Repurposing Visual Input Modalities for Blind Users: A Case Study of Word Processors

Visual \u27point-and-click\u27 interaction artifacts such as mouse and touchpad are tangible input modalities, which are essential for sighted users to conveniently interact with computer applications. In contrast, blind users are unable to leverage these visual input modalities and are thus limited while interacting with computers using a sequentially narrating screen-reader assistive technology that is coupled to keyboards. As a consequence, blind users generally require significantly more time and effort to do even simple application tasks (e.g., applying a style to text in a word processor) using only keyboard, compared to their sighted peers who can effortlessly accomplish the same tasks using a point-and-click mouse. This paper explores the idea of repurposing visual input modalities for non-visual interaction so that blind users too can draw the benefits of simple and efficient access from these modalities. Specifically, with word processing applications as the representative case study, we designed and developed NVMouse as a concrete manifestation of this repurposing idea, in which the spatially distributed word-processor controls are mapped to a virtual hierarchical \u27Feature Menu\u27 that is easily traversable non-visually using simple scroll and click input actions. Furthermore, NVMouse enhances the efficiency of accessing frequently-used application commands by leveraging a data-driven prediction model that can determine what commands the user will most likely access next, given the current \u27local\u27 screen-reader context in the document. A user study with 14 blind participants comparing keyboard-based screen readers with NVMouse, showed that the latter significantly reduced both the task-completion times and user effort (i.e., number of user actions) for different word-processing activities

Precise specification matching for adaptive reuse in embedded systems

AbstractSpecification matching is a key to reuse of components in embedded systems. Existing specification matching techniques for embedded systems are designed to match reactive behaviors using adaptive techniques to dynamically alter behaviors. However, correct specification matching demands both behavioral matching (that checks component adaptability) and functional matching (that ensures that proper functionality is reused). While approaches for behavioral matching exist, combined functional and behavioral matching during component reuse in embedded systems is lacking. This paper presents a precise specification matching, including both behavioral and functional matching. We introduce attributed labeled transition systems (ALTS) to formally specify component behavior and functionalities. Given ALTS of a new specification (a function F) and an existing component (a device D), a new refinement relation from F to D, called an S-matching relation, is proposed for precise specification matching. The existence of an S-matching relation is also shown to be a necessary and sufficient condition for the existence of a correct adapter to adapt D to match F both behaviorally and functionally. Automated component adaptation is facilitated by a matching tool implemented in a tabled logic programming environment, which provides distinct advantages for rapid implementation. Practical examples are given to illustrate how the concrete adapter is derived automatically from specification matching

Magnetic, orbital and charge ordering in the electron-doped manganites

The three dimensional perovskite manganites in the range of hole-doping $x > 0.5$ are studied in detail using a double exchange model with degenerate $e_g$ orbitals including intra- and inter-orbital correlations and near-neighbour Coulomb repulsion. We show that such a model captures the observed phase diagram and orbital-ordering in the intermediate to large band-width regime. It is argued that the Jahn-Teller effect, considered to be crucial for the region $x<0.5$, does not play a major role in this region, particularly for systems with moderate to large band-width. The anisotropic hopping across the degenerate $e_g$ orbitals are crucial in understanding the ground state phases of this region, an observation emphasized earlier by Brink and Khomskii. Based on calculations using a realistic limit of finite Hund's coupling, we show that the inclusion of interactions stabilizes th e C-phase, the antiferromagnetic metallic A-phase moves closer to $x=0.5$ while th e ferromagnetic phase shrinks in agreement with recent observations. The charge ordering close to $x=0.5$ and the effect of reduction of band-width are also outlined. The effect of disorder and the possibility of inhomogeneous mixture of competing states have been discussed.Comment: 42 pages, 16 figure

