Component Based Systems Analysis

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Component Based Systems Analysis
IS7 VT99

• Introduction

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Why Components?

• Development alternatives
• In-house software
• Standard packages
• Components

60 of the functionality in a typical
information system is the same for
all organisations (IBM)
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What is a Component?

• A component is a piece of software small enough
  to create and maintain, big enough to deploy and
  support and with standard interfaces for
  interoperability (Jed Harris)
• Components are executable

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Component Models

• Standard specification of how components should
  behave in a given environment
• Versioning
• Open tool palettes
• Configuration management
• Event notification
• Metadata and introspection
• Licensing

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Levels of Components
Insurance
Telecom
Aerospace


Subscriber Telephone service
Domain Components
General Business Components
Customer, Product, Order, Currency
Technical Components
GUI components Security services
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Component Based Development
Supply - Build new - Wrap
existing - Buy
Consume - Assemble
applications
Manage
- Publish
- Subscribe
- Catalogue
- Browse
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Objects and Components
Analysis Design
Construction



Object oriented



Component based
A component does not have to be an object
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Client/Server Architecture
A server providing services A client requesting
services
ATMs
Thin and fat clients
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Advantages of Client/Server

• Scalability
• Horizontal, more clients
• Vertical, more powerful server
• Dedicated servers
• Shared resources
• Maintenance
• Server centrally
• Client locally

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Three Level Architecture
User interface provided via a browser
Presentation
Java servlets running on a server
Application logic
Data
Data served from a DBMS
Handles data from different sources within
client/server
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Distributed Objects

• Objects encapsulate data and operations
• Ordinary objects
• Reside in a single program
• Cease to be separate entities after compilation
• Distributed objects
• Reside anywhere on a network
• Exist as physical standalone entities
• Accessible by other objects

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Middleware

• Distributed software for supporting interaction
  between client and server including client API,
  network transfer, and server response
• Database middleware ODBC, JDBC,
• Internet middleware HTTP,
• Object middleware CORBA, COM/DCOM, Enterprise
  JavaBeans, ...

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OMG Object Management Architecture
Application objects
Common facilities
Object Request Broker
Object services
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Architectural Patterns

• Context
• Designing a living room
• Problem
• Making people feel comfortable
• Forces
• People want to sit down
• People want to be close to the light
• Solution
• Put a sitting place close to the windows

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Design Patterns

• Context
• Developing software with a human-computer
  interface
• Problem
• Interfaces vary often
• Forces
• Easy to modify the interface
• Modifying the interface should not impact the
  application logic
• Solution
• Model-View-Controller

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A Design Pattern - MVC
Model
core data
notify getData
View
myModel
display update
Controller
myView
handleEvent update
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Properties of Patterns

• Address recurring problems
• Document well-proven experience
• Specify abstract solutions

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Analysis Patterns
Person
Employment
Organisation
Period of Time
A person is employed in an organisation for a
period of time.
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Analysis Patterns
Person
Management Role
Organisation
Period of Time
A person has a certain management role for a
period of time.
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Analysis Patterns
Marriage
Person
Period of Time
Two people are married for a period of time.
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Analysis Patterns
One party is accountable to another party for
something for a period of time.
Accountability type
Organisation
Accountability
Period of Time
Organisation
Person
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Course contents
Analysis patterns Fowler
Component models JavaBeans SanFrancisco
DOT Java Servlets EJB CORBA COM/DCOM