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.

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.     

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.     

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.     

Children, robotics, and education

Popular interest in robotics has increased astonishingly in the last few years. Robotics is seen by many as offering major new benefits in education at all levels. Before rushing to exploit this popularity, educators should ask serious questions about the universality and longevity of the robotics phenomenon. Is it a fashion? To be useful, the energy released by robotics must be sustained and universal, and the means of exploiting it must be systematic. Universities define their own robotics curriculum, but most schools lack both the resources and the freedom to do this, and must work with a national curriculum. If it can be shown that robotics has sustained potential in education, it seems inevitable that new ways need to be found to integrate it into the school curriculum.     

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.     

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.     

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.     

Complexity,convexity, and unimodality

A class of polygons termedunimodal is introduced. LetP = P₁,p ₂,...,p _n be a simplen-vertex polygon. Given a fixed vertex or edge, several definitions of the distance between the fixed vertex or edge and any other vertex or edge are considered. For a fixed vertex (edge), a distance measure defines a distance function as the remaining vertices (edges) are traversed in order. If for every vertex (edge) ofP a specified distance function is unimodal thenP is a unimodal polygon in the corresponding sense. Relationships between unimodal polygons, in several senses, andconvex polygons are established. Several properties are derived for unimodal polygons when the distance measure is the euclidean distance between vertices of the polygons. These properties lead to very simple 0(n) algorithms for solving a variety of problems that occur in computational geometry and pattern recognition. Furthermore, these algorithms establish that convexity is not the key factor in obtaining linear-time-complexity for solving these problems. The paper closes with several open questions in this area.     

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.     

Deduction, Strategies, and Rewriting

Automated deduction methods should be specified not procedurally, but declaratively, as inference systems which are proved correct regardless of implementation details. Then, different algorithms to implement a given inference system should be specified as strategies to apply the inference rules. The inference rules themselves can be naturally specified as (possibly conditional) rewrite rules. Using a high-performance rewriting language implementation and a strategy language to guide rewriting computations, we can obtain in a modular way implementations of both the inference rules of automated deduction procedures and of algorithms controling their application. This paper presents the design of a strategy language for the Maude rewriting language that supports this modular decomposition: inference systems are specified in system modules, and strategies in strategy modules. We give a set-theoretic semantics for this strategy language, present its different combinators, illustrate its main ideas with several examples, and describe both a reflective prototype in Maude and an ongoing C++ implementation.     

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.     

Threat assessment,sense making,and critical decision-making in police,military, ambulance,and fire services

Cognition, Technology & Work - Military and emergency response remain inherently dangerous occupations that require the ability to accurately assess threats and make critical decisions under...