HCI
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Building a user-derived interface
Many human-computer interfaces are designed with the assumption that the user must adapt to the system, that users must be trained and their behavior altered to fit a given interface. The research presented here proceeds from the alternative assumption: Novice behavior is inherently sensible, and the computer system can be made to adapt to it. Specifically, a measurably easy-to-use interface was built to accommodate the actual behavior of novice users. Novices attempted an electronic mail task using a command-line interface containing no help, no menus, no documentation, and no instruction. A hidden operator intercepted commands when necessary, creating the illusion of an interactive session. The software was repeatedly revised to recognize users' new commands; in essence, the interface was derived from user behavior. This procedure was used on 67 subjects. The first version of the software could recognize only 7 percent of all the subjects' spontaneously generated commands; the final version could recognize 76 percent of these commands. This experience contradicts the idea that user input is irrelevant to the design of command languages. Through careful observation and analysis of user behavior, a mail interface unusable by novices evolved into one that let novices do useful work within minutes.
Training wheels in a user interface
New users of high-function application systems can become frustrated and confused by the errors they make in the early stages of learning. A training interface for a commercial word processor was designed to make typical and troublesome error states “unreachable,” thus eliminating the sources of some new-user learning problems. Creating a training environment from the basic function of the system itself afforded substantially faster learning coupled with better learning achievement and better performance on a comprehension post-test. A control group spent almost a quarter of their time recovering from the error states that the training interface blocked off. We speculate on how this training strategy might be refined, and more generally, on how function should be organized in a user interface.
Data that are missing, lost, or incomplete can be very significant in certain situations. Programs and languages need to be able to identify and manage such data effectively.
Audit trail compaction for database recovery
Total elapsed recovery time from disk-based database corruption can be shortened by reprocessing the audit trail off-line and thereby avoiding excessive resource utilization penalties. Using a bit map, the audit trail is compacted by eliminating irrelevant or superseded records. The compacted trail is then partitioned, and the partitions are processed in parallel.
Where can you find a solid, forthright overview of the computer systems and management behind airline reservations? NASA's space shuttle? Or any of the multitude of other large computer systems that support important projects or national activities? It's hard, sometimes impossible: partly because the people who worked on such systems often do not have the time to write about their experiences: and partly because many professional journalists who interview these people do not have the technical background to ferret out answers to the fundamental design questions addressed in these systems.
File organization: implementation of a method guaranteeing retrieval in one access
A new file organization method that guarantees retrieval of any record in one access is tested on two existing files, producing empirical results that compare favorably with theoretical predictions. The description of the method includes the algorithms used for implementing the required hashing and signature functions.
A large font virtual terminal interface: a software prosthesis for the visually impaired
A large font software interface running under UNIX1 is of great assistance to the severely visually impaired in the interactive use of computers. The interface, which functions as a virtual terminal as far as other processes are concerned, displays all characters (both user and system generated) at user-selectable degrees of magnification, yet is compatible with any standard CRT/keyboard terminal.
Talking to UNIX in English: an overview of UC
UC is a natural language help facility which advises users in using the UNIX operating system. Users can query UC about how to do things, command names and formats, online definitions of UNIX or general operating systems terminology, and debugging problems in using commands. UC is comprised of the following components: a language analyzer and generator, a context and memory model, an experimental common-sense planner, highly extensible knowledge bases on both the UNIX domain and the English language, a goal analysis component, and a system for acquisition of new knowledge through instruction in English. The language interface of UC is based on a “phrasal analysis” approach which integrates semantic, grammatical and other types of information. In addition, it includes capabilities for ellipsis resolution and reference disambiguation.
Laser optical disk: the coming revolution in on-line storage
Commercially available only recently, the optical disk drive uses a laser beam to burn impressions onto a plastic disk. Employing a highly focused beam rather than a diffuse magnetic field to write, the laser optical disk drive yields storage densities up to 10 times those of magnetic disks.
Updating a database in an unsafe environment
Normally, when an application makes use of a database, considerable resources are invested in maintaining the integrity of that database. However, in situations where use of a database may be desirable even though the normal level of resources is unavailable, a simple technique using a partitioned data file protects the database if immediate transaction recording is not essential.
An algorithm for optimized Boolean evaluation in information management systems
In cases where simple data validation techniques are inadequate and optimization policies relatively complex (e.g., in health and medical systems), a Boolean optimization algorithm can be used to report errors accurately and unambiguously. The algorithm is presented in the context of a data-validating software module that uses an LR(1)-parser. The algorithm's precision makes it of potential use for the retrieval of records that nearly satisfy a query.
A critque of the stage hypothesis: theory and empirical evidence
The stage hypothesis on the assimilation of computing technology provides one of the most popular models for describing and managing the growth of administrative information systems. Despite little formal evidence of its reliability or robustness, it has achieved a high level of acceptance among practitioners. We describe and summarize the findings of seven empirical studies conducted during the past six years that tested various hypotheses derived from this model. The accumulation of evidence from these studies casts considerable doubt on the validity of the stage hypothesis as an explanatory structure for the growth of computing in organizations.
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Online help systems: a conspectus
Users of computer systems are now accustomed to the convenience of online help systems and generally demand these amenities in the computers they buy. However, recent studies as to the efficacy of certain types of assistance for certain classes of users raise important questions for designers.
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