A Survey on Service Composition Languages and Models Antonio Bucchiarone Antonio Bucchiarone and Stefania Gnesi Istituto di Scienza e Tecnologie dell’Informazione ”A. Faedo” (ISTI - CNR) Area della Ricerca CNR di Pisa, Pisa, Italy

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Agenda Introduction Current Models  Web Services and Semantic Web Services  Static and Dynamic Composition A comparison of Current Languages  Service Composition Requirements  High-level key features of BPEL4WS, BPML, WSCI, WS-CDL and DAML-S Conclusions and Future Work

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Introduction Composition of Services (B2B and EAI) Business world  XML-based standards to formalize the specification of WS  Composition of WSs  Execution of WSs Semantic Web Community  Web resources (RDF), description and relationships  Preconditions and effects described by terms precisely defined in ontologies Models of Services Composition  Static and Dynamic Languages  BPEL4WS, BPML, WSCI, WS-CDL, DAML-S Comparison by considering some specific requirements

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 The environment Service Oriented Computing (SOC)  autonomous and heterogeneous computational entities, that run on different platforms are owned by different organizations are described, published and discovered are combined using an engine that coordinates the interaction among collaborative services Web Services and Semantic Web Services

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Web Services these WS standards do not deal with the dynamic composition of existing services total absence of semantic representation for services available on the internet.

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Semantic Web Services Extension of the current web technologies  Information with a well-defined meaning  Markup language with a well-defined semantics  Fully automation of all the stages in the WS lifecycle  WWW as a globally linked database where web pages are marked with semantic annotations  Ontologies to formalize domain concepts that are shared among services DAML-S

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Static Composition It specifies the order in which services are invoked the conditions under which a certain service may not to be invoked combines available services adding a central coordinator (orchestrator) responsible for invoking and combining the single sub-activities. it defines complex tasks via the definition of the conversation that should be undertaken by each participant. BPEL4WS WS-CDL BPML WSCI

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Dynamic Composition static composition: flow of information and the binding between services are known a priori compose service dynamically semantic web technology : RDF + Ontologies DAML-S

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Some Requirements We compare BPEL4WS, BPML, WSCI, WS-CDL and DAML-S according to the following requirements: Modeling collaborations Modeling the control of execution Representation of Roles Transactions and Compensations Exception handling Semantic Support Business agreement support Software vendor support

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Collaboration and Execution The ability to perform long-lived, p2p collaboration between participating services. Collaboration should be modeled in terms of interactions (i.e., message exchanges). The ability of assembling and incorporating individual WSs into the course of a business process execution

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Representation of Role Parties involved in business processes play different roles in different process stages. Behavior assumed by parties in different scenarios.

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Transactions and Compensations The ability of managing transactions and compensations over service invocations Compensations are needed to rollback the effects of completed transactions when there is a failure.

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Exceptions handling The composition of WSs uses external WSs that are purely under the control of the WSs owner. Process invocation should handle exceptions when the invoked WSs do not respond.

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Semantic support Representation of the semantics of composed services to facilitate the automated composition of WSs Description of the semantics to enable dynamic service discovery and invocation.

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Business agreement support Business agreement defines the contract between involved parties. It is necessary to represent QoS in composed WSs.

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Software vendor support Whether the language has software support.

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 BPEL4WS key features Partner links to model p2p collaboration “myRole” and “PartnerRole”: the only means for giving a name to the roles Transactions are realized through fault and compensation handlers A Fault Handler is used to catch an error. No semantic No business agreement support Many tools available  IBM WebSphere, Oracle BPEL Process Manager, Microsoft BizTalk, etc..)

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 BPML key features basic activities for sending, receiving, and invoking services It handles conditional, sequential, and parallel activities No Role representation! Support for persistence in long-running processes Robust exception handling mechanisms No automation support! Services and partners are specified at design time No support for business agreement Few tools available

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 WSCI key features Defines overall choreography of WS taking part in an interaction It does not focus on the definition of executable business processes Based on messages Role of Composition Partners Support for business transactions and exceptions Exceptional behaviour  Alternative patterns of behaviour No support for Semantic description or Business agreement. Few tools

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 WS-CDL key features Global view of the observable behavior of a set of Web Services p2p collaboration between participants using Choreography No support for execution Roles, Participants and Relationships Finalizer Block is used for handling transactions and compensations Exception Blocks catch faults No support for Semantic description or Business agreement. No tools.

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 DAML-S key features A DARPA Agent Markup Language for Services Web Service Discovery & Selection  Find an airline offerings flights to Rome Web Service Invocation  Book flight tickets on Alitalia to arrive 13th June Web Service Composition & Interoperation  Arrange taxis, flights and hotel to travel from Rome to Palermo Monitoring Web Service Execution  Has the taxi to Palermo Airport been reserved? Tools availability (Academy and Industry)  DAML+OIL reasoners  DAML-S editors

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 DAML-S Upper Ontology. input types. output types. preconditions. postconditions. communication protocol (RPC, HTTP, …). port number. marshalling/serialization process flow composition hierarchy process definitions

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Summary

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Conclusion Initial results and much more details must be described An overview of major Web and Semantic Web Services composition languages BPEL4WS, WSCI, WS-CDL and BPML focus on service syntax Definition of a new process that interact with existing one must be done manually  hard, time consuming and error prone task DAML-S: description of the semantics of services Automation of WSs tasks  Discovery and composition

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Future Work We wish to extend the comparison with more details  Tool support, messaging models supported, examples, etc..  QoS characteristics that each language is able to describe in order to define a QoS Service Composition. Correctness Verification of service composition  BPEL4WS  automata or Petri Nets  DAML-S  Petri Nets or Prolog  ….. A Survey on Service Composition Approaches: From Industrial Standards to Formal Methods (submitted to WS-FM06 workshop). Automata, Petri Nets, Process Algebras

Antonio Bucchiarone WsMaTe ’06 - Palermo, 9 June 2006 Thank you for your attention Good lunch!! 