Justifying Proofs using Memo Tables

Tableau-based proof systems can be elegantly specified and directly executed by a tabled Logic Programming (LP) system. Our experience with the XMC model checker shows that such an encoding can be used to search for the existence of a proof very efficiently. However, the users of a tableau system are often interested in getting sufficient evidence (in terms of the tableau proof rules) on why a proof does or does not exist. In this paper, we address the problem of constructing such an evidence without introducing any additional computational overhead to the proof search. A tabled LP system maintains a memo table of &quot;lemmas&quot; that were tried and possibly proved during query evaluation. We propose the concept of justifier for extracting sufficient evidence for the truth or falsehood of literals in a logic program, by post-processing the memo tables created during query evaluation. Based on this logic program justifier, we showhow to construct evidence for the presence/absence of tableau in a tableau-based proof system. Weprovide experimental results showing the effectiveness of the justifier in constructing succinct evidence of the evaluation performed by the XMC model checker. Finally we discuss the role of the justifier as a programming abstraction for encoding efficient algorithms as tabled logic programs

Inductively verifying invariant properties of parameterized systems

10.1023/B:AUSE.0000017740.35552.88Automated Software Engineering112101-139ASOE

Logic based modeling and analysis of workflows (Extended Abstract)

We propose Concurrent Transaction Logic (CT R) as the language for specifying, analyzing, and scheduling of work ows. We show that both local and global properties of work ows can be naturally represented as CT R formulas and reasoning can be done with the use of the proof theory and the semantics of this logic. We describe a transformation that leads to an e cient algorithm for scheduling work ows in the presence of global temporal constraints, which leads to decision procedures for dealing with several safety related properties such as whether every valid execution of the work ow satises a particular property or whether a work ow execution is consistent with some given global constraints on the ordering of events in a work ow. We also provide tight complexity results on the running times of these algorithms

On the Nonexistence of Optimal Scheduling Strategies for Tabled Resolution

Tabled resolution augments Prolog-style SLDNF resolution for evaluating normal logic programs. At a high level the central idea in tabled evaluation is to maintain all the subgoal invocations in a call table and their computed answers in an answer table. By using answer tables for resolving subsumed subgoal invocations (i.e. subgoals that are particular instances of other subgoals in the call table) tabled resolution strategies can prevent infinite looping that happens in Prolog-style evaluation. Thus termination properties of tabled resolution is substantially better than that of Prolog. Moreover, unlike Prolog, tabled resolution can also avoid redundant computations and hence improve the running time of programs. Resolving subsumed subgoals against answers may require accessing answer tables that are either complete or incomplete (i.e., more answers remain to be added). Since it is far more efficient to retrieve from completed tables, scheduling strategies promote more frequent usage..

On the Optimality of Scheduling Strategies in Subsumption based Tabled Resolution

Subsumption-based tabled logic programming promotes more aggressive reuse of answer tables over variant-based tabling. However resolving subgoals against answers in tabled logic programming may require accessing incomplete answer tables (i.e., more answers remain to be added). In subsumption-based tabling it is far more efficient to retrieve from completed tables. Scheduling strategies promote more frequent usage of such tables by exercising control over access to incomplete tables. Different choices in the control can lead to different sets of proof trees in the search forest produced by tabled resolution. The net effect is that depending on the scheduling strategy used, tabled logic programs under subsumption can exhibit substantial variations in performance. In this paper we establish that for subsumption-basedtabled logic programming an optimal scheduling strategy does not exist -- i.e., they are all incomparable in terms of time and space performance. Subsumption-based tabled reso..

A Thread in Time Saves Tabling Time

The use of tabling in logic programming has been recognized as a powerful evaluation technique. Currently available tabling systems are mostly based on variant checks and hence are limited in their ability to recognize reusable subcomputations. Tabling systems based on call subsumption can yield superior performance by recognizing a larger set of reusable computations. However, a straightforward adaptation of the mechanisms used in variant-based systems to reuse these computations can in fact result in considerable performance degradation. In this paper we propose a novel organization of tables using Dynamic Threaded Sequential Automata (DTSA) which permits efficient reuse of previously computed results in a subsumptive system. We describe an implementation of the tables using DTSA and the associated access mechanisms. We also report experimental results which show that a subsumptive tabling system implemented by extending the XSB logic programmingsystem with our table access techniqu..