OpenRaiser/Intern-Atlas huggingface dataset:
Declarative Semantics for Active Rules
Venue: arXiv cs.DB 2003
Year: 2003

In this paper we analyze declarative deterministic and non-deterministic semantics for active rules. In particular we consider several (partial) stable model semantics, previously defined for deductive rules, such as well-founded, max deterministic, unique total stable model, total stable model, and maximal stable model semantics. The semantics of an active program AP is given by first rewriting it into a deductive program P, then computing a model M defining the declarative semantics of P and, finally, applying `consistent' updates contained in M to the source database. The framework we propose permits a natural integration of deductive and active rules and can also be applied to queries with function symbols or to queries over infinite databases.
On the Abductive or Deductive Nature of Database Schema Validation and Update Processing Problems
Venue: arXiv cs.DB 2003
Year: 2003

We show that database schema validation and update processing problems such as view updating, materialized view maintenance, integrity constraint checking, integrity constraint maintenance or condition monitoring can be classified as problems of either abductive or deductive nature, according to the reasoning paradigm that inherently suites them. This is done by performing abductive and deductive reasoning on the event rules [Oli91], a set of rules that define the difference between consecutive database states In this way, we show that it is possible to provide methods able to deal with all these problems as a whole. We also show how some existing general deductive and abductive procedures may be used to reason on the event rules. In this way, we show that these procedures can deal with all database schema validation and update processing problems considered in this paper.
Dialogue as Discourse: Controlling Global Properties of Scripted Dialogue
Venue: arXiv cs.CL 2003
Year: 2003

This paper explains why scripted dialogue shares some crucial properties with discourse. In particular, when scripted dialogues are generated by a Natural Language Generation system, the generator can apply revision strategies that cannot normally be used when the dialogue results from an interaction between autonomous agents (i.e., when the dialogue is not scripted). The paper explains that the relevant revision operators are best applied at the level of a dialogue plan and discusses how the generator may decide when to apply a given revision operator.
The Geometric Thickness of Low Degree Graphs
Venue: arXiv cs.CG 2003
Year: 2003

We prove that the geometric thickness of graphs whose maximum degree is no more than four is two. All of our algorithms run in O(n) time, where n is the number of vertices in the graph. In our proofs, we present an embedding algorithm for graphs with maximum degree three that uses an n x n grid and a more complex algorithm for embedding a graph with maximum degree four. We also show a variation using orthogonal edges for maximum degree four graphs that also uses an n x n grid. The results have implications in graph theory, graph drawing, and VLSI design.
Abduction in Well-Founded Semantics and Generalized Stable Models
Venue: arXiv cs.LO 2003
Year: 2003

Abductive logic programming offers a formalism to declaratively express and solve problems in areas such as diagnosis, planning, belief revision and hypothetical reasoning. Tabled logic programming offers a computational mechanism that provides a level of declarativity superior to that of Prolog, and which has supported successful applications in fields such as parsing, program analysis, and model checking. In this paper we show how to use tabled logic programming to evaluate queries to abductive frameworks with integrity constraints when these frameworks contain both default and explicit negation. The result is the ability to compute abduction over well-founded semantics with explicit negation and answer sets. Our approach consists of a transformation and an evaluation method. The transformation adjoins to each objective literal $O$ in a program, an objective literal $not(O)$ along with rules that ensure that $not(O)$ will be true if and only if $O$ is false. We call the resulting program a {\em dual} program. The evaluation method, \wfsmeth, then operates on the dual program. \wfsmeth{} is sound and complete for evaluating queries to abductive frameworks whose entailment method is based on either the well-founded semantics with explicit negation, or on answer sets. Further, \wfsmeth{} is asymptotically as efficient as any known method for either class of problems. In addition, when abduction is not desired, \wfsmeth{} operating on a dual program provides a novel tabling method for evaluating queries to ground extended programs whose complexity and termination properties are similar to those of the best tabling methods for the well-founded semantics. A publicly available meta-interpreter has been developed for \wfsmeth{} using the XSB system.
Complexity Results on DPLL and Resolution
Venue: arXiv cs.LO 2004
Year: 2004

DPLL and resolution are two popular methods for solving the problem of propositional satisfiability. Rather than algorithms, they are families of algorithms, as their behavior depend on some choices they face during execution: DPLL depends on the choice of the literal to branch on; resolution depends on the choice of the pair of clauses to resolve at each step. The complexity of making the optimal choice is analyzed in this paper. Extending previous results, we prove that choosing the optimal literal to branch on in DPLL is Delta[log]^2-hard, and becomes NP^PP-hard if branching is only allowed on a subset of variables. Optimal choice in regular resolution is both NP-hard and CoNP-hard. The problem of determining the size of the optimal proofs is also analyzed: it is CoNP-hard for DPLL, and Delta[log]^2-hard if a conjecture we make is true. This problem is CoNP-hard for regular resolution.
Efficient Tree Layout in a Multilevel Memory Hierarchy
Venue: arXiv cs.DS 2004
Year: 2004

