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Grid services vs. Web services. Dana Petcu , Georgiana Macariu, Marc Francu, Alexandru Carstea IeAT, Romania. Content. Grid ws. Web services Similarities What is different? Overview of the SCIEnce activities at Timisoara. Similarities. Special forms of distributed computing

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grid services vs web services

Grid services vs. Web services

Dana Petcu, Georgiana Macariu,

Marc Francu, Alexandru Carstea

IeAT, Romania

  • Grid ws. Web services
    • Similarities
    • What is different?
  • Overview of the SCIEnce activities at Timisoara
  • Special forms of distributed computing
  • Both typically deal with wide-area distributed computing
  • A Grid service is basically a Web service with some additions
    • E.g. to make it able to store state information persistently rather than transiently at the server beyond the lifetime of a single request
  • Grid services have different goals from pure Web services:
    • WS: conceived to share information, (eg:
    • GS: conceived to share computing power and resources like disk storage databases and software applications (eg: EGEE)

“Grid service = Grid computing + Web services”

  • Every Grid service “is a” Web services, but not every Web service “is a” Grid service
web service
Web service
  • A software system built to support communication between two processing elements that are interconnected through a network
  • The most important requirement: interoperability
  • Interaction client-service provider is carried out using XML based messages
  • Messages are exchanged using an underlying protocol such as HTTP or SMTP.
  • A web service offers an interface described by a document that can be processed by a machine in automatic fashion
  • Use SOAP standard or REST standard
    • REST standard imposes that a request must specify all the information needed by the server to service the request (no stateful information should be kept at server level)
    • For SOAP standard the interface is defined using WSDL
grid services extends web services by
Grid services extends Web services by:
  • stateful services,
  • service instantiation,
  • named service instances and a two-level naming scheme,
  • a base set of service capabilities, including discovery facilities,
  • lifetime management
  • An instance of a service is stateless if it cannot remember prior events.
  • An instance of service is stateful if it can remember about prior actions (-> vars. within service to maintain vals between accesses)
  • A WS is usually stateless, A GS is stateful
  • A WS can be stateful using ad hoc methods
  • Grid services are bringing uniformity and consistency in this topic
  • State in the Web service is generally regarded as a bad thing!
  • Stateless Web services storing state information? By separating the Web service from the state information!
  • State keep it in a separate entity called resource
  • Each resource has a unique key
  • Statefull interaction with a Web service: instruct the Web service to use a particular resource.

Web Service + Resource = WS-Resource

Web services - stateless vs. stateful : bank service analogy(from
  • WS: no different discrete units of state (instances) named in a consistent manner
  • GS:
    • namable state
    • GS specification defines:
      • Factories and
      • Lifetime management services
    • A factory implements an operation that creates a new service instance and returns its handle and its initial termination time.
named service instances
Named service instances
  • WS: named by URIs
  • GS:
    • named at a first level by a Grid Service Handle (GSH) - an URI, an abstract name that refers only an instance (no information like the location, implementation, or status of the service)
    • A GSH is resolved at a second level into a Grid Service Reference (GSR)
from www cs indiana edu ysimmhan l talks simmhan b534 2004 pdf

GSH = http://extreme/services/foo/my-service

GSR (URL) = http://ooty:8080/foo-service

My Grid Service

Invoke method on service


GSH = http://extreme/services/service-registry

GSR (URL) = http://rainier:20202/service-registry

GSH = http://extreme/services/handle-resolver

GSR (URL) = http://rainier:10101/handle-resolver

Service Group


Handle Resolver










Get GSR for registry GSH


Returns http://rainier:20202/handle-resolver




Get all Entries about services.

Returns Metadata Content and the GSH (http://extreme/services/foo/my-service)

Select your service and get GSR for GSH

http://extreme/services/foo/my-service. Returns http://ooty:8080/foo-service.


