WS-Resource Framework University of Amsterdam

Grid and Web Services: Convergence? Grid Web However, despite enthusiasm for OGSI, adoption within Web community turned out to be problematic Started far apart in apps & tech OGSI GT2 GT1 HTTP WSDL, WS-* WSDL 2, WSDM Have been converging ? “WS-Resource Framework: Globus Alliance Perspectives” I. Foster

Grid and Web Services: Convergence: Yes! Grid Web The definition of WSRF means that Grid and Web communities can move forward on a common base WSRF Started far apart in apps & tech OGSI GT2 GT1 HTTP WSDL, WS-* WSDL 2, WSDM Have been converging “WS-Resource Framework: Globus Alliance Perspectives” I. Foster

Web Service and State Web service interfaces frequently provide a user with the ability to access and manipulate state –Message exchanges that Web services implement are frequently intended to enable access to stateful resources. However, the notion of stateful resources acted upon by the Web service implementation is not explicit in the interface definition. Modeling Stateful Resources with Web Services

Possible association between State and Services A stateless service implements –message exchanges with no access or use of information not contained in the input message A conversational service implements –a series of operations such that the result of one operation depends on a prior operation and/or prepares for a subsequent operation A service that acts upon stateful resources –access to, or manipulates a set of logical stateful resources based on messages it sends and receives.

Stateless Implementations, Stateful Interfaces A Service that acts upon stateful resources may be described “stateless” –if it delegates responsibility for the management of the state to another component. The service is responsible for the state of the resource between message exchanges

Web Service and State It is desirable to define Web service conventions to enable: – the discovery of, introspection on, and interaction with stateful resources in standard and interoperable ways. WS-Resource is approach to modeling state in a Web services context WS-Service Group WS-Renewable References WS-Notification Modeling Stateful Resources with Web Services WS-Base Faults WS-Resource Properties WS-Resource Lifetime

Run-time environment Web Service and State A WS-Resource is defined as the composition of a Web service and a S-Resource –Expressed as an association of an XML document with defined type with a Web services portType –Addressed and accessed according to the conventional use of WS-Addressing endpoint references context resource S-Resource identifier is encapsulated in an endpoint reference to identify the S-Resource to be used in the execution of a Web service message exchange. Interface Web Service Dr. Daniel Sabbah “Bringing Grid & Web Services Together”, IBM Software Group

Interface Web Service message Invoking a Web Service address Endpoint Reference Run-time environment WS-Addressing Dr. Daniel Sabbah “Bringing Grid & Web Services Together”, IBM Software Group

WSRF & WS-Addressing WS-Addressing standardizes –The endpoint reference used to represent the address of a WS. –endpoint contain metadata associated with the WS service description information reference properties

WS-Resource and WS-Addressing SW (2) represents an explicit WS-Resource factory –SW (2) returns an Endpoint reference to the requestor. –“C” is S-resource created The endpoint reference (3) contains –Wsa:Address (4) refers to the network transport-specific address of the WS (URL). same address that would appear within a port element in a WSDL of the WS –wsa:ReferencePropertie contain an XML serialization of a S-Resource identifier.

WS-Resource-qualified endpoint reference the endpoint reference represents a pointer to the WS-Resource service requestor –must understand that the endpoint reference refers to a WS-Resource. –must recognize that the endpoint reference is a WS-Resource qualified endpoint reference.

WS-Resource Relationship Cardinality A WS can execute message exchanges against: – zero –more S-Resources defined as instances of the resource property document. A single WS at a particular endpoint is associated with several individual S-Resources

OGSA Services can be defined and implemented as Web services OSGA can take advantage of other Web services standards OGSA can be implemented using standard Web services development tools Grid applications will NOT require special Web services infrastructure Network OGSA Enabled Storage OGSA Enabled Servers OGSA Enabled Messaging OGSA Enabled Directory OGSA Enabled File Systems OGSA Enabled Database OGSA Enabled Workflow OGSA Enabled Security OGSA Enabled Web Services WS-Resource Framework is an evolution of OGSI OGSI – Open Grid Services Infrastructure How WSRF is related to OGSA? Web Services OGSA Architected Services Applications WS-Service Group WS-Renewable References WS-Notification Modeling Stateful Resources with Web Services WS-Base Faults WS-Resource Properties WS-Resource Lifetime Dr. Daniel Sabbah “Bringing Grid & Web Services Together”, IBM Software Group

WS-Resource Framework WS-Resource framework allows WS-Resources to be –declared, created, accessed, monitored for change, and destroyed via conventional Web services mechanisms, but –does not require that the WS component of the WS-Resource to be implemented as a stateful message processor.

