CSC/ECE 517 Fall 2009/wiki2 16 rs: Difference between revisions
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[[Image:protocolbridging.png]] Problem: Services using different communication protocols or different versions of the same protocol cannot exchange data. | [[Image:protocolbridging.png]] | ||
Problem: Services using different communication protocols or different versions of the same protocol cannot exchange data. | |||
Solution: Bridging logic is introduced to enable communication between different communication protocols by dynamically converting one protocol to another at runtime. | Solution: Bridging logic is introduced to enable communication between different communication protocols by dynamically converting one protocol to another at runtime. | ||
Revision as of 04:46, 9 October 2009
CSC/ECE 517 Fall 2009/wiki2 16 rs
SOA provides another view of providing functionality based upon services offered in terms of protocols and a specific API. Research and report on what patterns have been proposed and are utilized within this domain. How do they differ from traditional design patterns proposed by Eric Gamma, Richard Helm, Ralph Johnson, and John Vlissides? How are they similar?
Introduction
SOA provides another view of providing functionality based upon services offered in terms of protocols and a specific API. Research and report on what patterns have been proposed and are utilized within this domain. How do they differ from traditional design patterns proposed by Eric Gamma, Richard Helm, Ralph Johnson, and John Vlissides? How are they similar?
This page reviews the different service oriented architecture patterns proposed for protocols and compares them them with the corresponding patterns which were proposed for object oriented reuse.
Service Oriented Architecture-An Overview
SOA-Definition
A service-oriented architecture is essentially a collection of services. These services communicate with each other.The communication can involve either simple data passing or it could involve two or more services coordinating some activity. Some means of connecting services to each other is needed.Rather than defining an API, SOA defines the interface in terms of protocols and functionality. An endpoint is the entry point to such an SOA implementation.Service-orientation requires loose coupling of services with operating systems, and other technologies that underlie applications. SOA separates functions into distinct units, or services, which developers make accessible over a network in order to allow users to combine and reuse them in the production of applications. These services communicate with each other by passing data from one service to another, or by coordinating an activity between two or more services.
Why SOA?
Vast majority of Businesses working in the field of Information Technology have to justify their projects with a return on their investments. This puts Information Technology, as a field under enormous pressure. Information Technology must boast requirements that are increasingly responsive and flexible to the shifting needs of different Businesses.
Firms dealing with Information Technology must also be able to face the challenge of taking on an array of software systems that may or may not be compatible with one another. Moreover, Information Technology has to face demands to bring new commercial services to a much wider array of customers. Customers may access services through web interfaces, or may be part of a supply chain that needs to decrease the time and cost of manufacturing.
Thus, Information Technology companies are always on the look out for solutions that will help them meet the above demands – without having to spend a lot of money.SOA offers a solution to satisfy the above needs of the industry
SOA-Benifits
In architectural terms, a modern architectural design should be Service Oriented, loosely coupled, driven by events, able to support both integration and assembly, aligned with valuable life cycle support processes, and able to leverage existing infrastructure and applications.
When it comes to Service Oriented Architecture, it tends to offer a variety of different advantages over more traditional methods of distributing computing. These include offering business services across several platforms; providing location independence; providing authentication as well as authorization support on ever tier; a loosely coupled approach; and dynamic search and connectivity to other services. At the same time, it allows that services do not have to be located on a particular system or network.
Design Patterns in SOA
A design pattern is a general reusable solution to a commonly occurring problem in software design. A design pattern is not a finished design that can be transformed directly into code. It is a description or template for how to solve a problem that can be used in many different situations.Design patterns typically show relationships and interactions between classes or objects, without specifying the final application classes or objects that are involved.
Design Patterns proposed
The proposed Design Patterns for SOA fall in to following categories.They are listed below and corresponding patterns in each category are given.
Foundational Inventory Patterns
examples for this category are Enterprise Inventory,Domain Inventory,Service Normalization,Logic Centralization, Service Layers Canonical Protocol,Canonical Schema
Logical Inventory Layer Patterns
examples for this category are Utility Abstraction,Entity Abstraction,Process Abstraction
Inventory Centralization Patterns
examples for this category are Process Centralization,Schema Centralization,Policy Centralization,Rules Centralization.
Inventory Implementation Patterns
examples for this category are Dual Protocols,Canonical Resources,State Repository,Stateful Services,Service Grid,Inventory Endpoint,Cross-Domain Utility Layer
examples for this category are Canonical Expression,Metadata Centralization,Canonical Versioning
examples for this category are Functional Decomposition,Service Encapsulation,Agnostic Context,Non-Agnostic Context,Agnostic Capability
Service Implementation Patterns
examples for this category are Service Facade,Redundant Implementation,Service Data Replication,Partial State Deferral,Partial Validation,UI Mediator
examples for this category are Exception Shielding,Message Screening,Trusted Subsystem ,Service Perimeter Guard
Service Contract Design Patterns
examples for this category are Decoupled Contract,Contract Centralization,Contract Denormalization,Concurrent Contracts,Validation Abstraction
examples for this category are Legacy Wrapper, Multi-Channel Endpoint,File Gateway
examples for this category are Compatible Change,Version Identification,Termination Notification,Service Refactoring,Service Decomposition,Proxy Capability,Decomposed Capability,Distributed Capability
Capability Composition Patterns
examples for this category are Capability Composition,Capability Recomposition
examples in this category are Service Messaging,Messaging Metadata,Service Agent,Intermediate Routing,State Messaging,Service Callback,Service Instance Routing,Asynchronous Queuing,Reliable Messaging,Event-Driven Messaging.
Composition Implementation Patterns
examples for this category are Agnostic SubController,Composition Autonomy,Atomic Service Transaction,Compensating ServiceTransaction
Service Interaction Security Patterns
examples for this category are Data Confidentiality, Data Origin Authentication, Direct Authentication, Brokered Authentication
examples for this category are Data Model Transformation,Data Format Transformation, Protocol Bridging
Common Compound Design Patterns
examples for this category are Orchestration,Enterprise Service Bus,Service Broker,Canonical Schema Bus,Official Endpoint,Federated Endpoint Layer,Three-Layer Inventory
Example Design Patterns
Canonical protocol
Dual protocol
Protocol Bridging
Problem: Services using different communication protocols or different versions of the same protocol cannot exchange data.
Solution: Bridging logic is introduced to enable communication between different communication protocols by dynamically converting one protocol to another at runtime.
From the above figure it can be noticed that the consumer programs interact with a middle-tier broker that provides protocol bridging features. Separate protocol adapters are used to translate the two incompatible protocols to the required SOAP version 1.2 over HTTP. The broker then transmits the messages to the service on behalf of the consumers.
UI Mediator
Service Facade
