A metalogic programming approach: language,semantics and applications

Abstract

This paper presents a logic programming language of novel conception, called Reflective Prolog, which allows declarative metaknowledge representation and metareasoning. The language is defined by augmenting pure Prolog (Horn clauses) with capabilities of self-reference and logical reflection. Self-reference is designed as a quotation device (a carefully defined naming relation) which allows the construction of metalevel terms that refer to object-level terms and atoms. Logical reflection is designed as an unquotation mechanism (a distinguished truth predicate) which relates names to what is named, thus extending the meaning of domain predicates. The reflection mechanism is embodied in an extended resolution procedure which automatically switches the context between levels. This implicit reflection relieves the programmer from having to explicitly deal with control aspects of the inference process. The declarative semantics of a Reflective Prolog definite program P is provided in terms of the least reflective Herbrand model of P, characterized by means of a suitable mapping defined over the Herbrand interpretations of P. The extended resolution is proved sound and complete with respect to the least reflective Herbrand model. By illustrating Reflective Prolog solutions to an organic set of problems, and by discussing the main differences with respect to other approaches to logic metaprogramming, we show that the proposed language deploys, within its field of action, greater expressive and inferential power than those available till now. The interpreter of the language has been fully implemented. Because of its enhanced power, logic semantics and working interpreter, Reflective Prolog is offered as a contribution toward making the declarative approach of logic programming applicable to the development of increasingly sophisticated knowledge-based systems.     

基于语义的自然语言文本数字水印研究

数字水印技术是信息隐藏技术研究领域的重要分支,也是当今网络信息安全和数字媒体版权保护研究的重要手段之一。目前数字水印技术的研究主要集中在静止图像和视频的保护等方面,文本数字水印研究较少。针对自然语言文本自身的特性,分析和比较了目前主要的文本数字水印方法及其技术特点,提出了文本数字水印的理论目标和攻击模型,给出了一种基于语义的文本数字水印算法,最后展望了文本数字水印技术研究的发展前景。     

Towards a natural language semantics without functors and operands

The paper sets out to offer an alternative to the function/argument approach to the most essential aspects of natural language meanings. That is, we question the assumption that semantic completeness (of, e.g., propositions) or incompleteness (of, e.g., predicates) exactly replicate the corresponding grammatical concepts (of, e.g., sentences and verbs, respectively). We argue that even if one gives up this assumption, it is still possible to keep the compositionality of the semantic interpretation of simple predicate/argument structures. In our opinion, compositionality presupposes that we are able to compare arbitrary meanings in term of information content. This is why our proposal relies on an ‘intrinsically’ type free algebraic semantic theory. The basic entities in our models are neither individuals, nor eventualities, nor their properties, but ‘pieces of evidence’ for believing in the ‘truth’ or ‘existence’ or ‘identity’ of any kind of phenomenon. Our formal language contains a single binary non-associative constructor used for creating structured complex terms representing arbitrary phenomena. We give a finite Hilbert-style axiomatisation and a decision algorithm for the entailment problem of the suggested system.     

自然语言语义理解在反垃圾邮件中的应用

在分析了基于统计的垃圾邮件分类中关键词的语义缺失问题后,提出将基于本体的自然语言语义理解应用于反垃圾邮件中,以解决关键词的语义问题。经过对垃圾邮件的特征进行分析,设计了关键词驱动的句法分析及基于本体的语义推理,在一定程度上解决了邮件过滤过程中词和句子的语义缺失,为垃圾邮件过滤提供了有益的探索。     

Predicate logic with flexibly binding operators and natural language semantics

A new formalism for predicate logic is introduced, with a non-standard method of binding variables, which allows a compositional formalization of certain anaphoric constructions, including donkey sentences and cross-sentential anaphora. A proof system in natural deduction format is provided, and the formalism is compared with other accounts of this type of anaphora, in particular Dynamic Predicate Logic.Both authors have been supported by grants from the Swedish Council for Research in the Humanities and Social Sciences.     

Algebraic structure of some stochastic discrete event systems,with applications

Generalized semi-Markov processes (GSMPs) and stochastic Petri nets (SPNs) are generally regarded as performance models (as opposed to logical models) of discrete event systems. Here we take the view that GSMPs and SPNS are essentially automata (generators) driven by input sequences that determine the timing of events. This view combines the deterministic, logical aspects and the stochastic, timed aspects of the two models. We focus on two conditions, (M) and (CX) (which we previously developed to study monotonicity and convexity properties of GSMPs), and the antimatroid and lattice structure they imply for the language generated by a GSMP or SPN. We illustrate applications of these structural properties in the areas of derivative estimation, simulation variance reduction, parallel simulation, and optimal control.Research supported in part by NSF grant ECS-89-96230.     

