Chapter 10: Execution Models Service-Oriented Computing: Semantics, Processes, Agents – Munindar P. Singh and Michael N. Huhns, Wiley, 2005

Chapter 102Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Highlights of this Chapter Interoperation Architecture Messaging Peer-to-Peer Computing Enterprise Service Bus CORBA Jini Grid Computing

Chapter 103Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Interoperation (Standards and Technologies) Requires surmounting a series of challenges Transport: HTTP, SMTP, SIP Messaging: XML (including XQuery …), SOAP Data and structure: WSDL Finding and binding: UDDI, QoS techniques Semantics: ontologies (RDF, OWL, IEEE SUO, Cyc) Transactions: WS-Coordination, WS-AtomicTransaction, WS-BusinessActivity Process: OWL-S, WS-CDL, PSL, BPEL4WS Policy: XACML Dynamism: FIPA AMS, RuleML, Jason Cooperation: FIPA ACL, multiagent systems

Chapter 104Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Application Interoperation

Chapter 105Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Architectural Elements Low-level (included in app server): Directories, messaging Data and process interoperation: Metadata and transformations Routing Rules engine Business process Modeling and execution engine

Chapter 106Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Invocation-Based Adapters Common in distributed object settings (EJBs, DCOM, CORBA) Synchronous: blocking method invocation Asynchronous: nonblocking (one-way) method invocation with callbacks Deferred synchronous: (in CORBA) sender proceeds independently of the receiver, but only up to a point Execution is best effort, at most once More than once is OK for idempotent operations, not otherwise

Chapter 107Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Message-Oriented Middleware: 1 Analogous to store and forward networks Queues: point to point Support posting and reading messages Topics: logical multicasts Support publishing and subscribing to application-specific topics Thus more flexible than queues Some messages correspond to event notifications

Chapter 108Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Message-Oriented Middleware: 2 Inherently asynchronous Supports loose coupling Reliability: cannot guarantee successful message delivery, but can provide failure notification Usually used through an invocation-based interface By polling or via registered callbacks onMessage() method of message-driven beans

Chapter 109Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Enterprise Service Bus An abstraction separating enterprise services and transport Supports services as units of functionality Supports routing of messages (via MoM or Web services or anything else) Enables an architectural style in which transformers convert message formats Often accompanied with modules for process, policy, logging, identity management, …

Chapter 1010Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Peer-to-Peer Computing Models of computation Symmetric client-server: Each party can query the other, thereby giving each power over the other at different times Doesn't fundamentally look beyond client-server Asynchrony: While the request-response paradigm corresponds to pull, asynchronous communication corresponds to push Undesirable: push applications that place their entire intelligence on the server (pushing) side Federation of equals: When the participants can enact whatever protocols they see fit

Chapter 1011Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Chapter 10 Summary Increasingly, interoperation architectures promote loose coupling and arms-length relationships Hence focus on messaging Similar challenges have been addressed multiple times but service improvements result in easier composition and deployment of services