Web Service Resource Framework WSMO Presentation Jos de Bruijn Digital Enterprise Research Institute http :// / WS-Addressing:

Jos de Bruijn 2 Agenda WSRF WS-Addressing How WS-Resource works Implied Resource Pattern WS-Resource lifecycle WS-Resource vs. WS-Context WS-Resource for WSMO?

Jos de Bruijn 3 WSRF Mainly an IBM effort, together with the Globus Alliance and HP Standardization through Global Grid Forum and OASIS Enables discovery of, introspection on and interaction with stateful resources Is based on OGSI (Open Grid Services Infrastructure), using current developments in Web Services standards [remark: not including WS-CAF] WSRF distinguished between a stateless Service and stateful Resources, acted upon by that Service

Jos de Bruijn 4 Web Service Resource Framework A set of six standards, of which only three have been released: –WS-ResourceProperties: how a Web Service interface relates to a WS-Resource –WS-ResourceLifetime lifetime management of WS Resources –WS-Notification event subscription and notification Unreleased: –WS-RenewableReference retrieving updates of invalid endpoint references –WS-ServiceGroup heterogeneous collections of Web Services –WS-BaseFaults faults / error messages

Jos de Bruijn 5 WS-Addressing Defines XML elements to identify endpoints and secure end-to-end endpoint identification Independent of underlying transport mechanism C Within WSRF, the endpoint reference is a pointer to a web service, constrained to the context of a specific WS-Resource; the context is opaque to the requestor WS-Addressing states that ReferenceProperties elements must appear as SOAP header elements in messages sent to the service

Jos de Bruijn 6 Some slides copied from the presentation: Bringing Grid & Web Services Together dr. Daniel Sabbah

Jos de Bruijn 7 Interface Web Service The WS-Resource framework model Web Service WSDL Run-time environment

Jos de Bruijn 8 Interface Web Service message Invoking a Web Service address Endpoint Reference Run-time environment The WS-Resource framework model

Jos de Bruijn 9 What is a WS-Resource –Examples of WS-Resources: Physical entities (e.g.. processor, communication link, disk drive) or Logical construct (e.g.. agreement, running task, subscription) Real or virtual Static (long-lived, pre-existing) or Dynamic (created and destroyed as needed) Simple (one), or Compound (collection) –Unique (for the Web Service) - Has a distinguishable identity and lifetime –Stateful - Maintains a specific state that can be materialized using XML –May be accessed through one or more Web Services resource The WS-Resource framework model

Jos de Bruijn 10 id 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 The WS-Resource framework model

Jos de Bruijn 11 id context Interface Web Service message id message Using a Web service to access a WS-Resource id address resource Endpoint Reference The WS-Resource framework model Run-time environment

Jos de Bruijn 12 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 The WS-Resource framework model Run-time environment Endpoint Reference

Jos de Bruijn 13 Implied Resource Pattern Ensures data encapsulation Describes the way WS-Addressing is used to associate a stateful resource with the execution of message exchanges implemented by a web service. A WS-Addressing EndpointReference must include a ReferenceProperties element, which identifies the resource to be associated with the execution of all message exchange performed using this EndpointReference The stateful resource associated with a given message exchange is treated as implicit execution context for the message request The WS-Resource context is managed by the Web Service

Jos de Bruijn 14 WS-Resource lifecycle Actual creation and destruction and hidden from the requestor WS-Resources created by WS-Resource factories (cf. factory design pattern) WS-Resources are identified using a WS-Resource qualified endpoint reference WS-Resources can be destroyed explicitly by a call from the requestor or after a certain time- out

Jos de Bruijn 15 WS-Resource properties The state of a WS-Resource is expressed as an XML resource property document Requestor can query and modify state through WS message exchanges (e.g. using WS- MetaDataExchange) The resource property document is referred to in the WSDL document Provide can determine how much of the state of the resource to make visible

Jos de Bruijn 16 WS-Resource vs. WS-Context Very interesting thread on WS-Resource vs. WS-Context (part of WS-CAF): www-unix.gridforum.org/mail_archive/ogsi-wg/2004/01/threads.html#00014 WS-Resource seems to ignore WS-Context WS-Context provides a context independent of the service; WS- CTX relates messages with each other WS-Resource provides one endpoint reference (using WS- Addressing) for a resource, which is to be sent to the Web Service, when invoking WS-CTX is used for providing a context for message, without caring what this means; WS-Resource indicates how to retrieve a specific resource; in this sense they are orthogonal

Jos de Bruijn 17 WS-Resource for WSMO Message exchanges in WSMO are stateful It seems to make sense to use WS-Resource in the grounding in the choreography State of a conversation in WS-Resource? We should have a closer look at WS-Context