Schematization as an aid to organizing zog information nets

ZOG is a system for human-computer communication, characterized by a rapid-response, menu-selection interface to a large, network-structured active database. The problem of entering information into a ZOG network is significant. One paradigm that has emerged informally is Top Down Frame Construction. As part of this approach, the builder of networks is encouraged to employ schemas in designing and extending an information base. A schema is a piece of the network with some parts identified as constants, and others as variables. Schemas can be instantiated; when this happens, the variables in the schema are assigned appropriate values. SKED is an augmentation to ZOG for exploring the functionality and effective use of these schemas in the construction of a ZOG network. We describe a schema mechanism and functions to exploit it provided by SKED, and show how SKED can be used to implement of a variety of complex information systems. We develop "engineering models" of the use of SKED and ZOG. One such model, called the Frame-Aggregated model, predicts the total time taken by the user to perform a large task. We validate this model by collecting data from two users of ZOG and SKED, and compared the two systems. Another model in terms of Goals, Operators, Methods and Selection Rules (called a GOMS model by {Card, Moran, and Newell 76}) was developed and applied to data collected on the use of SKED by one subject. From this, we obtain parameters that describe this subject. These parameters were related to certain parameters required in the frame-aggregated model--as a result, we can predict them and estimate the effect of improving system response on the total task time predicted by the frame-aggregated model. The design of SKED from ZOG required that we make many decisions about the system that closely affected the performance and capabilities of the system. We report on this design study by making a set of assertions about capabilities that ZOG/SKED lacked and how they affected the implementation of other features of SKED. These assertions constitute a set of proposals for redesigning the ZOG system, as well as a collection of rules of thumb that would be useful for a system designer.