An Open Grid Services
Architecture
Steve Tuecke
Argonne National Laboratory
Globus Project™
http://www.globus.org
Partial Acknowledgements
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Open Grid Services Architecture work is
performed in collaboration with
– Ian Foster, Globus Co-PI @ ANL & UC
– Carl Kesselman, Globus Co-PI @ USC/ISI
– Steve Tuecke, Globus Toolkit Architect @ANL
– Jeff Nick, Steve Graham, Jeff Frey @ IBM
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Globus Toolkit R&D also involves many fine
scientists & engineers at ANL, USC/ISI, and
elsewhere (see www.globus.org)
Strong collaborations with many outstanding
EU, UK, US Grid projects
Support from DOE, NASA, NSF, Microsoft
February 7, 2002
Open Grid Services Architecture
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Grid Computing
February 7, 2002
Open Grid Services Architecture
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Overview
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The universal nature of the “Grid problem”
A review & assessment of Grid technologies,
in particular the Globus Toolkit™
Open Grid Services Architecture as an
evolution & integration of Grid technologies
and Web services
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Open Grid Services Architecture
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The Grid Problem
Resource sharing & coordinated problem
solving in dynamic, multi-institutional
virtual organizations
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Open Grid Services Architecture
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Why Grids? (1) eScience
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A biochemist exploits 10,000 computers to
screen 100,000 compounds in an hour
1,000 physicists worldwide pool resources
for peta-op analyses of petabytes of data
Civil engineers collaborate to design,
execute, & analyze shake table experiments
Climate scientists visualize, annotate, &
analyze terabyte simulation datasets
An emergency response team couples real
time data, weather model, population data
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Open Grid Services Architecture
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Grid Communities & Applications:
Data Grids for High Energy Physics
~PBytes/sec
Online System
~100 MBytes/sec
~20 TIPS
There are 100 “triggers” per second
Each triggered event is ~1 MByte in size
~622 Mbits/sec
or Air Freight (deprecated)
France Regional
Centre
SpecInt95 equivalents
Offline Processor Farm
There is a “bunch crossing” every 25 nsecs.
Tier 1
1 TIPS is approximately 25,000
Tier 0
Germany Regional
Centre
~100 MBytes/sec
CERN Computer Centre
Italy Regional
Centre
FermiLab ~4 TIPS
~622 Mbits/sec
Tier 2
~622 Mbits/sec
Institute
Institute Institute
~0.25TIPS
Physics data cache
Institute
~1 MBytes/sec
Tier 4
Caltech
~1 TIPS
Tier2 Centre
Tier2 Centre
Tier2 Centre
Tier2 Centre
~1 TIPS ~1 TIPS ~1 TIPS ~1 TIPS
Physicists work on analysis “channels”.
Each institute will have ~10 physicists working on one or more
channels; data for these channels should be cached by the
institute server
Physicist workstations
www.griphyn.org
February 7, 2002
www.ppdg.net
Open
Grid Services Architecture
www.eu-datagrid.org
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Grid Communities and Applications:
Network for Earthquake Eng. Simulation
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NEESgrid: US national
infrastructure to couple
earthquake engineers
with experimental
facilities, databases,
computers, & each other
On-demand access to
experiments, data
streams, computing,
archives, collaboration
NEESgrid:
Argonne, Michigan,
UIUC, USC
February 7, 2002
Open Grid NCSA,
Services Architecture
www.neesgrid.org
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Why Grids? (2) eBusiness
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Engineers at a multinational company
collaborate on the design of a new product
A multidisciplinary analysis in aerospace
couples code and data in four companies
An insurance company mines data from
partner hospitals for fraud detection
An application service provider offloads
excess load to a compute cycle provider
An enterprise configures internal & external
resources to support eBusiness workload
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Open Grid Services Architecture
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Intelligent Infrastructure:
Distributed Servers and Services
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Grids: Why Now?
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Moore’s law ⇒ highly functional end-systems
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Ubiquitous Internet ⇒ universal connectivity
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Network exponentials produce dramatic
changes in geometry and geography
– 9-month doubling: double Moore’s law!
– 1986-2001: x340,000; 2001-2010: x4000?
