From the Publisher:
Written by the author of the best-selling HyperText & HyperMedia, this book provides an excellent guide to the methods of usability engineering. Special features: emphasizes cost-effective methods that will help developers improve their user interfaces immediately, shows you how to avoid the four most frequently listed reasons for delay in software projects, provides step-by-step information about which methods to use at various stages during the development life cycle, and offers information on the unique issues relating to informational usability. You do not need to have previous knowledge of usability to implement the methods provided, yet all of the latest research is covered.

Usability Engineering

Ptolemy is an environment for simulation and prototyping of heterogeneous systems. It uses modern object-oriented software technology (C++) to model each subsystem in a natural and efficient manner, and to integrate these subsystems into a whole. Ptolemy encompasses practically all aspects of designing signal processing and communications systems, ranging from algorithms and communication strategies, simulation, hardware and software design, parallel computing, and generating real-time prototypes. To accommodate this breadth, Ptoloemy must support a plethora of widely differing design styles. The core of Ptolemy is a set of object-oriented class definitions that makes a few assumptions about the system to be modeled; rather, standard interfaces are provided for generic objects and more specialized, application-specific objects are derived from these. A basic abstraction in Ptolemy is the Domain, which realizes a computational model appropriate for a particular type of subsystem. Current examples of domains include synchronous and dynamic dataflow, discrete-event, and others appropriate for control software and embedded microcontrollers. Domains can be mixed as appropriate to realize and overall system simulation. Some current applications of Ptolemy include networking and transport, call-processing and signaling software, embedded microcontrollers, signal processing (including implementation in real-time), scheduling of parallel digital signal processors, board-level hardware timing simulation, and combinations of these.

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Ptolemy: a framework for simulating and prototyping heterogeneous systems

Awareness and use of agile methods has grown rapidly among the information systems development (ISD) community in recent years. Like most previous methods, the development and promotion of these methods have been almost entirely driven by practitioners and consultants, with little participation from the research community during the early stages of evolution. While these methods are now the focus of more and more research efforts, most studies are still based on XP, Scrum, and other industry-driven foundations, with little or no conceptual studies of ISD agility in existence. As a result, this study proposes that there are a number of significant conceptual shortcomings with agile methods and the associated literature in its current state, including a lack of clarity, theoretical glue, parsimony, limited applicability, and naivety regarding the evolution of the concept of agility in fields outside systems development. Furthermore, this has significant implications for practitioners, rendering agile method comparison and many other activities very difficult, especially in instances such as distributed development and large teams that are not conducive to many of the commercial agile methods. This study develops a definition and formative taxonomy of agility in an ISD context, based on a structured literature review of agility across a number of disciplines, including manufacturing and management where the concept originated, matured, and has been applied and tested thoroughly over time. The application of the texonomy in practice is then demonstrated through a series of thought trials conducted in a large multinational organization. The intention is that the definition and taxonomy can then be used as a starting point to study ISD method agility regardless of whether the method is XP or Scrum, agile or traditional, complete or fragmented, out-of-the-box or in-house, used as is or tailored to suit the project context.

https://ulir.ul.ie/bitstream/handle/10344/574/L%201.pdf;sequence=2

Agility from First Principles: Reconstructing the Concept of Agility in Information Systems Development

Hypertext development should benefit from a systematic, structured development, especially in the case of large and complex applications. A structured approach to hypertext development suggests the notion of authoring-in-the-large. Authoring-in-the-large allows the description of overall classes of information elements and navigational structures of complex applications without much concern with implementation details, and in a system-independent manner. The paper presents HDM (Hypertext Design Model), a first step towards defining a general purpose model for authoring-in-the-large. Some of the most innovative features of HDM are: the notion of perspective; the identification of different categories of links (structural links, application links, and perspective links) with different representational roles; the distinction between hyperbase and access structures; and the possibility of easily integrating the structure of a hypertext application with its browsing semantics. HDM can be used in different manners: as a modeling device or as an implementation device. As a modeling device, it supports producing high level specifications of existing or to-be-developed applications. As an implementation device, it is the basis for designing tools that directly support application development. One of the central advantages of HDM in the design and practical construction of hypertext applications is that the definition of a significant number of links can be derived automatically from a conceptual-design level description. Examples of usage of HDM are also included.