We consider the problem of laying out a tree with fixed parent/child structure in hierarchical memory. The goal is to minimize the expected number of block transfers performed during a search along a root-to-leaf path, subject to a given probability distribution on the leaves. This problem was previously considered by Gil and Itai, who developed optimal but slow algorithms when the block-transfer size B is known. We present faster but approximate algorithms for the same problem; the fastest such algorithm runs in linear time and produces a solution that is within an additive constant of optimal. In addition, we show how to extend any approximately optimal algorithm to the cache-oblivious setting in which the block-transfer size is unknown to the algorithm. The query performance of the cache-oblivious layout is within a constant factor of the query performance of the optimal known-block-size layout. Computing the cache-oblivious layout requires only logarithmically many calls to the layout algorithm for known block size; in particular, the cache-oblivious layout can be computed in O(N lg N) time, where N is the number of nodes. Finally, we analyze two greedy strategies, and show that they have a performance ratio between Omega(lg B / lg lg B) and O(lg B) when compared to the optimal layout.
Unfolding Partiality and Disjunctions in Stable Model Semantics
Venue: arXiv cs.AI 2004
Year: 2004

The paper studies an implementation methodology for partial and disjunctive stable models where partiality and disjunctions are unfolded from a logic program so that an implementation of stable models for normal (disjunction-free) programs can be used as the core inference engine. The unfolding is done in two separate steps. Firstly, it is shown that partial stable models can be captured by total stable models using a simple linear and modular program transformation. Hence, reasoning tasks concerning partial stable models can be solved using an implementation of total stable models. Disjunctive partial stable models have been lacking implementations which now become available as the translation handles also the disjunctive case. Secondly, it is shown how total stable models of disjunctive programs can be determined by computing stable models for normal programs. Hence, an implementation of stable models of normal programs can be used as a core engine for implementing disjunctive programs. The feasibility of the approach is demonstrated by constructing a system for computing stable models of disjunctive programs using the smodels system as the core engine. The performance of the resulting system is compared to that of dlv which is a state-of-the-art special purpose system for disjunctive programs.
Lock-free dynamic hash tables with open addressing
Venue: arXiv cs.DC 2004
Year: 2004

We present an efficient lock-free algorithm for parallel accessible hash tables with open addressing, which promises more robust performance and reliability than conventional lock-based implementations. ``Lock-free'' means that it is guaranteed that always at least one process completes its operation within a bounded number of steps. For a single processor architecture our solution is as efficient as sequential hash tables. On a multiprocessor architecture this is also the case when all processors have comparable speeds. The algorithm allows processors that have widely different speeds or come to a halt. It can easily be implemented using C-like languages and requires on average only constant time for insertion, deletion or accessing of elements. The algorithm allows the hash tables to grow and shrink when needed. Lock-free algorithms are hard to design correctly, even when apparently straightforward. Ensuring the correctness of the design at the earliest possible stage is a major challenge in any responsible system development. In view of the complexity of the algorithm, we turned to the interactive theorem prover PVS for mechanical support. We employ standard deductive verification techniques to prove around 200 invariance properties of our algorithm, and describe how this is achieved with the theorem prover PVS.
Semiclassical Quantum Computation Solutions to the Count to Infinity Problem: A Brief Discussion
Venue: arXiv cs.NI 2004
Year: 2004

In this paper we briefly define distance vector routing algorithms, their advantages and possible drawbacks. On these possible drawbacks, currently widely used methods split horizon and poisoned reverse are defined and compared. The count to infinity problem is specified and it is classified to be a halting problem and a proposition stating that entangled states used in quantum computation can be used to handle this problem is examined. Several solutions to this problem by using entangled states are proposed and a very brief introduction to entangled states is presented.
The KR-Benes Network: A Control-Optimal Rearrangeable Permutation Network
Venue: arXiv cs.NI 2004
Year: 2004

The Benes network has been used as a rearrangeable network for over 40 years, yet the uniform $N(2 \log N-1)$ control complexity of the $N \times N$ Benes is not optimal for many permutations. In this paper, we present a novel $O(\log N)$ depth rearrangeable network called KR-Benes that is {\it permutation-specific control-optimal}. The KR-Benes routes {\it every} permutation with the minimal control complexity {\it specific} to that permutation and its worst-case complexity for arbitrary permutations is bounded by the Benes; thus it replaces the Benes when considering control complexity/latency. We design the KR-Benes by first constructing a restricted $2 \log K +2$ depth rearrangeable network called $K$-Benes for routing $K$-bounded permutations with control $2N \log K$, $0 \leq K \leq N/4$. We then show that the $N \times N$ Benes network itself (with one additional stage) contains every $K$-Benes network as a subgraph and use this property to construct the KR-Benes network. With regard to the control-optimality of the KR-Benes, we show that any optimal network for rearrangeably routing $K$-bounded permutations must have depth $2 \log K + 2$, and therefore the $K$-Benes (and hence the KR-Benes) is optimal.
Solving Sparse, Symmetric, Diagonally-Dominant Linear Systems in Time $O (m^{1.31})$
Venue: arXiv cs.DS 2004
Year: 2004

