Information system : Introduction to MERISE and MCD

Information system : Introduction to MERISE and MCD

 1. The information system:

 The information system or IS can be defined as the set of human, material and immaterial means used to manage information within a unit, such as a company.

Information system to manage informations

However, an information system should not be confused with a computer system. Indeed, information systems are not always fully computerized and already existed before the arrival of new information and communication technologies, of which information technology is an integral part.

The IS has 4 essential functions:

* The capture or collection of information.
* Storing information using a file or database. 
* The processing of information in order to better exploit it (consultation, organization, updating, calculations to obtain new data, ...). 
* Dissemination of information.

Formerly, information was stored on paper using forms, records, ... and there were manual procedures to deal with it. Today, computerized systems, such as relational database management systems (RDBMS), are used by the information system.

2. MERISE:

 

MERISE is a French method born in the 70s, initially developed by Hubert Tardieu. It was then promoted in the 1980s at the request of the Ministry of Industry, which wanted an IS design method.

Merise method effective

MERISE is an IS analysis and design method based on the principle of separation of data and processing. It has a number of models (or diagrams) that are spread over 3 levels:

    *  The conceptual level,
    * The logical or organizational level,
    * The physical level.

In this course, we will be interested only in certain schemas allowing the design of a relational database and then its realization on a RDBMS.

3. Conceptual Data Mode :

This is the development of the Conceptual Data Model (MCD in french), which is a graphical and structured representation of the information stored by an IS. The MCD is based on two main notions: entities and associations, hence its second name: the Entity / Association scheme.

The development of the MCD involves the following steps:

    *  The implementation of management rules (if these are not given to you),
    *  The development of the data dictionary,
    * The search for functional dependencies between these data,
    * The development of the MCD (creation of entities then associations and addition of cardinalities).