Relational Modeling Advantages over the E-R Approach

Carlos Caldeira, University of Evora, Portugal


1. INTRODUCTION

In 1970, E.F. Codd defined a Relational Model of databases to address the shortcomings of existing information systems. The Relational Model is the most important concept in the history of database technology because it provided a structured model for databases. The result is that this concept has been applied as a powerful solution to almost all database applications used today. Relational databases are at the heart of applications requiring storing, updating and retrieving data, and relational systems are used for operational and transaction processing.

Six year later Peter Chen proposed an Entity Relationship (E-R) modeling theory that was widely accepted. One of the reasons why E-R model become so popular is the clear and appellative graphical format of entity relationship diagrams. But currently there is no standard notation for E R diagrams. Most of the differences are on different symbology applied to entities, weak entities, attributes and cardinality specification.

The supporters of E-R model techniques claims that the design of the database schema is straightforward: each entity becomes a table, attributes become columns, and relationships are represented by joining the primary-key and foreign-key columns together at run time. But unfortunately we know that it is not the case. In order to the E-R model catch some of the functions and data fluxes of real word, the model acquire a large number of extensions. Some have become very popular and widely spread, such as composite attributes, subclass and super class, generalization, dependency and classification [2], [3]. Therefore there are a high number of ER dialects.

In traditional database design the E-R model is used to develop a conceptual schema and from this schema is derived a relational database model [1]. In the academic and working worlds there is a common sense that follows a rule, almost sacred and never questioned that point to the E-R model as being the first step of any relational database development.

We are now conducting classrooms experiments comparing the performance and quality of projects on students that are told to follow a direct approach in database design, bypassing E-R modeling and doing all database sketches directly from the relational model.

2. CONCLUSIONS

Even if it is certainly that any conceptual model cannot capture the real world restrictions, the limitations of the E-R model are too obvious, especially in more demanding applications. Therefore we are trying to demonstrate that teams that follow a direct approach on data modeling would get advantage over those that do the classic E-R model to Relational Model way.


Keywords: relational model, databases, e-r modeling