We present a linear-system solver that, given an $n$-by-$n$ symmetric positive semi-definite, diagonally dominant matrix $A$ with $m$ non-zero entries and an $n$-vector $\bb $, produces a vector $\xxt$ within relative distance $ε$ of the solution to $A \xx = \bb$ in time $O (m^{1.31} \log (n κ_{f} (A)/ε)^{O (1)})$, where $κ_{f} (A)$ is the log of the ratio of the largest to smallest non-zero eigenvalue of $A$. In particular, $\log (κ_{f} (A)) = O (b \log n)$, where $b$ is the logarithm of the ratio of the largest to smallest non-zero entry of $A$. If the graph of $A$ has genus $m^{2θ}$ or does not have a $K_{m^θ} $ minor, then the exponent of $m$ can be improved to the minimum of $1 + 5 θ$ and $(9/8) (1+θ)$. The key contribution of our work is an extension of Vaidya's techniques for constructing and analyzing combinatorial preconditioners.
A Cartography for 2x2 Symmetric Games
Venue: arXiv cs.GT 2004
Year: 2004

A bidimensional representation of the space of 2x2 Symmetric Games in the strategic representation is proposed. This representation provides a tool for the classification of 2x2 symmetric games, quantification of the fraction of them having a certain feature, and predictions of changes in the characteristics of a game when a change in done on the payoff matrix that defines it.
Initial Experiences Re-Exporting Duplicate and Similarity Computation with an OAI-PMH aggregator
Venue: arXiv cs.DL 2004
Year: 2004

The proliferation of the Open Archive Initiative Protocol for Metadata Harvesting (OAI-PMH) has resulted in the creation of a large number of service providers, all harvesting from either data providers or aggregators. If data were available regarding the similarity of metadata records, service providers could track redundant records across harvests from multiple sources as well as provide additional end-user services. Due to the large number of metadata formats and the diverse mapping strategies employed by data providers, similarity calculation requirements necessitate the use of information retrieval strategies. We describe an OAI-PMH aggregator implementation that uses the optional ``<about>'' container to re-export the results of similarity calculations. Metadata records (3751) were harvested from a NASA data provider and similarities for the records were computed. The results were useful for detecting duplicates, similarities and metadata errors.
About Unitary Rating Score Constructing
Venue: arXiv cs.LG 2004
Year: 2004

It is offered to pool test points of different subjects and different aspects of the same subject together in order to get the unitary rating score, by the way of nonlinear transformation of indicator points in accordance with Zipf's distribution. It is proposed to use the well-studied distribution of Intellectuality Quotient IQ as the reference distribution for latent variable "progress in studies".
Design of a Community-based Translation Center
Venue: arXiv cs.HC 2004
Year: 2004

Interfaces that support multi-lingual content can reach a broader community. We wish to extend the reach of CITIDEL, a digital library for computing education materials, to support multiple languages. By doing so, we hope that it will increase the number of users, and in turn the number of resources. This paper discusses three approaches to translation (automated translation, developer-based, and community-based), and a brief evaluation of these approaches. It proposes a design for an online community translation center where volunteers help translate interface components and educational materials available in CITIDEL.
Heuristic average-case analysis of the backtrack resolution of random 3-Satisfiability instances
Venue: arXiv cs.DS 2004
Year: 2004

An analysis of the average-case complexity of solving random 3-Satisfiability (SAT) instances with backtrack algorithms is presented. We first interpret previous rigorous works in a unifying framework based on the statistical physics notions of dynamical trajectories, phase diagram and growth process. It is argued that, under the action of the Davis--Putnam--Loveland--Logemann (DPLL) algorithm, 3-SAT instances are turned into 2+p-SAT instances whose characteristic parameters (ratio alpha of clauses per variable, fraction p of 3-clauses) can be followed during the operation, and define resolution trajectories. Depending on the location of trajectories in the phase diagram of the 2+p-SAT model, easy (polynomial) or hard (exponential) resolutions are generated. Three regimes are identified, depending on the ratio alpha of the 3-SAT instance to be solved. Lower sat phase: for small ratios, DPLL almost surely finds a solution in a time growing linearly with the number N of variables. Upper sat phase: for intermediate ratios, instances are almost surely satisfiable but finding a solution requires exponential time (2 ^ (N omega) with omega>0) with high probability. Unsat phase: for large ratios, there is almost always no solution and proofs of refutation are exponential. An analysis of the growth of the search tree in both upper sat and unsat regimes is presented, and allows us to estimate omega as a function of alpha. This analysis is based on an exact relationship between the average size of the search tree and the powers of the evolution operator encoding the elementary steps of the search heuristic.
Using biased coins as oracles
Venue: arXiv cs.OH 2004
Year: 2004

