soa principles : 4.service loose coupling
TRANSCRIPT
Principles OF
SOA From knowledge To practice
SUBMITTED BY : MOHAMED ZAKARYA
AGENDA
Service orientation principles
Standardized Service Contract Service Reusability Service Discoverability Service Composability Service Loose Coupling Service Abstraction Service Autonomy Service Statelessness Thanks
PART 1
INTRODUCTION
SERVICE ORIENTATION PRINCIPLES
Standardized Service
Contract
ServiceReusability
ServiceComposability
ServiceAutonomy
Service Loose
Coupling
Service Statelessness
ServiceAbstraction
ServiceDiscoverability
SERVICE ORIENTATION PRINCIPLES
Service ReusabilityService contain agnostic logic that can be position as reusable enterprise resource.
Standardized Service ContractService in same inventory are in compliance of same design service contract standards.
Service CompositionServices are effective composition participants.
Service DiscoverabilityService meta data available for discoverability and interpreted.
Service Loose CouplingContract decoupled from surrounding environment.
Service AutonomyServices exercise a high level of control over their underlying runtime execution environment.
Service StatelessnessServices minimize resource consumption , reduce state information.
Service AbstractionContract contains only essential information , that is published to consumers.
PART 1
SERVICE
LOOSE COUPLING
INTRODUCTION
Service Loose CouplingContract decoupled from surrounding environment.
Anything that connects has coupling
Levels of coupling from loose to tightly coupled
Loose coupling is advocated between a service contract and its consumers a service contract and its underlying implementation
A measure of coupling between two things is equivalent to level of dependency that exists between them
LOOSE COUPLING PURPOSE
Position the service as a continually useful and accessible resource
Protecting Service and its consumers from forming any relationships that may constrain or inhibit them in the future
ABOUT THE PRINCIPLE
TitleServices are loosely coupled
DescriptionService contracts impose low consumer coupling requirements and are themselves decoupled from their surrounding environment.
Goals
Minimize dependency impact
Environment in which services and their consumers can be adaptively
evolved over time with minimal impact on each other
Implementation requirementsRequire more runtime processing , consume more runtime resources especially on concurrent access and high usage scenarios
SERVICE CONTRACT COUPLING TYPES
SERVICE CONTRACT COUPLING TYPES
Logic-to-Contract Coupling
Contract-to-Logic Coupling
Contract-to-Technology Coupling
Contract-to-Implementation Coupling
Contract-to-Functional Coupling
1. LOGIC-TO-CONTRACT COUPLING
A recommended approach to building a service is to design its physical contract prior toits underlying solution logic. [positive type of coupling]
Tune the underlying logic in support of the service contract
This [contract first] process
2. CONTRACT-TO-LOGIC COUPLING
Many contracts for Web services in particular have been derived from existing solution logic
service contract is hardwired to the characteristics of its implementation environment.
that shortens lifespan of service contract and inhibits long-term evolution of the service
Examples of this coupling :
Auto-generation of WSDL definitions usingcomponent interfaces
Auto-generation of XML schemas from database tables and other parts of physical data models
3. CONTRACT-TO-TECHNOLOGY COUPLING
Impose technology-specific characteristics on the contract as proprietary as the developmenttechnology used to build the service itself.
limits the potential consumers to those who are capable of supporting the technology.
service contract is not required to express proprietary details of the underlying solution logic
Avoid this coupling type : gives service owner ability to swap service implementation technologies without affecting service’s existing consumer base.
Examples of this coupling :
Limit interaction with serviceusing NET Remoting only(overtime become deprecated)
4. CONTRACT-TO-IMPLEMENTATION COUPLING
physically deployed service will be comprised of or will require access to a collection of implementation technologies and products beyond the core service logic.
Example :
Auto-generation of schema from database tables or views will end up placing physical data model details into the service contract.
5. CONTRACT-TO-FUNCTIONAL COUPLING
Logic encapsulated by a service is specifically designed in support of a body of functionality that exists outside of the service boundary
Result in : Corresponding service contract can become functionally coupled, resulting in contract-to-functional coupling
Examples Parent Process Coupling
SERVICE CONSUMER COUPLING TYPES
Consumer-to-Implementation Coupling
Consumer-to-Contract Coupling
1. CONSUMER-TO-IMPLEMENTATION COUPLING
A service consumer is technically not forced to access a service via its contract
There are often other entry points that may seem more attractivefor reasons such as improved performance and design simplicity
inhibit both service and consumer in the future.
2. CONSUMER-TO-CONTRACT COUPLING
any time a consumer bindsto its contract,
This is a recommended and desirable form of coupling because it achieves the greatestamount of independence between the consumer and the service.
2. CONSUMER-TO-CONTRACT COUPLING
When the service contract is technology coupled, its service consumers will be forced to become coupled
to the service’s underlying technology.
2. CONSUMER-TO-CONTRACT COUPLING
When the service contract is functionally coupled, its service consumers are required to couple to the service’s
underlying functional dependencies
2. CONSUMER-TO-CONTRACT COUPLING
When the service contract is derived from parts of the service’s implementation resources, its consumers will also
become coupled to those parts of the implementation environment. This is especially undesirable when the
resources do not belong exclusively to the service but are instead shared parts of the overall architecture
SERVICE CONTRACT COUPLING TYPES
REFERENCES
http://www.soaschool.com/
http://serviceorientation.com/index.php/soaglossary/index
http://soapatterns.org/
http://www.servicetechmag.com/
http://www.soaschool.com/certifications
http://www.servicetechbooks.com/
ANY QUESTIONS
