
(i) identify what was already in existence; (ii) explore what extensions would
be necessary to support workflow in OGSA; and (iii) investigate what types of
workflow would be useful to see in OGSA. Cardiff will be participating in aspect
(i).
4
Quality of Service BoF
The QoS BoF was organized due to a number of requests at OGSA working
group sessions in the past. Many people had expressed an interest in providing
a more concise view of QoS. The QoS BoF consisted of three talks: (i) the use
of QoS metrics to support replica management (XXX, University of Virgina);
(ii) the G-QoSM project—identifying relationship between QoS metrics and
Service Level Agreements (Omer Rana); and (iii) the use of QoS in the GridCC
project (Steve McGough, Imperial College). The subsequent discussion focused
on providing a more concise definition of QoS. Many at the BoF were concerned
that a more precise list of metrics that could be associated with QoS were
required, and often the distinction between QoS and an SLA was not clear.
Members of the networks community present at the BoF identified that QoS
had well defined semantics in the context of network applications (focusing on
bandwidth, latency, packet delay and packet jitter)—and that similarly, the Grid
community should consider the end-to-end QoS that could aggregate quality
metrics across an application, middleware and the network layers. It was agreed
that to keep the task manageable, a focus on QoS metrics associated with the
OGSA would be a useful starting point.
5
Reliability and Dependability Workshop
The Reliability and Dependability workshop was focused on: (i) providing a
more precise view on reliability issues in the context of Grid applications; (ii)
mechanisms that could be used to adapt the underlying infrastructure to sup-
3
port reliability. The workshop consisted of a number of talks from academic
researchers and infrastructure providers outlining what they considered to be
reliability issues, and their particular perspectives on supporting a more adaptive infrastructure.
A common theme in many of the talks was the ability to monitor running
applications for “exceptional” behaviour, and using actuation mechanisms to:
(i) re-schedule; (ii) re-start or (iii) terminate error prone applications. The
actuation approaches were primarily based on feedback control system ideas—
whereby a change in system state from some ideal would be monitored, and the
system “pushed” to move towards this “ideal” (or “controllable”) state. Example traces from an application executed over the TeraGrid was used to demonstrate the ideas. It was interesting to see many similarities between the techniques being discussed by the authors and approaches being advocated within
the Autonomic Computing community. It was generally recognized, however,
that supporting suitable actuation was a difficult process in a distributed environment.
6
Software Providers Track – OMII and GridSphere
The Software Providers track was being introduced at the OGF for the first
time. It was a very useful introduction to internal of many software libraries for
Grid computing. The OMII track primarily focused on the OMII projects that
are now available for use (such as OGSA-DAI, GRIMOIRES, etc) and newly
funded projects that are expected to deliver over the next year.
The GridSphere session focused on changes that have been made to the
GridSphere Portal Development Tools, and introduced the Vines software that
will provide an API that can be used alongside GridSphere. The Vines API
can be used in a standalone mode, and could provide capability that could be
integrated with user applications.
7
Next Steps
As a next step to my participation at the OGF, the following proposals have
been made to continue this work:
• A telecon. has been organized for February 16, 2007, to focus on discussing interoperability tests that need to be carried out between two (or
more) WS-Agreement implementations. This telecon. has been intended
to define the basis for an information document on WS-Agreement interoperability.
• A workshop at the National eScience Center in Edinburgh on February 19
and 20 with a particular focus on “Agent-based Grid Computing”. Service
4
Level Agreements will form one of the key topics of discussion. The workshop is funded by the EPSRC “Agentcities.UK” network—with secretarial
support from NeSC. This workshop is jointly organized by Julian Padget
(Bath University) and me. Members of the Semantic Web community
(such as researchers in the EU TrustCom, EU OntoGrid, OMII Knoogle,
EPSRC DiscoveryNet, EU SORMA, EU Catnets and EU BREIN projects)
will be participating in the workshop). The event is therefore also intended
to provide cross fertilization between Semantic Grids and SLAs.
• A workshop has been proposed at OGF20 in Manchester (in May 2007) –
consisting of two 90-minute sessions. The focus at this workshop will be on
“Dynamic Service Level Agreements”. This workshop is to be jointly organized by Wolfgang Ziegler (Fraunhofer Institute), Philipp Weider (Jeulich
Research Center) and me.
• A workshop at the IEEE/ACM “Autonomic Computing” conference at
Jacksonville (Florida) on “Policy-based Autonomic Computing”. A key
theme in this workshop is the relationship between policy specification and
Service Level Agreements. The workshop is jointly organized by Richard
Anthony (University of Greenwich), Duncan Johnston-Watt (Enigmatec
Corporation) and me.
• There will be a tutorial at the IEEE CCGrid 2007 conference in Rio de
Jenairo (Brazil) in May 2007. The tutorial is focused on “Autonomic Grid
Computing” and will be delivered by Salim Hariri (University of Arizona),
Manish Parashar (Rutgers University) and me. Over 20% of the tutorial
will be dedicated to Service Level Agreements.
5