While it is well known that a Turing machine equipped with the ability to flip a fair coin cannot compute more that a standard Turing machine, we show that this is not true for a biased coin. Indeed, any oracle set $X$ may be coded as a probability $p_{X}$ such that if a Turing machine is given a coin which lands heads with probability $p_{X}$ it can compute any function recursive in $X$ with arbitrarily high probability. We also show how the assumption of a non-recursive bias can be weakened by using a sequence of increasingly accurate recursive biases or by choosing the bias at random from a distribution with a non-recursive mean. We conclude by briefly mentioning some implications regarding the physical realisability of such methods.
A correct, precise and efficient integration of set-sharing, freeness and linearity for the analysis of finite and rational tree languages
Venue: arXiv cs.PL 2004
Year: 2004

It is well-known that freeness and linearity information positively interact with aliasing information, allowing both the precision and the efficiency of the sharing analysis of logic programs to be improved. In this paper we present a novel combination of set-sharing with freeness and linearity information, which is characterized by an improved abstract unification operator. We provide a new abstraction function and prove the correctness of the analysis for both the finite tree and the rational tree cases. Moreover, we show that the same notion of redundant information as identified in (Bagnara et al. 2002; Zaffanella et al. 2002) also applies to this abstract domain combination: this allows for the implementation of an abstract unification operator running in polynomial time and achieving the same precision on all the considered observable properties.
Automated Resolution of Noisy Bibliographic References
Venue: arXiv cs.DL 2004
Year: 2004

We describe a system used by the NASA Astrophysics Data System to identify bibliographic references obtained from scanned article pages by OCR methods with records in a bibliographic database. We analyze the process generating the noisy references and conclude that the three-step procedure of correcting the OCR results, parsing the corrected string and matching it against the database provides unsatisfactory results. Instead, we propose a method that allows a controlled merging of correction, parsing and matching, inspired by dependency grammars. We also report on the effectiveness of various heuristics that we have employed to improve recall.
Semantic Optimization of Preference Queries
Venue: arXiv cs.DB 2004
Year: 2004

The notion of preference is becoming more and more ubiquitous in present-day information systems. Preferences are primarily used to filter and personalize the information reaching the users of such systems. In database systems, preferences are usually captured as preference relations that are used to build preference queries. In our approach, preference queries are relational algebra or SQL queries that contain occurrences of the winnow operator ("find the most preferred tuples in a given relation"). We present here a number of semantic optimization techniques applicable to preference queries. The techniques make use of integrity constraints, and make it possible to remove redundant occurrences of the winnow operator and to apply a more efficient algorithm for the computation of winnow. We also study the propagation of integrity constraints in the result of the winnow. We have identified necessary and sufficient conditions for the applicability of our techniques, and formulated those conditions as constraint satisfiability problems.
MammoGrid: Large-Scale Distributed Mammogram Analysis
Venue: arXiv cs.SE 2004
Year: 2004

Breast cancer as a medical condition and mammograms as images exhibit many dimensions of variability across the population. Similarly, the way diagnostic systems are used and maintained by clinicians varies between imaging centres and breast screening programmes, and so does the appearance of the mammograms generated. A distributed database that reflects the spread of pathologies across the population is an invaluable tool for the epidemiologist and the understanding of the variation in image acquisition protocols is essential to a radiologist in a screening programme. Exploiting emerging grid technology, the aim of the MammoGrid [1] project is to develop a Europe-wide database of mammograms that will be used to investigate a set of important healthcare applications and to explore the potential of the grid to support effective co-working between healthcare professionals.
An Integrated Approach for Extraction of Objects from XML and Transformation to Heterogeneous Object Oriented Databases
Venue: arXiv cs.DB 2004
Year: 2004

CERN's (European Organization for Nuclear Research) WISDOM project uses XML for the replication of data between different data repositories in a heterogeneous operating system environment. For exchanging data from Web-resident databases, the data needs to be transformed into XML and back to the database format. Many different approaches are employed to do this transformation. This paper addresses issues that make this job more efficient and robust than existing approaches. It incorporates the World Wide Web Consortium (W3C) XML Schema specification in the database-XML relationship. Incorporation of the XML Schema exhibits significant improvements in XML content usage and reduces the limitations of DTD-based database XML services. Secondly the paper explores the possibility of database independent transformation of data between XML and different databases. It proposes a standard XML format that every serialized object should follow. This makes it possible to use objects of heterogeneous database seamlessly using XML.