The Java Management Extensions (JMX): Is Your Cluster Ready for Evolution?

The arrival of commodity hardware configurations with performance rivaling that offered by RISC workstations is resulting in important advances in the state of the art of building and running very large scalable clusters at “mass market” pricing levels. However, cluster middleware layers are still considered as static infrastructures which are not ready for evolution. In this paper, we claim that middleware layers based on both agent and Java technologies offer new opportunities to support clusters where services can be dynamically added, removed, and reconfigured. To support this claim, we present the Java management extensions, a new Java agent-based technology, and its application to implement two disjoint cluster management middleware services (a remote reboot service and a distributed infrastructure for collecting Log events) which share a unique agent-based infrastructure.     

Is prototyping counterproductive?

Fourth-generation languages are not as simple to use as it may seem; as they can result in expensive machine utilization and inefficient use of disc space, disc I/O, memory and machine instructions.     

Is Submodularity Testable?

We initiate the study of property testing of submodularity on the boolean hypercube. Submodular functions come up in a variety of applications in combinatorial optimization. For a vast range of algorithms, the existence of an oracle to a submodular function is assumed. But how does one check if this oracle indeed represents a submodular function? Consider a function f:{0,1} ⁿ →?. The distance to submodularity is the minimum fraction of values of f that need to be modified to make f submodular. If this distance is more than ?>0, then we say that f is ?-far from being submodular. The aim is to have an efficient procedure that, given input f that is ?-far from being submodular, certifies that f is not submodular. We analyze a natural tester for this problem, and prove that it runs in subexponential time. This gives the first non-trivial tester for submodularity. On the other hand, we prove an interesting lower bound (that is, unfortunately, quite far from the upper bound) suggesting that this tester cannot be efficient in terms of ?. This involves non-trivial examples of functions which are far from submodular and yet do not exhibit too many local violations. We also provide some constructions indicating the difficulty in designing a tester for submodularity. We construct a partial function defined on exponentially many points that cannot be extended to a submodular function, but any strict subset of these values can be extended to a submodular function.     

Is Anybody Home?

At the recent consumer electronics show CES the big story was about how all the devices we'll be buying in the very near future will be Internet-capable. We should think about the broader notion of an ecology of connected devices: why this notion didn't work in the past, what it'll take to make it work this time, and what issues we, as designers of this ecology, should be thinking about as we move toward the future.     

Hello? Is Anybody Out There?

Well, here we are in the Year 2000, at least by one calendar — but we won’t go through that again. So, has the Y2K bug bitten you? I know it’s the last thing you probably want to hear right now. A combination of New Year’s celebrating and Y2K is enough to give anyone enough migraines to last until the next century.     

Is codasyl relevant today?

The history of Codasyl DBMS efforts is traced from actual Codasyl documents, and tends to suggest that today the Codasyl DBMS is no longer appropriate for modern needs. Further, an analysis of why and how this has happened in spite of well-intentioned Codasyl members is presented. Finally, a suggestion of ways in which Codasyl might be more effective in the future is offered.     

What Is Conceptual Glue?

Conceptual structures are commonly likened to scientific theories, yet the content and motivation of the theory analogy are rarely discussed. Gregory Murphy and Douglas Medin's The Role of Theories in Conceptual Coherence is a notable exception and has become an authoritative exposition of the utility of the theory analogy. For Murphy and Medin, the theory analogy solves what they call the problem of conceptual coherence or the problem of conceptual glue. I argue that they conflate a number of issues under these rubrics and that in each case either the problem to be solved isn't subject to a general solution or the theory analogy is of little use. The issues I consider are: (1) what makes a concept efficient, useful, and informative, (2) what makes a concept refer to what it does, (3) what makes a set of objects form a single category, and (4) what makes concepts combine in one way rather than another.     

Is a GigaLIP Fast Enough?

The capability of large, data-intensive expert systems is determined not only by the cleverness and expertise of their knowledge manipulation algorithms and methods but also by the fundamental speeds of the computer systems upon which they are implemented. To date, logical inferences per second (LIPS) is used as the power metric of the knowledge processing capacity of an expert system implementation. We show why this simplistic metric is misleading. We relate the power metrics for conventional computer systems to LIPS and demonstrate wide discrepancies. We review the power of today's largest conventional mainframes, such as the IBM 3090/400 and the Cray Research Cray-2 and forecast the expected power of mainframes and specialized processors in the coming decade.     

Is the Church-Turing thesis true?

