An Application-Programming Interface or API provides a set of program functions that can be used to build new applications. In this paper, we study how to use the expectation-confirmation theory (ECT) to identify API usability problems, and what obstacles a novice developer faces when learning a new API and its accompanying development tools. We conduct a study over the impact of using a visual editor on API usability and then use the expectation-confirmation theory to study perceptions about the API and the editor. We finally present a list of obstacles found in the study that can be used by others to create more usable APIs and development tools.

Graphical information system (IS) models are used to specify and design IS from several perspectives. Due to the growing size and complexity of modern information systems, critical design information is often distributed via multiple diagrams. This slows search performance and results in reading errors that later cause omissions and inconsistencies in the final designs. We study the impact of large screens and the two promising visual integration techniques of elision and connecting lines that can decrease the designers' cognitive efforts to read diagrams. We conduct a laboratory experiment using 84 computer science students to investigate the impact of these techniques on the accuracy of the subjects' search and recall with entity-relationship diagrams and data flow diagrams. The search tasks involve both vertical and horizontal searches on a moderately complex IS model that consists of multiple diagrams. We also examine the subjects' spatial visualization abilities as a possible covariant for observed search performance. These visual integration techniques significantly reduced errors in both the search and the recall of diagrams, especially with respect to individuals with low spatial visualization ability.

Current CASE tools lack efficient techniques to visualise information system (IS) design repository. One important aspect in visualising graphical IS models is to preserve structure, which can have semantic value. Another key issue is to provide both focus and context in order to understand how detailed information relates to other design elements. The third aspect to consider is to trace between diagrams and other design documents. Our VRML implementation integrates different types of diagrams as a whole. We applied elision technique for decomposition of data flow diagrams (DFD) and added visible lines to link parts of DFD to entity-relation diagrams. In our laboratory experiment, we collected users' subjective opinions and performance in information search tasks. Based on the promising results, we give suggestions for further exploration.