1. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 Resource wrappers, web services, grid services Jaspreet Singh School of Computer Science Cardiff University

2. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 Overview BDWorld Project Resource Wrappers BDWorld Datatypes BiodiversityWorld-GRID Interface (BGI) Communications Layer Web Services based BDW Wrappers Globus Toolkit 4.0 & WSRF Grid Services based BDW Wrappers Further Work

3. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 BDWorld Project A flexible and extensible problem solving environment (PSE) Brings together heterogeneous, globally distributed, biodiversity related resources and analytical tools The resources can be assembled into set of workflows to perform complex scientific analysis Provides consistent mechanisms across various facets to achieve interoperability The multi-layered architecture provides data related computation as part of a separate layer Provides uniform interfaces for heterogeneous resources Provides a common resource access mechanism Standard data flow mechanisms that use well defined data objects Uses Triana Workflow System for assembling and executing workflows

4. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 BDWorld Wrappers A mechanism to provide consistent interface to resource users and a standard resource access/invocation mechanism Insulate the core BDWorld System from heterogeneous resource Retains flexibility to use various operations supported by each resource Provides a generic access mechanism Wraps various kinds of resources and analytical tools Can be deployed in Web Services/Grid environment Provides interoperability mechanisms between client and heterogeneous resources Operations on remote resources is invoked via the invokeOperation() method implemented by all the wrappers Wrappers give consistent form to data retrieved from heterogeneous resources by encapsulating them into BDWorld data types

5. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 InvokeOperation() method The parameters of invokeOperation()method identify: theResourceHandle: name of the resource to be invoked theOperationHandle: name of the operation to be invoked on the remote resource/tool theDataCollection is input data collection for the remote resource

6. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 Triana Workflow System Wrapper Logic Data Transformation Configuration Tools Data Transformation Tools BDW Wrapper Standard Operations External Tools BGI Communications Layer BDW Wrapper Architecture Remote Resource Datatype Tools Abstract Wrapper

7. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 BDWorld Datatypes Encapsulate different types of data and sub-datatypes for transporting data between end points Datatypes can be transformed into xml representations which can be easily serialised Xml schema for datatypes conform to W3C standards Datatypes are flexible enough to encapsulate user defined xml documents or data in string representation They also act as parsing tool to extract data from raw xml Higher level datatypes can hold several sub datatypes and each sub datatype can hold several pieces of data They are extensible and support incorporation of new datatypes.

8. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 BDWorld Datatypes

9. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 BDWorld-GRID Interface (BGI) Layer Provides standard mechanisms for invoking operations on heterogeneous resources provides seamless access to BDW resources via resource wrappers Uses Xml/SOAP messaging system for invoking operations on resource wrappers Act as an integrated mechanism for accessing all resource wrappers Isolates resources/resource wrapper implementation to enable use of web services/grid technologies as part of a separate layer Isolates users from grid/web service complexities Helper Tool is provided to the user/triana for using the BGI layer Can provide multiple users/workflows with access to multiple resources at a time Interoperable with other e-Science projects

10. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 BDW Web Services Architecture Web services is a mechanism of enabling distribute computing based on open standards Wrappers are currently deployed in a web service environment which can be accessed via the BGI Layer at servers in Cardiff and Reading Web services enabled wrappers can be invoked via the BGI Helper Tool Axis SOAP engine provides the WSDL that exposes wrapper operations to outside world The MetadataAgent WS will provide access to MDR via the BGI Layer

11. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 Unit A Unit B Unit C Triana Workflow Units Data Parsing Tools BGI Communications Layer BGI Helper Tool Tomcat Servlet Container/ Axis Soap Engine MDR Metadata Agent WS BDW Web Services Architecture Remote Resource External Tool Java /non java resource WS Interface BDW Wrapper WS Interface BDW Wrapper WS Interface BDW Wrapper

12. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 Drawbacks of web services Web services are not stateful WS provide mechanisms for invoking remote operations but does not provide other services such as resource management, persistency, life cycle management, notification etc. Each web service needs to be deployed individually

13. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 GT4 Key Concepts Based on Open Grid Service Architecture (OGSA) OGSA defines common, standard and open architecture for grid-based applications Standardises various services common to grid applications (job management, resource monitoring and discovery, resource management, security services etc) Uses Web Services as underlying technology to enable distributed computing But Web Services are not stateful

14. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 Web Service Resource and Web Services Resource Framework (WSRF) WS-Resource construct expresses relationship between stateful resources and Web Services. It is pairing of web service with a resource WSRF is a set of web services specifications which define rendering WS- Resource approach in terms of specific message exchanges and related XML definitions It specifies how Web Services can be made stateful It defines conventions for managing state for applications to discover, inspect and interact with stateful resources in standard and interoperable way Using WSRF associations between a web service and one or more stateful resources can be established The state of the WS-Resource can be accessed through a web service interface by using endpoint references WSRF is the core of GT4

15. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 WSRF Specifications WS-ResourceProperties WS-ResourceLifetime WS-RenewableReferences WS-ServiceGroup WS-BaseFaults Related Specifications WS-Notification WS-Addressing

16. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 Applications OGSA Web Services WSRF Stateful Web Services Web Service extends OGSA WSRF requiresspecifies Relation between OGSA, WSRF and GT4 (source: [1])

17. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 WSRF – An approach to statefulness WSRF provides the mechanism to keep state information by keeping the Web Service and state information completely separate State information is stored in entity called resource A resource is be identified via its unique key When requiring stateful interaction, a web service can be instructed to use a particular resource The resources can be stored in memory or on secondary storage

18. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 ClientWeb Service A B C Resources Interaction of client with a stateful web service (source: [1]) Instruct client to use Resource A request response Web service loads resource A WS-Resource Client provides EPR corresponding to Resource A

19. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 Grid enabled BDW Resource Wrappers Java WS Core component of GT4 being used Prototype implementation of resource wrappers deployed in the grid environment Interaction of Grid enabled wrappers via the BGI Helper Tool Single integrated mechanism of invoking all resource wrappers in the grid environment Grid services invoked via the dynamic loading of resource wrappers Resource properties provide access to memory resident BDW cache data Access to cache data via EPR from Triana/client without invoking the resource behind again

20. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 Unit A Unit B Unit C Triana Workflow Units Data Parsing Tools BGI Communications Layer BGI Grid Helper Tool BgiWrapperService BgiWrapper BDWCache GT4 Container MDR Metadata Agent WS Remote Resource

21. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 Further Work Move computation on the grid in addition to resource access mechanism BDW Resource pool, automatic update of resources Making resources persistent BDW Heartbeat monitor Security, Index Service, Monitoring and Discovery System (MDS), OGSA-DAI for BDW resources

22. BiodiversityWorld GRID Workshop NeSC, Edinburgh – 30 June and 1 July 2005 References [1] Globus Tutorial http://gdp.globus.org/gt4-tutorial/http://gdp.globus.org/gt4-tutorial/ [2] Global Grid Forum http://www.ggf.org/ggf_abt_overview.htmhttp://www.ggf.org/ggf_abt_overview.htm [3]The WS-Resource Framework http://www.globus.org/wsrf/specs/ws-wsrf.pdf