Pointcuts, advice, refinements, and collaborations: similarities, differences, and synergies

Aspect-oriented programming (AOP) is a novel programming paradigm that aims at modularizing complex software. It embraces several mechanisms including (1) pointcuts and advice as well as (2) refinements and collaborations. Though all these mechanisms deal with crosscutting concerns, i.e., a special class of design and implementation problems that challenge traditional programming paradigms, they do so in different ways. In this article we explore their relationship and their impact on modularity, which is an important prerequisite for reliable and maintainable software. Our exploration helps researchers and practitioners to understand their differences and exposes which mechanism is best used for which problem.     

Household technology adoption,use, and impacts: Past,present, and future

Since the 1980s, researchers have been studying the phenomenon associated with technology being diffused to the household. In this paper, three themes in that stream of research, specifically adoption, use, and impacts, are explored. Key studies from prior research within each theme are discussed and directions for future research are offered. The directions for future research range from investigating adoption issues associated with the digital divide to understanding the impacts of new technology and social networking sites on individuals and families. The evolving nature of the technology continues to offer interesting research directions and challenges, with the study of unintended consequences of technology use presenting, perhaps, the greatest opportunities.

Information and communication activity,its essence,structure, and types

The problem of defining the primary forms of information objects is considered. It is proposed to include messages, algorithms, and models in this class.     

Electronic Markets, Hierarchies, Hubs, and Intermediaries

The impact of information technologies on organizations is difficult to predict, although critical for developing comprehensive organizational strategies. Much of the difficulty is traceable to the treatment of all information technologies as a single factor, when in fact different technologies may have drastically different impacts on the organization. Specifically, the distinction between two general classes of technologies, communication and information processing technologies, is studied. An analytical model is developed to show that these two classes of technologies have exactly the opposite impacts on the organization. Moreover, the impact also depends on the organization, and its existing structure. Communication intensive and processing intensive organizational structures are distinguished and they are shown to be impacted differently by information technologies. An analytical framework is developed to show a continuum of organizational structures, depending on their relative communication and processing intensity, and the effect of various technologies is shown to be to move the organization along that continuum. Communication and information processing technologies are shown to move the organization in opposing directions. Finally, the analytical framework is shown to be robust and valid under a wide variety of conditions, covering most real life organizations.     

Logic,topology, and integration

The central notion presented is that of closeness of (or difference between) two theories. In the first part, we give intuitive arguments in favor of considering topologies on the set of theories, continuous logics, and the average difference between two logics (i.e., the integral of their difference). We argue for the importance of the difference between theories in a wide range of applications and problems. In the second part, we give some basic definitions and results for one such type of topology. In particular, separation properties and compactness are discussed and examples given. The techniques employed for constructing the topology are also used for defining a -algebra of measurable sets on the set of theories, leading to the usual definition of the Lebesgue integral and a precise definition of the average difference of two logics.     

Recipes,Algorithms, and Programs

In the technical literature of computer science, the concept of an effective procedure is closely associated with the notion of an instruction that precisely specifies an action. Turing machine instructions are held up as providing paragons of instructions that "precisely describe" or "well define" the actions they prescribe. Numerical algorithms and computer programs are judged effective just insofar as they are thought to be translatable into Turing machine programs. Nontechnical procedures (e.g., recipes, methods) are summarily dismissed as ineffective on the grounds that their instructions lack the requisite precision. But despite the pivotal role played by the notion of a precisely specified instruction in classifying procedures as effective and ineffective, little attention has been paid to the manner in which instructions "precisely specify" the actions they prescribe. It is the purpose of this paper to remedy this defect. The results are startling. The reputed exemplary precision of Turing machine instructions turns out to be a myth. Indeed, the most precise specifications of action are provided not by the procedures of theoretical computer science and mathematics (algorithms) but rather by the nontechnical procedures of everyday life. I close with a discussion of some of the rumifications of these conclusions for understanding and designing concrete computers and their programming languages.     

Petri nets, algebras, morphisms, and compositionality

It is shown how a category of Petri nets can be viewed as a subcategory of two sorted algebras over multisets. This casts Petri nets in a familiar framework and provides a useful idea of morphism on nets different from the conventional definition—the morphisms here respect the behaviour of nets. The categorical constructions which result provide a useful way to synthesise nets and reason about nets in terms of their components; for example, various forms of parallel composition of Petri nets arise naturally from the product in the category. This abstract setting makes plain a useful functor from the category of Petri nets to a category of spaces of invariants and provides insight into the generalisations of the basic definition of Petri nets—for instance, the coloured and higher level nets of Kurt Jensen arise through a simple modification of the sorts of the algebras underlying nets. Further, it provides a smooth formal relation with other models of concurrency such as Milner's calculus of communicating systems (CCS) and Hoare's communicating sequential processes (CSP), though this is only indicated in this paper.     

Mandalas,screws, pears,and Klein bottles

The goal of this article is to present an informal introduction and tutorial on the production of aesthetically pleasing solid models. The article is intended for the nonmathematical reader interested in computer art. Simple generating formulas and recipes are included.     

Reviews, Walkthroughs, and Inspections

Formal technical reviews supply the quality measurement to the ``cost effectiveness' equation in a project management system. There are several unique formal technical review procedures, each applicable to particular types of technical material and to the particular mix of the Review Committee. All formal technical reviews produce reports on the overall quality for project management, and specific technical information for the producers. These reports also serve as an historic account of the systems development process. Historic origins and future trends of formal and informal technical reviews are discussed.     