Algebraic tools for language processing

A language space provides a unified framework to deal with the properties of language constructs by associating them with their specification rules. The concrete syntax is represented by segments of the language space. The semantics is given by derived operations of the algebras where these constructs are interpreted by the processing tools operating on the language space. We examine in this paper only processing tools that collect syntactic information over the language space. Tools involved in semantics processing such as translators and interpreters are also integrated in the language space but are not discussed here.     

Computability concepts for programming language semantics

This paper is about mathematical problems in programming language semantics and their influence on recursive function theory. We define a notion of computability on continuous higher types (for all types) and show its equivalence to effective operators. This resuit shows that our computable operators can model mathematically (i.e. extensionally) everything that can be done in an operational semantics. These new recursion theoretic concepts which are appropriate to semantics also allow us to construct Scott models for the λ-calculus which contain all and only computably elements. Depending on the choice of the initial cpo, our general theory yields a theory for either strictly determinate or else arbitrary non-deterministic objects (parallelism). The formal theory is developed in Part II of this paper. Part I gives motivation and comparison with related work.     

CUDL language semantics: Updating FDB data

The semantics for data manipulation of the database language CUDL - Conceptual Universal Database Language - designed to manage dynamic database environments, are presented. This language conforms to the FDB (Frame DataBase) data model, offering a simple, easy and efficient platform for the use of the FDB model. Otherwise the management and operation of FDB data is laborious and time-consuming and it requires from the user a very good acquaintance of the proposed model, the structures and organisation of it as well as the processes of the management of elements that compose it. In this paper we present in depth the semantics of the way of handling the data, in order to search and transform information, in an FDB data source. We present the analysis of simple and complex cases that led us to synthesize valid and simple semantic rules that determine the data manipulation operations. The more sophisticated and demanding constructs, used in the language, for query specification, query processing and object manipulation are discussed and evaluated.     

Execution levels for aspect-oriented programming: Design,semantics, implementations and applications

In aspect-oriented programming (AOP) languages, advice evaluation is usually considered as part of the base program evaluation. This is also the case for certain pointcuts, such as if pointcuts in AspectJ, or simply all pointcuts in higher-order aspect languages like AspectScheme. While viewing aspects as part of base level computation clearly distinguishes AOP from reflection, it also comes at a price: because aspects observe base level computation, evaluating pointcuts and advice at the base level can trigger infinite regression. To avoid these pitfalls, aspect languages propose ad-hoc mechanisms, which increase the complexity for programmers while being insufficient in many cases. After shedding light on the many facets of the issue, this paper proposes to clarify the situation by introducing levels of execution in the programming language, thereby allowing aspects to observe and run at specific, possibly different, levels. We adopt a defensive default that avoids infinite regression, and gives advanced programmers the means to override this default using level-shifting operators. We then study execution levels both in practice and in theory. First, we study the relevance of the issues addressed by execution levels in existing aspect-oriented programs. We then formalize the semantics of execution levels and prove that the default semantics is indeed free of a certain form of infinite regression, which we call aspect loops. Finally, we report on existing implementations of execution levels for aspect-oriented extensions of Scheme, JavaScript and Java, discussing their implementation techniques and current applications.     

Linking operational semantics and algebraic semantics for a probabilistic timed shared-variable language

Complex software systems typically involve features like time, concurrency and probability, with probabilistic computations playing an increasing role. However, it is currently challenging to formalize languages incorporating all those features. Recently, the language PTSC has been proposed to integrate probability and time with shared-variable concurrency (Zhu et al. (2006, 2009) [51] and [53]), where the operational semantics has been explored and a set of algebraic laws has been investigated via bisimulation. This paper investigates the link between the operational and algebraic semantics of PTSC, highlighting both its theoretical and practical aspects.The link is obtained by deriving the operational semantics from the algebraic semantics, an approach that may be understood as establishing soundness of the operational semantics with respect to the algebraic semantics. Algebraic laws are provided that suffice to convert any PTSC program into a form consisting of a guarded choice or an internal choice between programs, which are initially deterministic. That form corresponds to a simple execution of the program, so it is used as a basis for an operational semantics. In that way, the operational semantics is derived from the algebraic semantics, with transition rules resulting from the derivation strategy. In fact the derived transition rules and the derivation strategy are shown to be equivalent, which may be understood as establishing completeness of the operational semantics with respect to the algebraic semantics.That theoretical approach to the link is complemented by a practical one, which animates the link using Prolog. The link between the two semantics proceeds via head normal form. Firstly, the generation of head normal form is explored, in particular animating the expansion laws for probabilistic interleaving. Then the derivation of the operational semantics is animated using a strategy that exploits head normal form. The operational semantics is also animated. These animations, which again supports to claim soundness and completeness of the operational semantics with respect to the algebraic, are interesting because they provide a practical demonstration of the theoretical results.     

