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.     

Location,Localization, and Localizability

Location-aware technology spawns numerous unforeseen pervasive applications in a wide range of living,production, commence,and public services.This article provides an overview of the location,localization,and localizability issues of wireless ad-hoc and sensor networks.Making data geographically meaningful,location information is essential for many applications,and it deeply aids a number of network functions,such as network routing,topology control,coverage, boundary detection,clustering,etc.We investi...     

Motility,mixing, and multicellularity

A fundamental issue in evolutionary biology is the transition from unicellular to multicellular organisms, and the cellular differentiation that accompanies the increase in group size. Here we consider recent results on two types of “multicellular” systems, one produced by many unicellular organisms acting collectively, and another that is permanently multicellular. The former system is represented by groups of the bacterium Bacillus subtilis and the latter is represented by members of the colonial volvocalean green algae. In these flagellated organisms, the biology of chemotaxis, metabolism and cell–cell signaling is intimately connected to the physics of buoyancy, motility, diffusion, and mixing. Our results include the discovery in bacterial suspensions of intermittent episodes of disorder and collective coherence characterized by transient, recurring vortex streets and high-speed jets of cooperative swimming. These flow structures markedly enhance transport of passive tracers, and therefore likely have significant implications for intercellular communication. Experiments on the Volvocales reveal that the sterile flagellated somatic cells arrayed on the surface of Volvox colonies are not only important for allowing motion toward light (phototaxis), but also play a crucial role in driving fluid flows that transport dissolved molecular species. These flows, generated by the collective beating of flagella, confer a synergistic advantage with regard to transport of nutrients and chemical messengers. They allow these species to circumvent a nutrient acquisition bottleneck which would exist if transport were purely diffusive, and thereby evolve to larger multicellular individuals. In both cases, a higher level of organization, specialization and complexity counteract the higher costs inherent to larger groups.     

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?     

Budgets, Blood, and Turnips

Although the need for new systems (instead of constant maintenance of older systems) is often quite apparent to the MIS department, their advantages are not so readily realized by senior management -which sees only costs and risks instead of benefits. As a result, MIS managers must prove the costs and benefits of such projects. This column examines the difficulty of measuring the costs and benefits of four generations of systems -batch, online, DBMS based, and maintenance motivated - and explains why MIS managers should not only rewrite old systems but turn their attention toward the development of new and innovative systems.     

Goals,values, and reasoning

It is impossible to model human reasoning without taking into consideration the values and goals behind a decision. Although the problem of inference with values and goals has been discussed by a number of authors, many issues still stand in need of further development. The main purpose of this work is to discuss the issue of modeling of values and goals in reasoning and argumentation, hence the need for an analysis of existing definitions of values and goals, a discussion of relations between them, and the formulation of value- and goal-based mechanisms of reasoning.     

Similarity,topology, and uniformity

We generalize various notions of generalized metrics even further to one general concept comprising them all. For convenience, we turn around the ordering in the target domain of the generalized metrics so that we speak of similarity instead of distance. Starting from an extremely general situation without axioms, we examine which axioms or additional properties are needed to obtain useful results. For instance, we shall see that commutativity and associativity of the generalized version of addition occurring in the triangle inequality are not really needed, nor do we require a generalized version of subtraction.Each similarity space comes with its own domain of possible similarity values. Therefore, we consider non-expanding functions modulo some rescaling between different domains of similarity values. We show that non-expanding functions with locally varying rescaling functions correspond to topologically continuous functions, while non-expanding functions with a globally fixed rescaling generalize uniformly continuous functions.     

Work, Retirement, and Depression

This study investigates the relationship between depression and labor force participation by examining whether retirement induces depression or depression discourages labor force participation. The sample is drawn from newly available, nationally representative data of those 50–64 years old using the 2006 Korean Longitudinal Study of Aging. We model two possibly inter-related outcomes; depression and work. We first examine whether retirement influences depression, using the mandatory retirement provisions of the Korean labor force to identify a pathway to retirement that is not a consequence of depression. We then estimate the determinants of current work using instrumental variables for depression. We find that mandatory retirement is not associated with subsequent depression but find evidence that depression leads to reduced labor force participation, after using instrumental variables to predict the existence of depressive symptoms among respondents. We find strong evidence that depression leads to reduced labor force participation. Although retirees are often more depressed than workers, the causes that induce retirement, such as poor health, care-giving responsibilities, and inability to find a job, are also associated with depression.     