Contracts,Games, and Refinement

We consider the notion of a contract that governs the behavior of a collection of agents. In particular, we study the question of whether a group among these agents can achieve a given goal by following the contract. We show that this can be reduced to studying the existence of winning strategies in a two-person game. A notion of correctness and refinement is introduced for contracts and contracts are shown to form a lattice and a monoid with respect to the refinement ordering. We define a weakest precondition semantics for contracts that permits us to compute the initial states from which a group of agents has a winning strategy to reach their goal. This semantics generalizes the traditional predicate transformer semantics for program statements to contracts and games. Ordinary programs and interactive programs are special kinds of contracts.     

Cyberculture,symbiosis, and syncretism

The impact of Cyberculture, of digital devices on young people as extensions of the body, can be seen in terms of the decreasing structuring of thoughts and information, increasing impulsivity in perception and action, and the development of more primitive defense mechanisms. These adverse impacts result in the feeling of isolation and devaluation, frustration of present and uncertainty of the future, exteriorization and floating identities, mimetic and adhesive identifications, less cohesion of the self, and decreasing tolerance of the other. This paper focuses on the following themes: Symbiosis versus syncretism: The affirmations of symbiosis. The dilutions of syncretism. Synopsis: Too much syncretism, too little symbiosis. Lack of a deeper co-construction of knowledge, more lasting, and sustainable. Lack of increased more independent personal cognitive deepening. Lack of ability to be alone. Causality and free will: Symbiotic versus syncretic causality. Conclusions: Cyber-selfs—either distributed or not at all?     

Jobs, trades, skills, and the profession

Is the reputed shortage of IT skills a political scam or is the computing profession itself at fault? The author considers IT professional responsibility and training issues.     

Computers,Computation, and Problems

Abstract

The automatic recognition of targets involving significant intraclass variations is a challenging problem if the solution is constrained by practical implementability considerations. In the case of Gaussian intraclass variations the exact solution is implementable but in a somewhat complex way. The exact solutions of non-Gaussian cases are, with few exceptions, not implementable. We have developed a systematic approximation procedure for obtaining implementable solutions for these cases. Analysis of the approximation errors is given.     

Invariants,composition, and substitution

In the literature the notion of asystem invariant has been formalized in two different ways, differing in the treatment of unreachable transitions. We call the more general notion, which ignores unreachable transitions,invariant sets of a system, the more restricted notion, which considers unreachable transitions,inductive sets of a system.It turns out that even if we are only interested in invariant sets of a system, inductive sets play an important rôle for proving invariant sets of system in a compositional way. This paper shows the interplay of both kinds of invariants; particularly, we show that inductive sets arefully abstract with respect to invariant sets.One essential difference between invariant and inductive sets is that thesubstitution rule is only valid for invariant sets, and thecomposition rule is only valid for inductive sets. Sometimes it seems desirable to have a notion of invariants for which both rules are valid. We show that every notion of an invariant enjoying both rules is very restrictive.Supported by the DFG SFB 342, TP A3: SEMAFOR and the ESPRIT Basic Research WG 6067 Caliban     

Photos,time, navigation,visualization, recommendation and interactive TV: issues and contributions

In this editorial we first present the ACM Symposium on Applied Computing (SAC) and its Multimedia and Visualization (MMV) track. Next, we introduce the papers which were selected from the MMV track at the 2009 edition of SAC to present novel results in extended versions in this special issue.     

Intuition,Computation, and Information

Bynum (Putting information first: Luciano Floridi and the philosophy of information. NY: Wiley-Blackwell, 2010) identifies Floridi’s focus in the philosophy of information (PI) on entities both as data structures and as information objects. One suggestion for examining the association between the former and the latter stems from Floridi’s Herbert A. Simon Lecture in Computing and Philosophy given at Carnegie Mellon University in 2001, open problems in the PI: the transduction or transception, and how we gain knowledge about the world as a complex, living, information environment. This paper addresses PI across a model of interoperating levels: perception (P)—intuition (N)—computation (C)—information (I), as factored by cognitive continuity (1), temporality (2), and constitution (3). How might we begin to characterize our experience of an abstract information object across such a matrix? Chudnoff’s rationalist distinctions between perception and intuition serve as a first rung of the ladder. Turing’s brief references to the utility of intuition, in an allied, rationalist-Cartesian sense, provide the next step up to computation. Floridi provides the final link from computation to information.     

Work-arounds, make-work, and kludges

Paradigms are often defined partly in terms of what they are not, or in terms of what they are reacting against. The paradigm of human-centered computing is no exception. We discuss about a user-hostile system. We decided that the terms kludge and work-around, and also the related concept of make-work, has yet to be clearly defined for the intelligent systems community. Human-centered systems are different from user-hostile systems as well as from systems based on a designer-centered approach. We try to clarify the senses of these three terms and suggest ways we might study work-around, make-work, and kludges as an integral part of human-computer systems-rather than as embarrassing necessities that are best swept under the computing research rug.     

Worlds,Events, and Inertia

The semantics of progressive sentences presents a challenge to linguists and philosophers alike. According to a widely accepted view, the truth-conditions of progressive sentences rely essentially on a notion of inertia. Dowty (Word meaning and Montague grammar: the semantics of verbs and times in generative grammar and in Montague’s PTQ, D. Reidel Publishing Company, Dordrecht, 1979) suggested inertia worlds to implement this “inertia idea” in a formal semantic theory of the progressive. The main thesis of the paper is that the notion of inertia went through a subtle, but crucial change when worlds were replaced by events in Landman (Nat Lang Semant 1:1–32, 1992) and Portner (Language 74(4):760–787, 1998), and that this new, event-related concept of inertia results in a possibility-based theory of the progressive. An important case in point in the paper is a proof that, despite its surface structure, the theory presented in Portner (1998) does not implement the notion of inertia in Dowty (1979); rather, it belongs together with Dowty’s earlier, 1977 theory according to which the progressive is a possibility operator.