An axiomatic semantics for the synchronous language Gentzen

We propose an axiomatic semantics for the synchronous language Gentzen, which is an instantiation of the paradigm Timed Concurrent Constraint Programming proposed by Saraswat, Jagadeesan and Gupta. We view Gentzen as a prototype of the class of state-oriented synchronous languages, since it offers the basic constructs that are shared by the languages in the class. Since synchronous concurrency cannot be simulated by arbitrary interleaving, we cannot exploit “head normal forms”, on which axiomatic theories for asynchronous process calculi are based. We suggest how axiomatic semantics for other state-oriented synchronous languages can be obtained by expressing constructs of such languages in terms of Gentzen constructs.     

A layered semantics for a parallel object-oriented language

We develop a denotational semantics for POOL, a parallel object-oriented programming language. The main contribution of this semantics is an accurate mathematical model of the most important concept in object-oriented programming: the object. This is achieved by structuring the semantics in layers working at three different levels: for statements, objects and programs. For each of these levels we define a specialized mathematical domain of processes, which we use to assign a meaning to each language construct. This is done in the mathematical framework of complete metric spaces. We also define operators that translate between these domains. At the program level we give a precise definition of the observable input/output behaviour of a particular program, which could be used at a later stage to decide the issue of full abstractness. We illustrate our semantic techniques by first applying them to a toy language similar to CSP.This paper describes work done in ESPRIT Basic Research Action 3020,Integration.     

Nivel: a metamodelling language with a formal semantics

Much work has been done to clarify the notion of metamodelling and new ideas, such as strict metamodelling, distinction between ontological and linguistic instantiation, unified modelling elements and deep instantiation, have been introduced. However, many of these ideas have not yet been fully developed and integrated into modelling languages with (concrete) syntax, rigorous semantics and tool support. Consequently, applying these ideas in practice and reasoning about their meaning is difficult, if not impossible. In this paper, we strive to add semantic rigour and conceptual clarity to metamodelling through the introduction of Nivel, a novel metamodelling language capable of expressing models spanning an arbitrary number of levels. Nivel is based on a core set of conceptual modelling concepts: class, generalisation, instantiation, attribute, value and association. Nivel adheres to a form of strict metamodelling and supports deep instantiation of classes, associations and attributes. A formal semantics is given for Nivel by translation to weight constraint rule language (WCRL), which enables decidable, automated reasoning about Nivel. The modelling facilities of Nivel and the utility of the formalisation are demonstrated in a case study on feature modelling.

An operational semantics for Icon: Implementation of a procedural goal-directed language

The generation of compiled code for expressions in programming languages such as Icon that support goal-directed evaluation in addition to traditional control structures presents more of a challenge than generating code for traditional imperative programming languages. This paper describes a code-generation technique for translating Icon programs into a traditional high-level language. Translations into both Pascal and C are discussed. However, any language that provides function parameters and recursion is sufficient. The technique described here has been used in the implementation of an optimizing compiler for Icon.     

The red and black semantics: a fuzzy language

The complexity of abstract art languages create new semantics in art. This model tries to implement its conceptual language within creating a new virtual environment. The gap between art and technology has been approached with a fuzzy logic engine which uses a red and black semantic codification. The examples include the application of this metalanguage to a virtual artwork experimentation.     