Handle Resolver URL = http://rainier:10101/handle-resolver

Your Service Handle = http://extreme/services/foo/my-service

OR locate from Registry GSH = http://extreme/services/service-registry

service discovery
Service discovery
  • WS: UDDI registry, allow introspection and discovery of static information such as service interfaces and associated policy
  • GS: need support for transient service instances that are created or destroyed dynamically!
  • GT4
    • uses an own index service which locate service based upon user criteria
    • service discovery is based on Service Data Elements (SDEs) = a structured collection of information associated with a Grid service that allows a user to choose a service that satisfies its needs, e.g. functionality speed, cost.
  • related to the issues of resource reclamation associated with services in the event of
    • failures (eg. loss of network connectivity)
    • or lack of interest by any relevant clients (eg. service no longer ref. by any active process)
  • WS: cycle controlled by the Web Server
    • dynamically allocated when a request arrives
    • deallocated when that request/session ends
  • GS:
    • set a time (in SDE) when a service will self-destruct unless kept alive by subsequent increases in its termination time
    • service instance need not to be explicitly destroyed
transient vs non transient service
Transient vs. non-transient service
  • A transient service instance is one that can be created and destroyed (eg. for specific clients)
  • An non-transient (persistent) instance of a service outlives its client
  • WS: usually non-transient
  • GS: can be
    • stateful transient:
      • an instance assigned to each client and only that client can access stored information;
      • information retained between accesses and pertains to the client;
      • instance usually destroyed when its purpose has been fulfilled
    • stateful non-transient:
      • several clients share one instance of the service,
      • Stored information is available to all clients.
current standards
Current standards
  • GT4 and WSRF.NET currently implements Web Services Resource Framework (WSRF) that specifies stateful WS that extends WSs
  • WSRF: a collection of specifications
      • WS-ResourceProperties
      • WS-ResourceLifetime
      • WS-ServiceGroup
      • WS-BaseFaults
      • [WS-Notification]
      • [WS-Addressing]
  • M.C. Brown, Build grid applications based on SOA. Concepts behind SOA and how to move grid applications to SOA model, DeveloperWorks -- IBM's resource for developers, 2005,
  • A. Grimshaw, Grid services extend Web services, SOAWebServices Journal 506, 2003,
  • D.Petcu, Between Web and Grid-based Mathematical Service, Procs. ICCGI, IEEE Computer Society Press, 2006,
  • K. Champion, Stateless and stateful WS in the Grid community, 2004,
  • P. Shread, Web Services a Good Start For Grid, But Not Enough, Grid Computing Planet, 2003,
  • B. Sotomayor, Globus Toolkit 4 Programmer's Tutorial,
  • H. Stockinger, Grid Computing: A Critical Discussion on Business Applicability, IEEE Distributed Systs Online,vol.7,no.6,2006,
  • WSRF,
science activities at timisoara

SCIEnce activities at Timisoara

  • Access to Grid and Web services
  • Service discovery
  • Facilitate the creation on Grid symbolic services
  • A tool for accessing services from a CAS


    • Automatic creation of Grid/Web clients
    • Generic for any CAS
  • Overviews papers:
    • Identify state of the art
  • Research: propose some improvements for CAS related to Grids
  • In the next talk…
  • Now only some test interface

API Exercise:

papers http science ieat ro science research publications
Papers (
  • D. Petcu, D. Tepeneu, M.Paprzycki, T.Ida, Symbolic Computations on Grids, chapter 6 in "Engineering the Grid: status and perspective", eds. Beniamino di Martino, Jack Dongarra, Adolfy Hoisie, Laurence Yang, and Hans Zima, American Scientific Publishers, 2006, pp. 91-107
  • D. Petcu, Improving Computer Algebra Systems by Using Grid Services, in 1st Austrian Grid Symposium, J. Volkert, T. Fahringer, D. Kranzlmuller, W. Schreiner (eds.), Austrian Computer Society, Band 210, 2006, 102-110
  • D.Petcu, C.Bonchis, C.Izbasa, Symbolic Computations based on Grid Services, Int. Journal of Computers, Communications and Control (RO), Vol. 1, no. 1, 2006, 44-50
  • D.Petcu, Between Web and Grid-based Mathematical Services, ICCGI, 1-3 August 2006, IEEE Computer Society Press, eds. P. Dini, C. Popoviciu, C. Dini, Gunter Van de Velde, E. Borcoci
  • D.Petcu, Mathematics on the net: state of the art and challenges, 8th French-Romanian Colloquim on Applied Mathematics, Chambery, France, August 28-31, 2006, invited talk