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HDM—a model-based approach to hypertext application design

The authors build upon research by E. A. Lee (1991) concerning the token flow model, an analytical model for the behavior of dataflow graphs with data-dependent control flow, by analyzing the properties of cycles of the schedule: sequences of actor executions that return the graph to its initial state. Necessary and sufficient conditions are given for the existence of a bounded cyclic schedule as well as sufficient conditions for execution of the graph in bounded memory. The techniques presented apply to a more general class of dataflow graphs than previous methods. >

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Scheduling dynamic dataflow graphs with bounded memory using the token flow model

We present a formal definition of the Trellis model of hypertext and describe an authoring and browsing prototype called aTrellis that is based on the model. The Trellis model not only represents the relationships that tie individual pieces of information together into a document (i.e., the adjacencies), but specifies the browsing semantics to be associated with the hypertext as well (i.e., the manner in which the information is to be visited and presented). The model is based on Petri nets, and is a generalization of existing directed graph-based forms of hypertext. The Petri net basis permits more powerful specification of what is to be displayed when a hypertext is browsed and permits application of previously developed Petri net analysis techniques to verify properties of the hypertext. A number of useful hypertext constructs, easily described in the Trellis model, are presented. These include the synchronization of simultaneous traversals of separate paths through a hypertext, the incorporation of access controls into a hypertext (i.e., specifying nodes that can be proven to be accessible only to certain classes of browsers), and construction of multiple specialized (tailored) versions from a single hypertext.

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Petri-net-based hypertext: document structure with browsing semantics

Pair programming is one of the twelve practices of Extreme Programming (XP). Pair programming is usually performed by programmers that are collocated - working in front of the same monitor. But the inevitability of distributed development of software gives rise to important questions: How effective is pair programming if the pairs are not physically next to each other? What if the programmers are geographically distributed? An experiment was conducted at North Carolina State University to compare different working arrangements of student teams developing object-oriented software. Teams were both collocated and in distributed environments; some teams practiced pair programming while others did not. In particular, we compared the software developed by virtual teams using distributed pair programming against collocated teams using pair programming and against virtual teams that did not employ distributed pair programming. The results of the experiment indicate that it is feasible to develop software using distributed pair programming, and that the resulting software is comparable to software developed in collocated or virtual teams (without pair programming) in productivity and quality.

Exploring the Efficacy of Distributed Pair Programming

We present a view of hyperdocuments in which each document encodes its own browsing semantics in its links. This requires a mental shift in how a hyperdocument is thought of abstractly. Instead of treating the links of a document as defining a static directed graph, they are thought of as defining an abstract program, termed the links-automaton of the document. A branching temporal logic notation, termed HTL*, is introduced for specifying properties a document should exhibit during browsing. An automated program verification technique called model checking is used to verify that browsing specifications in a subset of HTL* are met by the behavior defined in the links-automation. We illustrate the generality of these techniques by applying them first to several Trellis documents and then to a Hyperties document.

Hyperdocuments as automata: verification of trace-based browsing properties by model checking

A technique is described for adapting the apparent structure of a hypertext to the behavior and preferences exhibited by its users while browsing. Examples are given an implementation of this technique using the timing mechanism in Trellis. In the technique, event durations in a document are altered without actually changing the links in the underlying Petri net. The two extrema of instantaneous events and infinite delays can be used to create apparent node and link deletions and additions, as well as to insert new tokens (loci of activity) into a document. Adaptation of these times is accomplished using a simple data state in which the event timings (and other document properties) are variables, called attributes. As a reader traverses hypertext links, author-supplied aulzptation agents are invoked to collect information and possibly change the values of the attributes. Agents encapsulate and effect the criteria for deciding when, and specifically how, a structure should be adapted. Several practical examples illustrate the conclusion of this repofi sophisticated alterations do not require a complicated adaptation mechanism, that changing document constants into document variables provides flexibility to this mechanism, and that using a limited simple mechanism is the only hope for retaining analysis of the static and dynamic net properties.

Dynamic adaptation of hypertext structure

Pair programming is a practice in which two programmers work together at one computer, collaborating on the same design, algorithm, code or test. Previous studies have shown that pair programmers produce higher quality code in essentially the same amount of time as solo programmers. Additional benefits include increased job satisfaction, improved team communication, and efficient tacit knowledge sharing. However, it may not always be possible for all team members to be collocated due to the rise in teleworking and geographically distributed teams. This paper analyzes the results of two distributed pair programming case studies done at UNC Chapel Hill and at NC State University. Participants used readily available off-the-shelf applications for collaborative software development. The results indicate that software development collaboratively “over the wire” is feasible, effective, and pleasant for the participants; distributed development is better done as synchronous pairs than as individuals who integrate; and distributed pairs maintain many of the advantages of collocated pairs.

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P. David Stotts

Papers

Petri-net-based hypertext: document structure with browsing semantics

Exploring the Efficacy of Distributed Pair Programming

Hyperdocuments as automata: verification of trace-based browsing properties by model checking

Dynamic adaptation of hypertext structure

Virtual teaming: Experiments and experiences with distributed pair programming