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New modes of working and problem solving
emphasize teamwork, computation
New business models and technologies
facilitate outsourcing
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Elements of the Problem
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Resource sharing
– Computers, storage, sensors, networks, …
– Heterogeneity of device, mechanism, policy
– Sharing conditional: negotiation, payment, …
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Coordinated problem solving
– Integration of distributed resources
– Compound quality of service requirements
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Dynamic, multi-institutional virtual orgs
– Dynamic overlays on classic org structures
– Map to underlying control mechanisms
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The Grid World: Current Status
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Dozens of major Grid projects in scientific &
technical computing/research & education
– Deployment, application, technology
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Considerable consensus on key concepts
and technologies
– Open source Globus Toolkit™ a de facto
standard for major protocols & services
– Far from complete or perfect, but out there,
evolving rapidly, and large tool/user base
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Global Grid Forum a significant force
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Industrial interest emerging rapidly
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Open Grid Services Architecture
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The Globus Toolkit in One Slide
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Grid protocols (GSI, GRAM, …) enable resource
sharing within virtual orgs; toolkit provides reference
implementation ( = Globus Toolkit services)
MDS-2
(Meta Directory Service)
Reliable
remote
GSI User
invocation Gatekeeper Reporter
(Grid
(registry +
Authenticate &
(factory)
discovery)
Security create proxy
Create process Register
Infrastruc- credential
ture)
User
process #1
Proxy
User
process #2
Proxy #2
Other GSIauthenticated
remote service
requests
GRAM
(Grid Resource Allocation & Management)
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Soft state
registration;
enquiry
GIIS: Grid
Information
Index Server
(discovery)
Other service
(e.g. GridFTP)
Protocols (and APIs) enable other tools and services
for membership, discovery, data mgmt, workflow, …
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Open Grid Services Architecture
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Globus Toolkit: Evaluation (+)
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Good technical solutions for key problems, e.g.
– Authentication and authorization
– Resource discovery and monitoring
– Reliable remote service invocation
– High-performance remote data access
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This + good engineering is enabling progress
– Good quality reference implementation, multilanguage support, interfaces to many systems,
large user base, industrial support
– Growing community code base built on tools
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Open Grid Services Architecture
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Globus Toolkit: Evaluation (-)
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Protocol deficiencies, e.g.
– Heterogeneous basis: HTTP, LDAP, FTP
– No standard means of invocation, notification,
error propagation, authorization, termination, …
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Significant missing functionality, e.g.
– Databases, sensors, instruments, workflow, …
– Virtualization of end systems (hosting envs.)
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Little work on total system properties, e.g.
– Dependability, end-to-end QoS, …
– Reasoning about system properties
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“Web Services”
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Increasingly popular standards-based
framework for accessing network applications
– W3C standardization; Microsoft, IBM, Sun, others
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WSDL: Web Services Description Language
– Interface Definition Language for Web services
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SOAP: Simple Object Access Protocol
– XML-based RPC protocol; common WSDL target
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WS-Inspection
– Conventions for locating service descriptions
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UDDI: Universal Desc., Discovery, & Integration
– Directory for Web services
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Open Grid Services Architecture
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Transient Service Instances
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“Web services” address discovery & invocation
of persistent services
– Interface to persistent state of entire enterprise
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In Grids, must also support transient service
instances, created/destroyed dynamically
– Interfaces to the states of distributed activities
– E.g. workflow, video conf., dist. data analysis
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Significant implications for how services are
managed, named, discovered, and used
– In fact, much of our work is concerned with the
management of service instances
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Open Grid Services Architecture
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Open Grid Services Architecture
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Service orientation to virtualize resources
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From Web services:
– Standard interface definition mechanisms:
multiple protocol bindings, multiple
implementations, local/remote transparency
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Building on Globus Toolkit:
– Grid service: semantics for service interactions
– Management of transient instances (& state)
– Factory, Registry, Discovery, other services
– Reliable and secure transport
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Multiple hosting targets: J2EE, .NET, “C”, …
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OGSA Service Model
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System comprises (a typically few) persistent
services & (potentially many) transient services
All services adhere to specified Grid service
interfaces and behaviors
– Reliable invocation, lifetime management,
discovery, authorization, notification,
upgradeability, concurrency, manageability
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Interfaces for managing Grid service instances
– Factory, registry, discovery, lifetime, etc.
=> Reliable, secure mgmt of distributed state
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The Grid Service
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A (potentially transient) Web service with
specified interfaces & behaviors, including
– Creation (Factory)
– Global naming (GSH) & references (GSR)
– Lifetime management
– Registration & Discovery
– Authorization
– Notification
– Concurrency
– Manageability
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Open Grid Services Architecture
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Factory
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A Grid service with Factory interface can
be requested to create a new Grid service
instance
– Reliable creation (once-and-only-once)
– Create operation can be extended to accept
Grid service specific creation parameters
– Returns a Grid Service Handle (GSH)
> A globally unique URL
> Uniquely identifies the instance for all time
> Based on name of a home mapper service
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Mapper
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A GSH is a stable name for a Grid service, but
does not allow client to actually communicate
with the Grid service
A Grid Service Reference (GSR) is a WSDL
document that describes how to communicate
with the Grid service
– Contains protocol binding, network address, …
– May expire (I.e. GSR information may change)
