OVERVIEW

In the previous chapter, we described how data quality can be incorporated into the relational model. To achieve data-quality-by-design, it would be useful to incorporate data quality attributes at the conceptual design stage of a database application. Conventional conceptual data models and their corresponding design methodologies, however, have been developed to capture entities, relationships, attributes, and other advanced concepts such as is-a and component-of relationships. Data quality is not explicitly recognized. The task of incorporating data quality into the design of a database application is left to the designer. Consequently, some database applications capture data quality attributes whereas others don't.

Indeed, Chen [ ^[1]] stated that: "Most data models (including the ER model) assume that all data given is correct. We need a scientific way to assess the quality of the data in (or to be put into) the database. We also need to incorporate such quality measures into the Entity-Relationship (ER) model as well as to develop algebra- or calculus-based operations to manipulate such data quality descriptions."

This chapter presents a Quality Entity Relationship (QER) model ^[4] proposed by Storey and Wang [ ^[6]] that incorporates data quality requirements into the database design process. The procedure for doing so involves differentiating application quality requirements and data quality requirements from application requirements, and then developing the constructs and procedures necessary to represent the data quality requirements in an ER.