1. Komponentbasert utvikling Den sanne objektorientering
Trygve Reenskaug
Numerica Taskon
UML Unified Modeling Language og komponentbasert utvikling Geilo 19 april 1999
Komponentbasert utvikling

2. Personal Information Environments Content and Communication
Digital
Map
Census
Data
Police
Records
House
Drawings
Aerial
Photos
Police Dispatcher
Komponentbasert utvikling
© Trygve Reenskaug 1999

3. Presentation Plan The Communication-Centered Paradigm
Building Systems with Components
But the Real Challenge is … Summary and conclusion
Komponentbasert utvikling

4. CPU-Centered paradigm
Output
Input
Central
Processing
Unit
FORTRAN
Algol 60
Tape
Hardware
Software
Komponentbasert utvikling

5. Storage-Centered paradigm
Shared
database
App.1
App.2
App.4
App.3
DB Schema language
e.g. Entity-Relation
e.g. NIAM
Output
Input
Memory
Central
Processing
Unit
Disk
Tape
Hardware
Software
Komponentbasert utvikling

6. Communication-Centered paradigm
Object 1
Object 2
Object 4
Object 3
Information Bus
Central
Processing
Unit
Input
Output
Disk
Communication Bus
Memory
Tape
Composition language
e.g. Object Constraint Language
Hardware
Software
Komponentbasert utvikling

7. No Main Program! Centralized solutions The designer sees everything
knows everything
understands everything
controls everything
The SYSTEM
Distributed solutions
The object -
has responsibility
knows its collaborators
is robust
Nobody knows everything!
Komponentbasert utvikling

8. Advantages Communication-Centered paradigm
Unlimited Scaling
Distributed Ownership
Support people’s Tasks
Flexible Consistency Requirements
Fideikommiss hits
Komponentbasert utvikling
© Trygve Reenskaug 1999

9. Presentation Plan Building Systems with Components
The Communication-Centered Paradigm
Building Systems with Components
But the Real Challenge is … Summary and conclusion
Komponentbasert utvikling

10. App. for booking meeting rooms
Komponentbasert utvikling

11. We use objects to master the age of distribution
Object-B IN
OUT-B
OUT-C
Methods
Variables IN
OUT-C
Object-C
Methods
Variables
Object-A IN
Methods
Variables
Message
triggers method
causes response
Komponentbasert utvikling
© Trygve Reenskaug 1999

12. What is a Component? A Component is a reusable object
A Component is an object playing standardized roles in a specified container
A component is reused by cloning
Tools are used to compose systems
Komponentbasert utvikling

13. Application Assembler (User expert)
Component Value Chain
Application Assembler (User expert)
Component Deployer (Operational environment expert)
Component Provider (Domain expert)
Component Container Provider (System programmer)
Komponentbasert utvikling

14. The competing technologies
CORBA™ Object Management Group (OMG) Public standards
Java™ SUN Microsystems Build once, run anywhere
COM™ Microsoft Dominating on desktops
Komponentbasert utvikling

15. Component standardization examples
Information Bus
Java Bean
User Interface
Properties
Events
Composition
Run time context
Enterprise Java Bean
Naming
Persistence
Transactions
Security
Load sharing
Run time context
Client
Server
Komponentbasert utvikling

16. Compose User Interface with Java Beans
Komponentbasert utvikling

17. The Enterprise Java Bean objects and their message paths
Multithreading
Reuse EJBs
Reuse DB conn.
Persistence
WEB
Browser
Name
Server
Booking
Home
1: lookup("roombooker");
Booking
Object
2: create(xx);
3: ejbCreate(xx);
Could be Entity Bean
Information Bus
Booking
Client
Booking
Bean
java.sql. Connection
4: getRooms();
Room Chooser
Java Bean
5: getRooms();
Session Bean
6: addItem(element)
Transactions
Security
Komponentbasert utvikling

18. EJB Implementation We wrote:
BookingHome.java Intf. Client create its own server object
Booking.java Intf: Client access booking service
BookingBean.java Class: The booking business logic program itself
BookingClient.java Class: The main user interface class
The IONA EJBHome tool created these files for us:
RoomBroker.ejbml Property file describing the booking EJB
datasource.properties File: Maps datasource names to JDBC databases URLs.
ejbhome.properties File: EJB Server configuration
Iona*.java/class Class: A number of supporting java classes
Komponentbasert utvikling

19. Presentation Plan But the Real Challenge is … Summary and conclusion
The Communication-Centered Paradigm
Building Systems with Components
But the Real Challenge is … Summary and conclusion
Komponentbasert utvikling

20. Distributed Systems What you get: Unlimited scaling
Distributed ownership
Specific task support
Information partitioning
How you do it:
Think in terms of objects, their responsibilities and collaboration.
Think in terms of open systems, no main program.
Komponentbasert utvikling

21. Component-based development
What you get:
Build by composing library objects, avoid coding.
Leverage infrastructure mechanisms (transactions, security, persistence,…)
How you do it:
Think in terms of objects. (Responsibilities, environment, collaboration.)
Penetrate vendor fog - find essentials
Insist on high product quality
Adapt to new layers in value chain
Komponentbasert utvikling

22. The main problems
We spend too much time and effort on low-level mechanics.
Current offerings are NOT:
Easy and intuitive to use
Smooth development platforms
Reliable
Secure
Extensible
Komponentbasert utvikling

23. The Connected Organization
The Real Challenges
The Connected Organization
Effective
Partitioning of
Information
Services
Effective,
Enjoyable
and
Instructive
Tools
Business processes
Task / Use Case / Tool
Information services
Komponentbasert utvikling
© Trygve Reenskaug 1999

24. Do it! http://www.ifi.uio.no/~trygve Distributed systems
Komponentbasert utvikling