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The Mapper interface allows a client to map
from a GSH to a GSR
– http get on GSH also returns a GSR
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Open Grid Services Architecture
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Lifetime Management
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GS instances created by factory or manually;
destroyed explicitly or via soft state
– Negotiation of initial lifetime with Factory
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SoftStateDestruction interface supports
– GetTerminationTime message for inquiry
> Notification interface also allows for lifetime notification
– SetTerminationTime message for keepalive
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Soft state lifetime management avoids
– Explicit client teardown of complex state
– Resource “leaks” in hosting environments
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ExplicitDestruction interface also available
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Discovery
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A Grid service instance may maintain a set
of service information
– XML fragments encapsulated in standard
<name, type, TTL-info> containers
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Discovery interface allows clients to query
the Grid service instance for this information
– Query operation, plus supporting operations
> Extensible query language support
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See also Notification interfaces
– Allows notification of service existence and
about service information
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Registry
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The Registry interface may be used to discover a
set of Grid service instances
– Returns a WS-Inspection document containing the
GSHs of a set of Grid services
– Also returns policy associated with the set
– Also available through Discovery interface
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The RegistryManagement interface allows for softstate registration of a Grid service
– A set of Grid services can periodically register their
GSHs into a registry service, to allow for discovery of
services in that set
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Authorization
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Protocol binding handles authentication during
invocation of Grid service operation
– Gives service URI for authenticated subject
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Grid service instance should apply authorization
policy on all operations
– May be site-, service-, instance-, etc., specific
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OGSA defines standard interfaces for remote
management of access control policy
– OperationAuthorizationManagement
– SubjectEquivalency
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Notification Interfaces
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NotificationSource for client subscription
– One or more notification generators
> Generates notification message of a specific type
> Typed interest statements: E.g., Filters, topics, …
> Supports messaging services, 3rd party filter services, …
– Soft state subscription to a generator
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NotificationSink for asynchronous delivery of
notification messages
A wide variety of uses are possible
– E.g. Dynamic discovery/registry services, monitoring,
application error notification, …
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Use of Web Services (1)
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A Grid service interface is a WSDL portType
A Grid service definition is a WSDL extension
(serviceType) containing:
– A set of one or more portTypes supported by
the service
– portType & serviceType compatibility
statements, to support upgradability
> For discovery of compatible services when interfaces are
upgraded
– Implementation version information
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Use of Web Services (2)
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A GSR is a WSDL document with extensions:
– Extension to service element to reference
serviceType
– Service element extensions to carry the GSH,
and the expiration time of the GSR
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A GSH is an URL, with the following properties:
– Globally unique for all time
– http get on GSH + “.wsdl” returns GSR
– Can derive GSH to Mapper from it
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Registry returns WS-Inspection documents
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Using OGSA
to Construct Grid Environments
(a) Simple Hosting
Environment
Factory
Service
Service
Registry
Service
Factory
H2R
Mapper
Factory
...
Service
Registry
Service
...
...
Factory
(b) Virtual Hosting
Environment
Service
F
S
S
E2E
Factory
E2E Reg
H2R
Mapper
...
Service
R
M
F
(c) Compound Services
S
F
F
S
S
E2E H2R
Mapper
Service
E2E S
R
M
F
1
S
S
R
M
S
...
E2E S
S
R
M
F
2
S
E2E S
S
S
In each case, Registry handle is effectively the unique
name for the virtual organization.
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OGSA and the Globus Toolkit
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Technically, OGSA enables
– Refactoring of protocols (GRAM, MDS-2, etc.)—while
preserving all GT concepts/features!
– Integration with hosting environments: simplifying
components, distribution, etc.
– Greatly expanded standard service set
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Pragmatically, we are proceeding as follows
– Develop open source OGSA implementation
> Globus Toolkit 3.0; supports Globus Toolkit 2.0 APIs
– Partnerships for service development
– Also expect commercial value-adds
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Globus Toolkit Refactoring
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Grid Security Infrastructure (GSI)
– Used in Grid service network protocol bindings
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Meta Directory Service 2 (MDS-2)
– Native part of each Grid service:
> Discovery, Registry, RegistryManagement, Notification
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Grid Resource Allocation & Mngt (GRAM)
– Gatekeeper -> Factory for job mgr instances
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GridFTP
– Refactor control channel protocol
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Other services refactored to used Grid services
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Summary:
Evolution of Grid Technologies
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Initial exploration (1996-1999; Globus 1.0)
– Extensive appln experiments; core protocols
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Data Grids (1999-??; Globus 2.0+)
– Large-scale data management and analysis
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Open Grid Services Architecture (2001-??, Globus
3.0)
– Integration w/ Web services, hosting environments,
resource virtualization
– Databases, higher-level services
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Radically scalable systems (2003-??)
– Sensors, wireless, ubiquitous computing
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Summary
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The Grid problem: Resource sharing &
coordinated problem solving in dynamic,
multi-institutional virtual organizations
Grid architecture: Protocol, service definition
for interoperability & resource sharing
Globus Toolkit a source of protocol and API
definitions—and reference implementations
– And many projects applying Grid concepts (&
Globus technologies) to important problems
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Open Grid Services Architecture represents
(we hope!) next step in evolution
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For More Information
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The Globus Project™
– www.globus.org
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Grid architecture
– www.globus.org/research/pap
ers/anatomy.pdf
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Open Grid Services
Architecture (soon)
– www.globus.org/research/pap
ers/ogsa.pdf
– www.globus.org/research/pap
ers/gsspec.pdf
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