June 1988 - Vol. 31 No. 6
Features
Tablet: personal computer of the year 2000
A design represents a compromise between conflicting goals, and the design of the personal computer of the year 2000 is no exception. We seek something that will fit comfortably into people's lives while dramatically changing them. This may appear to be a contradiction that cannot be reconciled. But if the technology does not fit easily into the habits and lifestyles of its human users, it will be discarded by those it was meant to help. And if this new tool does not change the life of its owner, it is only because we have been too shortsighted to imagine the possibilities.
Our way out of this dilemma is to base the design upon something which is already integrated into everyone's life, to take a vital tool and give it more life. We have chosen to improve something that most people use everyday, the humble paper notebook.
We have all heard the computer revolution was supposed to eliminate paper from the workplace. Instead, it has lead to desktop publishing; now we can not only write papers but typeset them ourselves. Paper notebooks have many properties that make them particularly friendly. They are light and portable. No one thinks twice about taking a pad anywhere. They are easy and natural to use, as accessible to the toddler as to the octogenarian and as relevant to the artist as the engineer. They can be used to communicate with other people. They are the ideal medium for integrating text and graphics, and perfect for creative doodling. Moreover, notebooks are forgiving of mistakes, simply peel off the page and start anew.
It is natural to revise and edit written documents. There is something satisfying about crossing out an offending sentence from a written draft, a feeling that word processors have not captured. We aim for a computer that will provide all of these benefits and more.
Thus, the personal computer of the year 2000 will be a portable machine the size of a notebook. We will write and draw with a stylus on a screen which mimics a physical writing surface. Enhancing this with the powers of computation and communication, we create a tool that will improve the way we live and work.
This report provides a more concrete depiction of the machine we have in mind, namely TABLET.
Computer graphics tools for the study of minimal surfaces
Recent research indicates machine computation and mathematical theory have proceeded hand in hand and have proved to be of great benefit to one another.
Introduction to special section on software testing
The field of software testing spans mathematical theory, the art and practice of validation, and methodology of software development. To cover this range would require a textbook (or several texts), not a trio of articles. But the work presented in this special section is a kind of "test set." Each paper is a significant contribution within one of the three broad areas. The reader must now make the assessment that is critical to any review of test points: are they representative? My own answer is 'no'; these articles are provocative and revealing rather than routine summaries. And perhaps that is what software testing is all about: good tests are the ones that provide new insights, not the ones that cover well worn ground.
The evaluation of program-based software test data adequacy criteria
In earlier work, a preliminary set of axioms for software test data adequacy was introduced in order to formalize properties which should be satisfied by any good program-based adequacy criterion. Here, we extend this work by augmenting the set with additional axioms which substantially strengthen the set. In doing so, we rule out several types of unsuitable notions of adequacy.
The category-partition method for specifying and generating fuctional tests
A method for creating functional test suites has been developed in which a test engineer analyzes the system specification, writes a series of formal test specifications, and then uses a generator tool to produce test descriptions from which test scripts are written. The advantages of this method are that the tester can easily modify the test specification when necessary, and can control the complexity and number of the tests by annotating the tests specification with constraints.
The growth of software testing
We can trace the evolution of software test engineering by examining changes in the testing process model and the level of professionalism over the years. The current definition of a good software testing practice involves some preventive methodology.
Self-timing programs and the quantum scheduler
Using an internally generated program clock in conjunction with a quantum scheduler creates self-timing programs that are useful in building deterministic computer systems.
Model management and structured modeling: the role of an information resource dictionary system
Models have historically occupied an ambiguous position within organizations. Management acceptance of management science and operations research models for decision-making has lagged far behind technical advances in these areas. Structured modeling has emerged as a unifying approach to the modeling process with potential to reduce this ambiguity. Structured modeling is primarily oriented to the individual, however. A way of incorporating structured modeling into the organizational framework via existing information resource channels is discussed. A relational model is presented for an information resource dictionary system (IRDS). This IRDS model is then extended to accommodate representation of structured models. This extension of the IRDS can answer queries about structured modeling as well as model instances. The concept of an active IRDS is introduced and an example presented of how an active IRDS can be linked with an optimization algorithm. The conclusion is that the IRDS is a suitable vehicle for incorporating model management and structured modeling as part of an organization's information resource management environment.
Garbarge collection for Prolog based on WAM
The Warren abstract machine (WAM) has become a generally accepted standard Prolog implementation technique. Garbage collection is an important aspect in the implementation of any Prolog system. A synopsis of the WAM is presented and then marking and compaction algorithms are shown that take advantage of WAM's unique use of the data areas. Marking and compaction are performed on both the heap and the trail; both use pointer reversal techniques, which obviate the need for extra stack space. However, two bits for every pointer on the heap are reserved for the garbage collection algorithm. The algorithm can work on segments of the heap, which may lead to a significant reduction of the total garbage collection time. The time of the algorithms are linear in the size of the areas.
Efficient and portable combined random number generators
In this paper we present an efficient way to combine two or more Multiplicative Linear Congruential Generators (MLCGs) and propose several new generators. The individual MLCGs, making up the proposed combined generators, satisfy stringent theoretical criteria for the quality of the sequence they produce (based on the Spectral Test) and are easy to implement in a portable way. The proposed simple combination method is new and produces a generator whose period is the least common multiple of the individual periods. Each proposed generator has been submitted to a comprehensive battery of statistical tests. We also describe portable implementations, using 16-bit or 32-bit integer arithmetic. The proposed generators have most of the beneficial properties of MLCGs. For example, each generator can be split into many independent generators and it is easy to skip a long subsequence of numbers without doing the work of generating them all.
A rectangular dissection is a partition of a rectangular space R info n ≱ 1 disjoint rectangles {r1, r2, . . ., rn. Two classes of dissections that are of particular interest in floor-space design and very-large-scale integration (VLSI) space partitioning are called T-plans and T*-plans, where the T*-plans form a subclass of the T-plans. We consider here the subregion tree representation t(D) of a T*-plan D, which describes the successive partitioning operations by which the dissection D is derived. There are four types of partitioning operations in a T*-plan: (1) the horizontal partitioning; (2) the vertical partitioning; (3) the left-spiral partitioning; and (4) the right-spiral partitioning. We show that for a T*-plan the subregion representation and the wall representation are equivalent in the sense that one can be obtained from the other in a unique fashion. The importance of this equivalence property lies in that while the two representations allow different types of design constraints to be represented in a more natural way, these constraints may be converted to the same representation for a more efficient solution of the design problem.
Graphics and managerial decision making: research-based guidelines
Graphical charts are generally thought to be a superior reporting technique compared to more traditional tabular representations in organizational decision making. The experimental literature, however, demonstrates only partial support for this hypothesis. To identify the characteristics of the situations that have been shown to benefit from the use of graphics, existing studies are reviewed in terms of the type of task used, the format employed, and the user experience. The examination of the literature reveals a set of empirically based—though preliminary—guidelines as to when and how to use business graphics.