Preference update for e-commerce applications: Model,language, and processing

It is likely that customers issue requests based on out-of-date information in e-commerce application systems. Hence, the transaction failure rates would increase greatly. In this paper, we present a preference update model to address this problem. A preference update is an extended SQL update statement where a user can request the desired number of target data items by specifying multiple preferences. Moreover, the preference update allows easy extraction of criteria from a set of concurrent requests and, hence, optimal decisions for the data assignments can be made. We propose a group evaluation strategy for preference update processing in a multidatabase environment. The experimental results show that the group evaluation can effectively increase the customer satisfaction level with acceptable cost. Peng Li is the Chief Software Architect of didiom LLC. Before that, he was a visiting assistant professor of computer science department in Western Kentucky University. He received his Ph.D. degree of computer science from the University of Texas at Dallas. He also holds a B.Sc. and M.S. in Computer Science from the Renmin University of China. His research interests include database systems, database security, transaction processing, distributed and Internet computer and E-commerce. Manghui Tu received a Bachelor degree of Science from Wuhan University, P.R. China in 1996, and a Master Degree in Computer Science from the University of Texas at Dallas 2001. He is currently working toward the PhD degree in the Department of Computer Science at the University of Texas at Dallas. Mr. Tu’s research interests include distributed systems, grid computing, information security, mobile computing, and scientific computing. His PhD research work focus on the data management in secure and high performance data grid. He is a student member of the IEEE. I-Ling Yen received her BS degree from Tsing-Hua University, Taiwan, and her MS and PhD degrees in Computer Science from the University of Houston. She is currently an Associate Professor of Computer Science at the University of Texas at Dallas. Dr. Yen’s research interests include fault-tolerant computing, security systems and algorithms, distributed systems, Internet technologies, E-commerce, and self-stabilizing systems. She had published over 100 technical papers in these research areas and received many research awards from NSF, DOD, NASA, and several industry companies. She has served as Program Committee member for many conferences and Program Chair/Co-Chair for the IEEE Symposium on Application-Specific Software and System Engineering & Technology, IEEE High Assurance Systems Engineering Symposium, IEEE International Computer Software and Applications Conference, and IEEE International Symposium on Autonomous Decentralized Systems. She is a member of the IEEE. Zhonghang Xia received the B.S. degree in applied mathematics from Dalian University of Technology in 1990, the M.S. degree in Operations Research from Qufu Normal University in 1993, and the Ph.D. degree in computer science from the University of Texas at Dallas in 2004. He is now an assistant professor in the Department of Computer Science, Western Kentucky University, Bowling Green, KY. His research interests are in the area of multimedia computing and networking, distributed systems, and data mining.     

A relational tsetlin machine with applications to natural language understanding

Journal of Intelligent Information Systems - Tsetlin machines (TMs) are a pattern recognition approach that uses finite state machines for learning and propositional logic to represent patterns. In...     

Polymorphic scenario-based specification models: semantics and applications

We present polymorphic scenarios, a generalization of a UML2-compliant variant of Damm and Harel??s live sequence charts (LSC) in the context of object-orientation. Polymorphic scenarios are visualized using (modal) sequence diagrams where lifelines may represent classes and interfaces rather than concrete objects. Their semantics takes advantage of inheritance and interface realization to allow the specification of most expressive, succinct, and reusable universal and existential inter-object scenarios for object-oriented system models. We motivate the use of polymorphic scenarios, formally define their trace-based semantics, and present their application for scenario-based testing and execution, as implemented in the S2A compiler developed at the Weizmann Institute of Science. We further discuss advanced semantic issues arising from the use of scenarios in a polymorphic setting, suggest possible extensions, present a UML profile to support polymorphic scenarios, consider the application of the polymorphic semantics to other variants of scenario-based specification languages, and position our work in the broader context of behavioral subtyping.     

UpStream: storage-centric load management for streaming applications with update semantics

This paper addresses the problem of minimizing the staleness of query results for streaming applications with update semantics under overload conditions. Staleness is a measure of how out-of-date the results are compared with the latest data arriving on the input. Real-time streaming applications are subject to overload due to unpredictably increasing data rates, while in many of them, we observe that data streams and queries in fact exhibit “update semantics” (i.e., the latest input data are all that really matters when producing a query result). Under such semantics, overload will cause staleness to build up. The key to avoid this is to exploit the update semantics of applications as early as possible in the processing pipeline. In this paper, we propose UpStream, a storage-centric framework for load management over streaming applications with update semantics. We first describe how we model streams and queries that possess the update semantics, providing definitions for correctness and staleness for the query results. Then, we show how staleness can be minimized based on intelligent update key scheduling techniques applied at the queue level, while preserving the correctness of the results, even for complex queries that involve sliding windows. UpStream is based on the simple idea of applying the updates in place, yet with great returns in terms of lowering staleness and memory consumption, as we also experimentally verify on the Borealis system.