1. Distribuerte Systemer Viktigere enn vi tror, vanskeligere enn det høres Komponenttorget ‘99 Trondheim Trygve Reenskaug Numerica Taskon
Distaribuerte Systemer

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

3. 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
Distaribuerte Systemer
© Trygve Reenskaug 1999

4. Presentation plan
Communication-centered architectures A new system generation
The Collaboration
Remote Method Invocation (+ CORBA, COM)
The Component (+ Java Bean, Java Enterprise Bean)
Summary and Conclusion
Distaribuerte Systemer

5. CPU-Centered paradigm
Output
Input
Central
Processing
Unit
FORTRAN
Algol 60
Tape
Hardware
Software
Distaribuerte Systemer

6. 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
Distaribuerte Systemer

7. 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. ????
Hardware
Software
Distaribuerte Systemer

8. Summary - 1 Unlimited Scaling Distributed Ownership
Support people’s Tasks
Flexible Consistency Requirements
Fideikommiss hits
Distaribuerte Systemer
© Trygve Reenskaug 1999

9. Presentation plan The Collaboration Summary and Conclusion
Communication-centered architectures A new system generation
The Collaboration
Remote Method Invocation (+ CORBA, COM)
The Component (+ Java Bean, Java Enterprise Bean)
Summary and Conclusion
Distaribuerte Systemer

10. 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!
Distaribuerte Systemer

11. Network with Default Resource
The (toy) sample user interface is a Java Applet that is run from a web browser. The interface interacts with a background service that is also written in Java.
The top bars in the bar chart shows the earliest times when the activities can be performed. The bottom bars show when the activities can be done if all use the same resource, and this resource can only serve one activity at the time.
Distaribuerte Systemer
© Trygve Reenskaug 1999

12. Network with Gantry Resource
An example of specialization: Some activities use a Gantry crane. Our crane has two independent hooks: One can lift a light load and the other can lift any load.
Activity B is to lift a light load. It can be performed concurrently with activity C, which is a heavy load. Activities D and E are both heavy loads, they have to be performed in sequence. Activities A and F use the old resource that can serve one at the time.
Distaribuerte Systemer
© Trygve Reenskaug 1999

13. The objects and their message paths
WEB Browser
paint();
Button
Code is invisible!
Applet
ActivityGraph
Project
BarChart
Project
activity-B
activity-D
activity-A
Activity-F
activity-C
activity-E
Distaribuerte Systemer

14. Summary - 2 Move from closed to open systems
Distributed solutions
The object
has responsibility
knows its collaborators
is robust
Nobody knows everything!
Move from closed to open systems
Move from centralized to distributed control
Change focus from build-time to run-time aspects
Abstraction: The role the object plays in collaboration context
Distaribuerte Systemer

15. Presentation plan Remote Method Invocation (+ CORBA, COM)
Communication-centered architectures A new system generation
The Collaboration
Remote Method Invocation (+ CORBA, COM)
The Component (+ Java Bean, Java Enterprise Bean)
Summary and Conclusion
Distaribuerte Systemer

16. Java RMI Remote Method Invocation
WEB Browser
Client
Button
Server
App
ActivityGraph
Information Bus
BarChart
Project
activity-B
activity-D
activity-A
Activity-F
activity-C
activity-E
Remote access is slow and error prone.
Simplify and clarify!!!
Distaribuerte Systemer

17. RMI middleware (1 second can grow to 3 hours!!)
Client
Server
The
BarChart
object
The
ActivityGraph
object
The
Project
object
(A Server) An
Activity
object
(A server)
Project Stub
represents
the Project
Activity
skeleton
represents sender
Activity Stub
represents
an Activity
Information Bus
Project
skeleton
represents sender
Java Naming & RMI Services (or CORBA or COM)
HTML - web page language
TCP/IP - Guaranteed end-to-end data stream
Physical communication (ISDN/Ethernet/….)
Distaribuerte Systemer

18. Presentation plan The Component (+ Java Bean, Java Enterprise Bean)
Communication-centered architectures A new system generation
The Collaboration
Remote Method Invocation (+ CORBA, COM)
The Component (+ Java Bean, Java Enterprise Bean)
Summary and Conclusion
Distaribuerte Systemer

19. Why use components Use componets to Simplify remote communication
Avoid coding to save time
Avoid coding to increase quality
Use tools to increase your productivity
Get transactions, security, etc. for free
Distaribuerte Systemer

20. What is a Component Tools are used to compose systems
A component is reused by cloning
A Component is an object playing standardized roles
A Component is a reusable object
Technology
System user
System composer
Component creator
Tool developer and vendor
Component environment standardizer
Organization
Distaribuerte Systemer

21. Compose User Interface with Java Beans
Distaribuerte Systemer

22. Bean object plays several roles
BeanBox
Composer
Use Case
Run-time display
Use Case
App
Bean Object
Distaribuerte Systemer

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

24. Presentation plan Summary and Conclusion
Communication-centered architectures A new system generation
The Collaboration
Remote Method Invocation (+ CORBA, COM)
The Component (+ Java Bean, Java Enterprise Bean)
Summary and Conclusion
Distaribuerte Systemer

25. 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.
Distaribuerte Systemer

26. 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
Distaribuerte Systemer

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

28. You can do it! http://www.ifi.uio.no/~trygve Distributed systems
Distaribuerte Systemer

29. Kaffe
Distaribuerte Systemer