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 relationsh ip models. A user view is a form or a report used in an information sy stem and is one of the sources of user requirements. Previous studies have not considered the effect of user view characteristics on designe r performance. This study considered nine user views, which varied in two task characteristics: degree of nesting and derivation span. Degre e of nesting is the number of nests in a user view, where a nest perta ins to a group of attributes that is multivalued with respect to anoth er group of attributes. Derivation span refers to the presence of attr ibutes from different objects in the same view. Three levels each of d egree of nesting and derivation span were considered. Subjects enrolle d in a database class were trained in one of the two modelling approac hes and were asked to conduct conceptual database design of a specifie d problem. Each view was graded using a predefined scheme. Results ind icated that subjects using the entity relationship model took longer t o complete the task but outscored subjects using the relational model. The degree of nesting emerged as a significant predictor of scores. T he derivation span also seemed to account for the variation in scores although the effect was not statistically significant. The findings su ggest that for novice designers the entity relationship is the appropr iate choice for modelling user views. Further, the degree of nesting i s an important indicator of the complexity of the user view.