Interface Web Service message Creating / Locating a WS-Resource address Endpoint Reference resource Endpoint Reference Web Service either locates or creates a WS-Resource addres s id WS-Resource framework model Run-time environment Dr. Daniel Sabbah “Bringing Grid & Web Services Together”, IBM Software Group

contex t Interface Web Service message id message Using a Web service to access a WS-Resource id address resource Run-time environment Endpoint Reference WS-Resource Framework Dr. Daniel Sabbah “Bringing Grid & Web Services Together”, IBM Software Group

context Interface Web Service message id message Using a Web service to access a WS-Resource id address resource Endpoint Reference WS-Resource Framework Run-time environment Dr. Daniel Sabbah “Bringing Grid & Web Services Together”, IBM Software Group

WS-Resource Framework WS-Resource framework, is a set of five technical specifications define in terms of –specific WS message exchanges –and related XML definitions. The specifications allow –WS-Resource to be destroyed, –Type definition of a WS-Resource can be composed from the interface of a WS endpoint reference –Heterogeneous by-reference collections of Web services can be defined –Fault reporting can be made more standardized through use of an XML Schema

The five specification composing the WSRF

Service Composition Transports Messaging Description Quality of Experience (QoX) HTTP/HTTPS SMTP RMI / IIOP XSD WSDL SOAP XMLWS-Addressing WS-Renewable References WS-Metadata ExchangeWS-Policy WS-Service Group WS-Resource Properties JMS WS-Security WS-Reliable MessagingWS-Transaction WS-Resource Lifetime WS-Base Faults WS-Notification BPEL4WS How WSRF relates to other Web services standards? Dr. Daniel Sabbah “Bringing Grid & Web Services Together”, IBM Software Group

WS-ResourceLifetime Three main focus: –Creation of WS-Resource WS-Resource Factory –Assign identity to the WS- Resource –WS-Resource destruction Run-time environment context resource Interface Web Service Endpoint Reference ID

WS-Resource Lifecycle The lifetime of a WS-Resource is defined as the period between its creation and its destruction. WS-Resource creation using a WS-Resource factory(3) Assignment & use of the S- Resource identifier (2) destruction of a WS- Resource.

WS-Resource Creation WS-Resource factory is any WS capable of creating a WS- Resource –creating a new S-Resource –assigning the new S-Resource an identity, –associating the new S-Resource and its WS. The response message of a WS- Resource factory operation contains –WS-Resource-qualified endpoint reference containing a S- Resource identifier that refers to the new S-Resource

WS-Resource Destruction A requestor that wishes to terminate a WS- Resource uses WS-Resource-qualified endpoint reference to: – Immediate Destruction: send a destroy request message to the WS using by the endpoint reference. –Scheduled Destruction: message exchanges for establishing and renewing scheduled destruction times on WS-Resources

WS-Resource Properties –Resource state and metadata “Projected” as an XML document –GetResourceProperty operations allows client to query the state of the WS-Resource –SetResourceProperty operation allows client to modify the state of the WS- Resource – supports Insert, Delete and Update. resource 5A34C1DE03 Power

WS-Resource Properties Requestors determine a WS-Resource’s type by retrieving the WSDL portType definition. Requestors use Resource property to refer to –individual component of a WS-Resource’s state –XML document describing the type of a S- Resource within the WS-Resource is a WS-Resource properties document Requestors use WS message exchanges to read, modify, and query the XML document representing the WS-Resource’s state.

WS-Resource Properties WS-Resource properties document acts as a view on, the actual state of the WS-Resource. –the structure upon which requestor-initiated queries and updates can be directed. –Any operation that manipulates a resource property via the WS-Resource properties document must be reflected in the actual implementation of the WS-Resource’s state.

Renewable References The WS-RenewableReferences work defines mechanisms that can be used to renew an endpoint reference that has become invalid. For endpoint reference that refers to a WS- Resource, WS-RenewableReferences provides –a persistent and stable reference to the WS- Resource that can allow the same state to be accessed repeatedly over time.

Renewable References A WS-Addressing endpoint reference may contain –not only addressing –policy information concerning interactions with the service. –endpoint references are constructed by an authoritative source of the addressing and policy information. An endpoint reference made available to a client represents a copy of that information –When it becomes incoherent due to changes introduced by the authoritative source that effects the endpoint location and/or the policy

Service Groups The WS-ServiceGroup specification defines a means of representing and managing heterogeneous by- reference collections of Web services. –organize collections of WS-Resources, for example to build registries –build services that can perform collective operations on a collection of WS-Resources.

Service Groups The ServiceGroup specification express ServiceGroup: –membership rules, –Membership constraints –classifications. Groups can be defined. –as a collection of members that meet the constraints of the group as expressed through resource properties WS-ServiceGroup Client Destroy ServiceGroupEntry WS-ServiceGroup ServiceGroupEntry WS-Resource Add

Base Faults The WS-BaseFaults specification defines a base fault type for use when returning faults in a Web services message exchange. Used by all of the other WS-Resource framework specifications to bring consistency to the faults returned by the operations including – consistent reporting of faults relating to WS- Resource definition and use.

WS-Notification WS-Notification, defines a general, topic based WS system for (pub/sub) interactions that builds on the WS- Resource framework. –From the perspective of WS-Notification WS-Resource framework provides useful building blocks for representing and structuring notifications. –From the perspective of the WSRF, WS-Notification specifications extends WS-Resources by allowing requestors to ask to be asynchronously notified of changes to resource property value Broker Subscriber Publisher subscribe SS S notify

Evaluate how much did you get from this course 1.Possible association between State and Services? 2.Stateless Implementations, Stateful Interfaces? 3.what is WS-Resource? What is of composition WS-Resource 4.what is EPR? What is the composition of the EPR? 5.what is the role of the encapsulation? 6.what is the difference between EPR and Q-EPR? 7.WS-Resource Relationship Cardinality? Zero to many association between WS and S-Resource why do we need such a relationship? 8.WS-Resource Framework? 9.How many ways exist for the WS-Resource Destruction? Why do we need more than 10.why do we need the Renewable References specifications?