Download - Analysis & Design Method for OSGi-based Development

www.mimos.my © 2008 MIMOS Berhad. All Rights Reserved.

[email protected]

Azrinsyah Mirza Asfian, Engineer at MIMOS Berhad

Analysis and Design Method for OSGi-based Development

• Introduction• Service-Oriented Programming and OSGi• Object-Oriented Analysis and Design Method• The Proposed Method

– Analysis and Design Method– Example– Applying the Analysis and Design Method to the Case Study

• Conclusions and Discussions

Agenda


• OSGi – Open Services Gateway Initiative – technology defined and promoted by the OSGi Alliance– open specifications for network delivery of managed services to

local networks and devices.• Service-orientation and component-orientation

– requirements of having a new analysis and design approach– existing OOAD methodologies e.g. Booch, OMT and UML could

not be applied directly• Proposes an analysis and design method for OSGi-based

development

Introduction


• Utilizes services as fundamental elements• In OO, objects are building blocks while in SO, services

are its foundation blocks• A service embedded in some component

– accepts one or more requests and returns one or more responses

• Different from traditional methods, e.g. OO or structural• Remarkable traits

– Dynamism– Substitutability

• Discover and substitute at run-time• Focuses on how services are described and organized of

appropriate services at run-time

Service-Oriented Programming


Service-Oriented Interaction Pattern


• OOP– problems can be modeled in terms of objects in the problem

domain• SOP

– problems can be modeled in terms of services which can be implemented and provided by any other components, based solely on the contract

• SOA– can discover, substitute and co-ordinate service

implementations at run-time – because components publish and use services in a P2P manner

Service-Oriented Programming (cont.)


• Fosters code reuse • Rapid and dynamic system construction• System upgrade without restarting and • Independence from platforms, protocols and deployment

environments

Contributions of Service-Oriented Programming


• Follows concept of SOP • OSGi spec defines the service framework

– minimal component model – management service for the components– service registry– Initially used for service gateways– now, mainstream software devt e.g. Eclipse subproject called

Equinox• Services (i.e., Java interfaces)

– packaged along with implementations and associated resources into bundles

– conforms to SO interaction pattern– deployed into the OSGi framework via WANs i.e., the Internet or

other means e.g. GSM or memory cards.

OSGi Concepts

© 2008 MIMOS Berhad. All Rights Reserved.

• Bundle is a Java JAR file that contains– physical unit of deployment– can be modified and updated without requiring system to be

restarted– some combination of Java class files – native code– associated resources– manifest - meta-data describing, Java packages that the bundle

requires or provides• Other competing SO architectures are NetBeans module

and Java Plugin Framework

OSGi Concepts


• Steps available in both Booch and OMT:1. Develop a problem statement2. Identify the classes and objects3. Identify the semantics (or attributes) of these classes and

objects4. Identify the relationships among these classes and objects5. Specify the interface and then the implementation of these

classes and objects

General Object-Oriented Analysis and Design (OOAD) Method


• An improvement over existing OOAD methods. • Additional steps added:

– Extract or reuse existing OSGi services and components (or bundles) based on their versions

– Determine dependencies between services– Depict dynamic view of the system using service dependencies

diagram

The Proposed Method


• The resulting steps:1. Develop a problem statement2. Identify the services based on their intended responsibilities3. Identify relationships between services during runtime.4. Identify bundles that encapsulate a service (or services)5. Identify classes and objects that make up a particular service

and bundle6. Identify the semantics (or attributes) of these classes and

objects7. Identify the relationships among these classes and objects8. Specify the interface and then the implementation of these

classes and objects

Analysis and Design Method


• Illustrate how to translate software requirements into design using OSGi

• The requirements associated with this software:– System must be able to display all users available– When a user is selected, system must open a screen that

displays details of the user.– All user information must be stored inside a centralized

database.– System resides on a client computer which is remote from server

that stores all the user information.

Example


Applying the Analysis and Design Method – Overall System Architectural Diagram


• Step 2 of the method is applied to the requirement specifications

• Services identified:– Profile Persistence Service: Responsible in making used of Java

persistence classes to perform Read operation on profile of users residing in centralized database

– User Detail Screen Service: Provides a screen to open detail of a selected user

– Main Screen Service: Shows the screen of main application– Table Screen Service: Provides table screen service

Applying the Analysis and Design Method – Step 2


Applying the Analysis and Design Method – Step 3, Service Dependencies Diagram


• Applying step 4 – results in each of the services to be in their respective bundles – need not to depict this– in complex systems where a bundle can provide more than one

services, it is necessary to have a diagram on its own• Step 5 onwards will not be discussed here

– same steps likewise OOAD methods– design patterns can be applied to further promote reusability

within a bundle

Applying the Analysis and Design Method – Step 4 and Step 5


• Suggested approach or step-by-step guidelines to build software systems utilizing OSGi

• Weaknesses of this method are:– No formal notation defined to depict relationships between

services during runtime– System architectural diagram must be depicted upfront– Identification and decompositions of services largely depends on

skills and experience• A trend moving towards MDA and MDD is currently

underway by OMG • In the future, this method can be improved to follow

such a trend

Conclusions and Discussions


THANK YOU


• In 1990s OO paradigm became popular– OO languages have been the preferred programming language– OO paradigm has introduced attributes which solve issues in

structured paradigm• OOAD method

– invented, likewise the structured analysis and design method is for structured paradigm

– step-by-step guidelines for architects and developers on designing and developing their applications

– popular methods e.g. Booch, Object Modeling Technique (OMT) and the Unified Modeling Language (UML)

Object-Oriented Analysis and Design (OOAD) Method


• Analysis and design of OO systems only• Resulting design is usually monolithic• Invented in 1990s where service-oriented and

component-oriented paradigm was not common• An improved version of OOAD method is required• Do not cater for dynamism

– service required or depended on by another service becomes unavailable

– all components must be made available for the dependent components to be able to run or use

– in SO, requires handling of unavailable service to be clearly specified during analysis and design phase

OOAD Issues


• UML does not provide formal notations to depict services• Structural view

– bundle diagram that shows relationships and dependencies against other bundles

– class diagram can still be used to illustrate classes within a package in a bundle

• Dynamic view – OSGi bundle together with services that it offers to other

services residing in other bundles– ensure that system being designed has all required services to

be resolved and available during runtime

OOAD Issues (cont.)


• OSGi attributes– possibility that different versions of same package providing a

service to be made available– different versions of this package might be providing same

service with different behaviours– Different parts of system might be using different versions of

same package• Dynamic view of entire system is depicted by service

dependencies diagram• Version of a service must be specified so that dependent

services can be connected• Reactive approach in system development do exists

OOAD Issues (cont.)


• Booch and OMT clearly specify the steps required to be taken when converting system requirements into a software design

• UML– does not specify the exact method– only specify the notations and type of diagrams available to

provide different architectural views of a software system– designed to be compatible with those methods– methods have been recast to take advantage of the new

notations available

OOAD Method (cont.)