The Church-Turing thesis makes a bold claim about the theoretical limits to computation. It is based upon independent analyses of the general notion of an effective procedure proposed by Alan Turing and Alonzo Church in the 1930's. As originally construed, the thesis applied only to the number theoretic functions; it amounted to the claim that there were no number theoretic functions which couldn't be computed by a Turing machine but could be computed by means of some other kind of effective procedure. Since that time, however, other interpretations of the thesis have appeared in the literature. In this paper I identify three domains of application which have been claimed for the thesis: (1) the number theoretic functions; (2) all functions; (3) mental and/or physical phenomena. Subsequently, I provide an analysis of our intuitive concept of a procedure which, unlike Turing's, is based upon ordinary, everyday procedures such as recipes, directions and methods; I call them mundane procedures. I argue that mundane procedures can be said to be effective in the same sense in which Turing machine procedures can be said to be effective. I also argue that mundane procedures differ from Turing machine procedures in a fundamental way, viz., the former, but not the latter, generate causal processes. I apply my analysis to all three of the above mentioned interpretations of the Church-Turing thesis, arguing that the thesis is (i) clearly false under interpretation (3), (ii) false in at least some possible worlds (perhaps even in the actual world) under interpretation (2), and (iii) very much open to question under interpretation (1).     

Where Is Computing Driving Cars?

Cars offer an excellent example of ubiquitous computing, and a technological revolution is currently underway that will eventually see in-vehicle computers empowered with increasingly complex sections of the driving task. In this article, we critically review the effect of ubiquitous computing in cars with reference to the psychology of the driver and present a survey of automotive researchers drawn from five major carmakers. The results illustrate the role of the computer in vehicles over the short, medium, and long term. Systems that are likely to be fitted into vehicles in the next 5 years include sophisticated electronic architectures and greater penetration of navigation and telematics systems. In the next 5 to 15 years drive by wire and collision sensing are anticipated. In the long term, 15 years and beyond, advanced driver-assistance systems will increasingly automate the driving task, and in-car personal computers and Internet will be commonplace. We conclude that the increased complexity and prominence of computing in cars requires further investigation of the needs, abilities, and limitations of the driver if the aims of safety, efficiency, and enjoyment, as well as greater ubiquity, are to be realized.     

Is Cybersecurity a Public Good?

Minds and Machines -     

Is the Hubble Constant Scale-Dependent?

An exact determination of the Hubble constant remains one of key problems in cosmology for almost a century. However, its modern values derived by various methods still disagree from each other by almost 10%, larger values being obtained by measurements at relatively small distances (e.g., by Cepheid stars as standard candles), while smaller values are characteristic of the methods associated with huge spatial scales (e.g., from the analysis of cosmic microwave background fluctuations). A reasonable way to resolve this puzzle is to assume that the Hubble constant is inherently scale-dependent. This idea seems to be particularly attractive in the light of the latest observational results on the early-type galaxies, where dark matter halos are almost absent. Therefore, an average contribution of the irregularly distributed dark matter to the rate of the cosmological expansion should be substantially different at various spatial scales. As follows from rough estimates, the corresponding variation of the Hubble constant can be about 10% and even more, which well explains the spread in its values obtained by different methods.     

Is cloned code really stable?

Clone has emerged as a controversial term in software engineering research and practice. The impact of clones is of great importance from software maintenance perspectives. Stability is a well investigated term in assessing the impacts of clones on software maintenance. If code clones appear to exhibit a higher instability (i.e., higher change-proneness) than non-cloned code, then we can expect that code clones require higher maintenance effort and cost than non-cloned code. A number of studies have been done on the comparative stability of cloned and non-cloned code. However, these studies could not come to a consensus. While some studies show that code clones are more stable than non-cloned code, the other studies provide empirical evidence of higher instability of code clones. The possible reasons behind these contradictory findings are that different studies investigated different aspects of stability using different clone detection tools on different subject systems using different experimental setups. Also, the subject systems were not of wide varieties. Emphasizing these issues (with several others mentioned in the motivation) we have conducted a comprehensive empirical study where we have - (i) implemented and investigated seven existing methodologies that explored different aspects of stability, (ii) used two clone detection tools (NiCad and CCFinderX) to implement each of these seven methodologies, and (iii) investigated the stability of three types (Type-1, Type-2, Type-3) of clones. Our investigation on 12 diverse subject systems covering three programming languages (Java, C, C#) with a list of 8 stability assessment metrics suggest that (i) cloned code is often more unstable (change-prone) than non-cloned code in the maintenance phase, (ii) both Type 1 and Type 3 clones appear to exhibit higher instability than Type 2 clones, (iii) clones in Java and C programming languages are more change-prone than the clones in C#, and (iv) changes to the clones in procedural programming languages seem to be more dispersed than the changes to the clones in object oriented languages. We also systematically replicated the original studies with their original settings and found mostly equivalent results as of the original studies. We believe that our findings are important for prioritizing code clones from management perspectives.     

How Strong Is Strong Regularity?

We compare the notions of regularity and strong regularity of interval matrices. For an n × n interval matrix A we construct 2ⁿ open convex cones, all of them lying in the interior of the nonnegative orthant. It is shown that regularity of A is characterized by nonemptiness of all these cones, whereas strong regularity is characterized by nonemptiness of their intersection.