DRM, Complexity, and Correctness

Steve Bellovin looks at the complex code behind Microsoft Vista and its DRM mechanisms. Increased amounts of code add to insecurity, but the real danger with DRM is with increased interaction among different pieces of code. A lot of new mechanisms have been introduced; more seriously, a lot of new communications paths and dependencies have been introduced. Worst of all, these paths and mechanisms are solving a new problem, one with which the profession has very little experience. Did Microsoft get it right?     

Texture,contour, shape,and motion

Intrinsic magic calculation exploits constraints arising from physical and imaging processes to derive physical scene parameters from input images. After a brief review of a paradigmatic intrinsic image calculation we turn to a recent result in shape from texture and then to a new result that derives shape and motion from a sequence of patterned inputs. Experimental results are demonstrated for synthetic and natural images.     

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.     

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     

Past, Present, and Future

Thomas L. Friedman. the World Is Flat: A Brief History of the Twenty-First Century. N ew York: Farrar, Straus and Giroux, 2005, 488 pp.

Nicholas G. Carr. Does IT Matter? Information Technology and the Corrosion of Competitive Advantage. Boston: Harvard Business School Press, 2004, 193 pp.

John Hagel III and John Seely Brown. the Only Sustainable Edge: Why Business Strategy Depends on Productive Friction and Dynamic Specialization. Boston: Harvard Business School Press, 2005, 218 pp.

John Markoff. What the Dormouse Said. New York: Viking, 2005, 301 pp.     

Quantifiers, Anaphora, and Intensionality

The relationship between Lexical-Functional Grammar (LFG) functional structures (f-structures) for sentences and their semanticinterpretations can be formalized in linear logic in a way thatcorrectly explains the observed interactions between quantifier scopeambiguity, bound anaphora and intensionality.Our linear-logic formalization of the compositional properties ofquantifying expressions in natural language obviates the need forspecial mechanisms, such as Cooper storage, in representing thescoping possibilities of quantifying expressions. Instead, thesemantic contribution of a quantifier is recorded as a linear-logicformula whose use in a proof will establish the scope of thequantifier. Different proofs can lead to different scopes. In eachcomplete proof, the properties of linear logic ensure thatquantifiers are properly scoped.The interactions between quantified NPs and intensional verbs such asseek are also accounted for in this deductive setting. A singlespecification in linear logic of the argument requirements ofintensional verbs is sufficient to derive the correct readingpredictions for intensional-verb clauses both with nonquantified andwith quantified direct objects. In particular, both de dictoand de re readings are derived for quantified objects. Theeffects of type-raising or quantifying-in rules in other frameworksjust follow here as linear-logic theorems.While our approach resembles current categorial approaches inimportant ways (Moortgat, 1988, 1992a; Carpenter, 1993; Morrill, 1994)it differs from them in allowing the greater compositional flexibility ofcategorial semantics (van Benthem, 1991)while maintaining a precise connection to syntax. As a result, we areable to provide derivations for certain readings of sentences withintensional verbs and complex direct objects whose derivation inpurely categorial accounts of the syntax-semantics interface appearsto require otherwise unnecessary semantic decompositions of lexicalentries.     

Agents, grids, and middleware

Agents, grids, and middleware are more closely related. We develop software architecture for two software projects: one involves infrastructure for distributed, pervasive computing; the other involves partitioning huge data sets across data grids consisting of thousands of PCs. On the surface, these projects seem very different, but there are similarities and lessons we can learn from comparing them that have implications for agents, grids, Web services, pervasive computing, and middleware.     

Plans, lies, and videotape

The authors pose the question: why are smart, skilled, responsible, experienced software people so often mixed up about commitments? They make a list of reasons for why otherwise capable, well intentioned people appear not to meet their commitments: no commitment in the first place; conditional commitments, with conditions unmet; commitment to work toward a goal, rather than achieve it; different impressions of the true commitment; commitments made under duress; commitment made in error; commitments not worth the effort to fulfill; terms of commitment changed midstream     

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.