EFFECTS OF DATA MODEL AND TASK CHARACTERISTICS ON DESIGNER PERFORMANCE - A LABORATORY STUDY

A laboratory experiment was conducted to compare designer performance in modelling user views using the relational and the entity relationship models. A user view is a form or a report used in an information system and is one of the sources of user requirements. Previous studies have not considered the effect of user view characteristics on designer performance. This study considered nine user views, which varied in two task characteristics: degree of nesting and derivation span. Degree of nesting is the number of nests in a user view, where a nest pertains to a group of attributes that is multivalued with respect to another group of attributes. Derivation span refers to the presence of attributes from different objects in the same view. Three levels each of degree of nesting and derivation span were considered. Subjects enrolled in a database class were trained in one of the two modelling approaches and were asked to conduct conceptual database design of a specified problem. Each view was graded using a predefined scheme. Results indicated that subjects using the entity relationship model took longer to complete the task but outscored subjects using the relational model. The degree of nesting emerged as a significant predictor of scores. The derivation span also seemed to account for the variation in scores although the effect was not statistically significant. The findings suggest that for novice designers the entity relationship is the appropriate choice for modelling user views. Further, the degree of nesting is an important indicator of the complexity of the user view.