Course on Middleware Systems

Outline

Middleware concept
Database Integration
Web development (Meta HTML)
Transaction Processing (Open communication, write/read and finally commit)
Components

I. Middleware concept

I.1 What Middleware actually used for?

Middleware achieves essentially three things:

Heterogeneous system integration
Interoperability of these systems
Portabilty of these systems

I.2 Distributed system

One system is said distributed if its components are distributed or physically a part from one another.
Example: Interconnexion of one machine with a Database (via net).

I.3 Middleware Platform

CORBA : Common Object Request Broker Architecture (for UNIX/Linux)
DCOM : Distributed Component Object Model (for Windows NT)
DCE : Too old!!

Remarks : Middleware does not mean obligatory CORBA or DCOM. In fact, DCOM must be the good solution for Microsoft products and CORBA must be the good one for Linux.

Some vocabulary:

RPC : Remote Procedure Call
RMI : Remote Method Invocations (Object oriented)
IDL : Interface Definition Language. It serves to describe the interfaces.
stub-compiler : Compiler which gives an Interface (Java or C++).

I.4 Distributed system. Application case studies

First Idea : Middleware helps the programer to develop the Distributed system.

Case I: Applying CORBA to medical imaging.

There are many different hardware resources in the medical center (PC, Fax, ...) and the programer must coordinate these systems.
Middleware help him to give an abstraction for these systems.
The doctor wants one radiography before one another, and the programer must resolve this problem of priority (priority's problem).
Middleware offers to the programer a concept of these priority.

Case II: Applying CORBA to real-time avionics

The aeroplane must to communicate at the same time with different satelites and with the control tour.
Real-time : There are two stages of real-time:

Express priority (low latency -> High Performance)
The execution (One process can be executed at t1 and one another can be execute at t2 (t1)).

Middleware allows the programer to order these executions and allows him to realize the deadlines. In fact, middleware supports real-time.

Case III: Applying CORBA with Database

Middleware touchs upon :

Distributed systems
Operating systems
Database systems (DB integration)
Networking
Programming language