1,721,076 research outputs found
Extracting the power of dependent types
No full textMost existing programming languages provide little support to formally state and prove properties about programs. Adding such capabilities is far from trivial, as it requires significant re-engineering of the existing compilers and tools. This paper proposes a novel technique to write correct-by-construction programs in languages without built-in verification capabilities, while maintaining the ability to use existing tools. This is achieved in three steps. Firstly, we give a shallow embedding of the language (or a subset) into a dependently typed language. Secondly, we write a program in that embedding, and we use dependent types to guarantee correctness properties of interest within the embedding. Thirdly, we extract a program written in the original language, so it can be used with existing compilers and tools. Our main insight is that it is possible to express all three steps in a single language that supports both dependent types and reflection. Essentially, this allows us to express a program, its formal properties, and a compiler for it hand-in-hand, offering a lot of flexibility to programmers. We demonstrate this three-step approach by embedding a subset of the PostScript language in Agda, and illustrating it with several short examples. Thus we use the power of reflection to bring the benefits of dependent types to languages that had to go without them so far. </p
Software Tools for Separating Distribution Concerns
No full textWith the advent of the Internet, distributed programming has become a necessity for the majority of application domains. Nevertheless, programming distributed systems remains a delicate and complex task. This dissertation explores separating distribution concerns,
the process of transforming a centralized monolithic program into a distributed one. This research develops algorithms, techniques, and tools for separating distribution concerns
and evaluates the applicability of the developed artifacts by identifying the distribution
concerns that they separate and the common architectural characteristics of the centralized programs that they transform successfully. The thesis of this research is that software tools working with standard mainstream languages, systems software, and virtual machines can effectively and efficiently separate distribution concerns from application logic for object-oriented programs that use multiple distinct sets of resources. Among the specific technical contributions of this dissertation are (1) a general algorithm for call-by-copy-restore semantics in remote procedure calls for linked data structures, (2) an analysis heuristic that determines which application objects get passed to which parts of native (i.e., platform-specific) code in the language runtime system for platform-independent binary code applications, (3) a technique for injecting code in such applications that will convert objects to the right representation so that they can be accessed correctly inside both application
and native code, (4) an approach to maintaining the Java centralized concurrency and synchronization semantics over remote procedure calls efficiently, and (5) an approach to enabling the execution of legacy Java code remotely from a web browser.
The technical contributions of this dissertation have been realized in three software tools for separating distribution concerns: NRMI, middleware with copy-restore semantics; GOTECH, a program generator for distribution; and J-Orchestra, an automatic partitioning system. This dissertation presents several case studies of successfully applying the developed
tools to third-party programs.Ph.D
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Delta-based Verification of Software Product Families
Full text linkThe quest for feature- and family-oriented deductive verification of software product lines resulted in several proposals. In this paper we look at delta-oriented modeling of product lines and combine two new ideas: first, we extend Hähnle & Schaefer’s delta-oriented version of Liskov’s substitution principle for behavioral subtyping to work also for overridden behavior in benign cases. For this to succeed, programs need to be in a certain normal form. The required normal form turns out to be achievable in many cases by a set of program transformations, whose correctness is ensured by the recent technique of abstract execution. This is a generalization of symbolic execution that permits reasoning about abstract code elements. It is needed, because code deltas contain partially unknown code contexts in terms of “original” calls. Second, we devise a modular verification procedure for deltas based on abstract execution, representing deltas as abstract programs calling into unknown contexts. The result is a “delta-based” verification approach, where each modification of a method in a code delta is verified in isolation, but which overcomes the strict limitations of behavioral subtyping and works for many practical programs. The latter claim is substantiated with case studies and benchmarks
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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