S6 SOA Service Layers 030409 CH9

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Service Layers

605.702 Service Oriented ArchitectureJohns-Hopkins University

Montgomery County Center, Spring 2009

Session 6, Lecture 6: March 4, 2009

Instructor: T. Pole



Agenda

• Required Reading for This Week• Chapter 9: Service Layers

• Today’s Presentation

– Update on Chapter 8

– Today’s Lecture

• Text CH 9

– Class Assignments

• Exercise #4, Implementing a Service Composition – Review for Mid Term Exam

• Mid Term is next week Wednesday March 11, 2009



Ch 8 Principles of ServiceOrientation

• Additional notes on Chapter 8 have beenadded to the lecture notes for last week,Lecture 5 2/25/09

• Check these notes in reviewing for the midterm exam next week



Chapter 9: Service Layers

• 9.1 SO and Contemporary SOA – Review table 9.1: how SOA characteristics are influenced by

Web Service specs and SO principles

• 9.2 Service Layer Abstraction – The service layer is between the application layer and the

business process layer (see Ch 8) – The implementation of the service interface layer is sub-divided

into layers following one of several different models

• 9.3 Application Service Layer• 9.4 Business Service Layer

• 9.5 Orchestration Service Layer• 9.6 Agnostic Services• 9.7 Service Layer Scenarios



9.2 Service Layer Abstraction

• Figure 9.2 shows the SOA layers WITHIN thesingle Service Interface Layer of the EnterpriseArchitecture – Business Process Layer

Processes of the Enterprise, not just the IT systems – Service Interface Layer

• Orchestration Layer

• Business Service Layer – NOT the Business Process Layer

• Application Service Layer – NOT the Application Layer

– Application LayerLegacy and Service Implementations



9.3 Application Service Layer

• Sits within the Service Interface Layer, andintegrates with the Application Layer below

• Solution (Meaning business process) agnostic,

are more generic and usually reusable acrossmultiple biz processes

• Can also be used to integrate other applicationservices

• Mixture of custom and COTS products• Hybrids may cross the line between business

and application logic



9.4 Business Service Layer

• Business services can be mapped to smallgrained or low level specific businessprocesses and entities

• Business oriented services can be – Entity Centric

– Task Centric

– Not both, but a business service layer can bea mix of both. Usually will be primarily one orthe other



9.5 Control or OrchestrationService Layer

• Introduces another type or service, theprocess service (aka but not synonymouswith the controller service)

• Directly relates to a business process• Controls other business, hybrid and

application/utility services to automate a

process• Can be implemented in “non-technical”

languages, e.g. BPEL



9.6 Agnostic Services

• Agnostic in this context can mean notbound to any one process

– e.g. an entity based service can be used by

multiple biz processes that involve that entity

– e.g. a utility service is by definition a genericreusable service not bound to any business

entity: task or entity based• Exist with the application service layer or

the business layer



9.7 Service Layer Scenarios

• There is no one layered model for the Service InterfaceLayer, some options are: – Single hybrid layer

• Common, doesn’t evolve well, brittle

– Hybrid over utility

• Also common among mature software developers, reuse driven – Biz task centric over utility

• Often the goal for mature business centric developers

– Task centric over entity centric over utility• Common among mature systems, flexible, adaptable

– Orchestration over hybrid over utility• Better then single hybrid, but extending to new orch. difficult

– Orchestration over task centric over utility• Flexible, evolves well, flexibly adjusts to change



Exercise #4: Implementing aService Composition

SEAM Index------------------

Register AssetFindAsset

ClassifyAsset

DocManager------------------

StoreDocGetDoc

ClassifyAsset

TextIndexer------------------

IndexDocQueryIndex

TestConsumerUI



Exercise #4 Interface: Services andOperations

• SEAMIndex Service (New Service and Functions) – AssetID RegisterAsset( string AssetAsText )

– AssetID FindAsset( string Title, string Author )

– bool ClassifyAsset( string AssetID, string Class)

• TextIndexer Service (Wraps Legacy Component) – Bool StatusFlag IndexDoc( string DocAsText )

– AssetID[] QueryIndex( string Title, string Author )

• DocManager Service (Wraps Legacy Component) – AssetID StoreDoc( string DocContent )

– string GetDoc( string DocID )

– bool ClassifyDoc( string DocID, string Classification )



Legacy Components API

• Supplied as C# Functions

– TextIndexerAppLibrary

• bool IndexTerms( string Content )

• String FindDocs( string Title, string Author )

– DocManagerAppLibrary

• string Store( string DocContent )

• string Retrieve( string DocID )• bool Categorize( string DocID, string Category )



Integrating Legacy Apps

• Download complete applicationsassemblies from class web site

– Integration Stubs available now

– Fully functional projects will be published nextweek

• Add as projects to your solution



Review for Mid Term Exam

• Review of the previous lectures

• Q&A for Chapters 1 – 9

• Review of Implementing Web Servicesand SOA Designs in VisualStudio/ASP.Net

• Additional Notes



SOA Implementation via WebServices in ASP.Net

• Exercise #1: Web Service Consumers – Web Reference

• What is it doing?

• What is its purpose?• Exercise #2: Building a Web Service

– What does a Visual Studio Web Serviceproject generate?

• Exercise #3: Publishing a Web Service – What is published to the remote site?



Additional Notes: ServiceOriented’ness

• When designing a service oriented architecture, askyourself: – Is communication among services and consumers like a phone

conversation or the exchange of standard forms

– If it is like a phone call interview, it is chatty and not serviceoriented.

• A service is being performed, but each interaction in the system isonly a piece of the complete service

– If it is like an exchange of standard forms, and all the informationrequired to perform the service is on that single initial form, and

the information required is returned in a equally complete singleform, it is service oriented

• Example: You need to determine if several checksyou’ve written have cleared the bank.



Not Service Oriented

• Call the bank, the operator ask what your needis.

• You respond you wish to verify if these checkshave cleared

• They ask you to identify your account and yourperson.

• They validate your identity and ask whichchecks: which numbers and what dates.

• You give them the check information, one checkat a time.

• They verify each one at a time.



Service Oriented

• You fill out a form which includes youraccount information, personal identifiers,the service you want performed (verify

checks have cleared), and the numbers ofthe checks.

• The response is another form listing the

state of all the checks you have asked tohave verified.



The Difference?

• They both perform the same businessprocess

• They both have the same accuracy andcompleteness

• One is a complete service performed inone single step, and is service oriented

• The other is performed by many relatedinterdependent steps, and is not



Summary• Session 7: 3/11/09

– Mid Term Exam

– Introduction of Class Week

• Spring Break the following week – Exercise #4 is due 3/25/09

– Specifications for Class Project will bepresented

Documents

S6 SOA Service Layers 030409 CH9