Chapter 10 Execution Models ServiceOriented Computing Semantics Processes

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

Highlights of this Chapter n n n n Chapter 10 Interoperation Architecture Messaging Peer-to-Peer Computing Enterprise Service Bus CORBA Jini Grid Computing Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 2

Interoperation n (Standards and Technologies) Requires surmounting a series of challenges n n n n n Transport: HTTP, SMTP, SIP Messaging: XML (including XQuery …), SOAP Data and structure: WSDL Finding and binding: UDDI, Qo. S techniques Semantics: ontologies (RDF, OWL, IEEE SUO, Cyc) Transactions: WS-Coordination, WS-Atomic. Transaction, WS-Business. Activity Process: OWL-S, WS-CDL, PSL, BPEL 4 WS Policy: XACML Dynamism: FIPA AMS, Rule. ML, Jason Cooperation: FIPA ACL, multiagent systems Chapter 10 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 3

Application Interoperation Chapter 10 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 4

Architectural Elements n Low-level (included in app server): n n Data and process interoperation: n n Metadata and transformations Routing Rules engine Business process n Chapter 10 Directories, messaging Modeling and execution engine Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 5

Invocation-Based Adapters n Common in distributed object settings (EJBs, DCOM, CORBA) n n 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 n Chapter 10 Synchronous: blocking method invocation Asynchronous: nonblocking (one-way) method More than once is OK for idempotent operations, not otherwise Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 6

Message-Oriented Middleware: 1 Analogous to store and forward networks n Queues: point to point n n Topics: logical multicasts n n n Chapter 10 Support posting and reading messages Support publishing and subscribing to application-specific topics Thus more flexible than queues Some messages correspond to event notifications Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 7

Message-Oriented Middleware: 2 n n Inherently, asynchronous Supports loose coupling Reliability: cannot guarantee successful message delivery, but can provide failure notification Usually used through an invocation-based interface n n Chapter 10 By polling or via registered callbacks on. Message() method of message-driven beans Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 8

Enterprise Service Bus An abstraction separating enterprise services and transport n Supports services as units of functionality n Supports routing of messages (via Mo. M or Web services or anything else) n Enables an architectural style in which transformers convert message formats n Often accompanied with modules for process, policy, logging, identity management, … Chapter 10 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 9

Peer-to-Peer Computing Models of computation n Symmetric client-server: Each party can query the other, thereby giving each power over the other at different times n n Asynchrony: While the request-response paradigm corresponds to pull, asynchronous communication corresponds to push n n Chapter 10 Doesn't fundamentally look beyond client-server 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 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 10

Chapter 10 Summary n n n Chapter 10 Increasingly, interoperation architectures promote loose coupling and arms-length relationships Hence focus on messaging Facilitate composition and deployment of services Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns 11