Project Title:Cobra Implementation on

Association Service

What is Association Service?

• “Association” is simply a mapping from a key to a value

• “Association Service” is a service provided by the system for this mapping.

Application of Association Service

• on-line grammar learning service

• telecommunication interfaces for deaf people

• searching engine in internet

Data Type of “Key” and “Value”

• The “Key” is in a string type.

• The “Value” is an array of bytes

The format represented by “value”

• Simple text(single byte or double byte)

• image

• audio

• video

Why CORBA ?

• It is more difficult for a programmer to develop an application in distributed environment than in a single machine.

• CORBA is A middleware designed by OMG to help a programmer to develop application in distributed system

• CORBA may let server location be transparency to the client by its naming service

How to implement CORBA

It needs an ORB(Object Request Broker) for CORBA implementation

ORB available?

• Iona's Orbix

• JavaSoft's Java IDL

• Visigenic's VisiBroker for Java

The Link between Object Implementation and ORB• By Object Adapters

What is Object Adapter

• It is a component that an object implementation at server side reports its availability for request to ORB

• ORB uses it to manage the run-time environment of the object implementations

Currently Developed Object Adapter• Two interfaces developed by CORBA:

• 1) Basic Object Adapter (BOA)

• 2) Portable Object Adapter (POA)

Programming Steps for CORBA Implementation

• Design on IDL• Compile IDL file to generate stub code for

client program and skeleton code for server program

• coding for object implementation• coding for client program• compile client and server program and then

running both server and client program

Functions of the System

• Construct an association

• Seeking an association

• Delete an association

Access Control

• Access Control List

• Capability

Construction of Capability

Capability = Fn(User Name, ID, Access Right, Random0)

Password = Capability + ID

(64 bits) (32 bits) (32 bits)

Different Kinds of Capability generated by the system:

• New Capability

• Restricted Capability

Structure of the system

• Tuple (id, key, value, size, value type)

• List : Link up the tuple

• Hash table : index to the 256 lists

Permanent Storage of Association

• Storing in a series of Unix files

• Storing in database– Oracle Server

– JDBC

Recovery of Association

• Permanent table

• Temporary table• add a flag to indicate the kind of manipulation

– add association

– delete association

• output information to the system when it is waken up again

• empty if normal procedure for closing system

Conclusion

• Association Service is simple but practical

• It makes the programming be much easier in distributed environment via CORBA implementation

• It still has more features for the further development of this system

Further Development

• Develop client side of the system as an applet

• Adding more interface for various format of "value”

• Multi-users supporting

• Directory service as a yellow page

The End.Thank you!