Presentation Middleware, Assignment 4.5

1. What is Middleware?

2. How is a database connection between a client and a server established?

3. What is the advantage of ODBC?

What is Middleware?

Middleware is software that runs between client and server processes. It is the "glue" between the client and server, which makes it possible for them to communicate to each other. Middleware is written in such a way that the user never notices it's presence. It delivers secure and transparant services to users.

There are several types of middleware services.


The situation at our School

According to our system administrator our school uses a Microsoft SQL Server to store data about user accounts into a database. The system administrator uses a Windows 95 Client to manipulate the database. The SQL server runs on a Windows NT machine, which is located somewhere in the building.

When you observe this situation you might think that you only need a client running on your local machine and a server application running on the server to manage the database. But if you take a closer look, you see that this is not true. In fact you need:


How is a database connection between a client and a server established?

In this section we describe how the connection between a client and a server is established. If you want to communicate between the client and server than both machines must run ODBC drivers to communicate with each other.


The Client/Server Model


Remote Request

What happens if someone wants to perform an operation on the database server? In this example the DBMS, Database Management System will convert the client's request to perform an operation on the database server.

A simple remote request

What is the advantage of ODBC?

ODBC stands for Open Database Connectivity. It is a standard which makes it is possible for any database application that supports ODBC to manage the databases which also supports ODBC with for example SQL statements.

Once you have the ODBC driver in place users can gain immediate access to your DBMS. If you write an application which supports the ODBC standard, you don't have to worry about how to approach the database. For instance: A Microsoft Client Application which supports ODBC can communicate with an Oracle Database which also supports ODBC. ODBC makes sure that the commands are converted in a proper way.

Overview of ODBC


Except the hardware necessary to make a network connection you need software, that supports the RDA protocol if you want make a database connection between a client and a database server. In most cases an ODBC driver is used.



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