We consider the representation of temporal data based on tuple and attribute timestamping. We identify the requirements in modeling temporal data and elaborate on their implications in the expressive power of temporal query languages. We introduce a temporal relational data model where N1NF relations and attribute timestamping are used and one level of nesting is allowed. For this model, a nested relational tuple calculus (NTC) is defined. We follow a comparative approach in evaluating the expressive power of temporal query languages, using NTC as a metric and comparing it with the existing temporal query languages. We prove that NTC subsumes the expressive power of these query languages. We also demonstrate how various temporal relational models can be obtained from our temporal relations by NTC and give equivalent NTC expressions for their languages. Furthermore, we show the equivalence of intervals and temporal elements (sets) as timestamps in our model. © 1997 IEEE
Questions of what it means to do computation with situations and what aspects of situation theory makes this suitable as a novel programming paradigm have not been fully discussed in the literature. This is what we hope to initiate here.
Situation theory has been developed over the last decade and various versions of the theory have been applied to a number of linguistic issues. However, not much work has been Clone in regard to its computational aspects. In this paper, we review the existing approaches towards 'computational situation theory' with considerable emphasis on our own research. IntroductionSituation theory is an attempt to develop a mathematical theory of meaning which will clarify and resolve some tough problems in the study of language, information, logic, philosophy, and the mind [11]. It was first formulated in detail by Jon Barwise and John Perry in 1983 [12] and has matured over the last decade [25]. Various versions of the theory have been applied to a number of linguistic issues, resulting in what is commonly known as situation semantics [7,8,10,24,31,33,35,58]. The latter aims at the construction of a unified and mathematically rigorous theory of meaning, and the application of such a theory to natural languages.Mathematical and logical issues that arise within situation theory and situation semantics have been explored in numerous works [8,10,12,24,25,33]. In the past, the development of a mathematicM situation theory has been held back by a lack of availability of appropriate technical tools. But by now, the theory has assembled its mathematical foundations based on intuitions basicaLly coming from set theory and logic [1,8,24,26]. With a remarkably original view of information (which is fully adapted by situation theory) [28,29], a 'logic,' based not on truth but on information, is being developed [25]. This logic 1 will probably be an extension of first-order logic [5] rather than being an alternative to it.Individuals, properties, relations, spatio-temporal locations, and situations are basic constructs of situation theory. The world is viewed as a collection of objects, sets of objects, properties, and relations. Infons ('unit' facts) [26] are discrete items of information and situations are first-class objects which describe parts of the real world. Information flow is made possible by a network of abstract 'links' between high-order uniformities, viz. situation types. One of the distinguishing characteristics of situation theory vis-£-vis another influential semantic and logical tradition [27] is that 1 According to The Advanced Learner's Dictionary of Current English (by A. S. Hornby, E. V. Gatenby, and H. Wakefield, London, U.K.: Oxford University Press, 1958), logic is the science or art of reasoning, proof, and clear thinking. Thus, the commonly accepted equation logic = first-order logic is highly suspect. (Cf. [6] for an extended argument on this.) information content is context-dependent (where a context is a situation).All these features may be cast in a rich formalism for a computational framework based on situation theory. Yet, there have been few attempts to investigate this [17,33,40,46,49,52,59]. Questions of what it means to do computation with situations and what aspects of the theory makes t...
Recently, there have been some attempts towards developing programming languages based on situation theory. These languages employ situationtheoretic constructs with varying degrees of divergence from the ontology of the theory. In this paper, we review three of these programming languages. IntroductionThe development of programming languages based on situation theory [1,6] is a new trend. For this reason, it is worth examining how much these programming languages reflect situation-theoretic concepts and how much they deviate from them. In this paper, we review three approaches [9,4,12] towards programming systems based on situation theory, viz. PROSIT, ASTL, and BABY-SIT, respectively. PKOSITPROSIT (PROgramming in Situation Theory), developed by Nakashima et al. [8,9,10], is tile first situation-theoretic programming language. It is a declarative language in which both programs and data are just sets of declarative elements. This feature makes PROSIT akin to PROLOG, but PROSIT is based on situation theory [1, 2, 6] instead of Horn clauses. The motivation behind +the design of this new language rests on the following features:0 The use of partially specified objects (e.g., situations) and partial information ® Situations as 'first-class citizens' of the theory • Informational constraints ® Self-referential expressions In PROSIT, an infon (a discrete item of information) is represented as a list whose first element is the relation and whose remaining elements are the arguments of the relation: object,).For example, the infon (listening-to John Mary) expresses that the relation listening-to holds between the objects represented by John and Mary, i.e., John is listening to Mary.One can assert infons and make queries about them. Unlike PROLOG, all infons are local to situations. For example, to ~sert the infon mentioned above in situation sitl the following expression is used:Expressions in PROSIT are LISP-style objects (i.e., atoms or lists). Atoms that are numbers or strings are considered Murat Ersan Department of Computer ScienceBrown University Providence, RI 02912-1910, USA me@cs.brown.edu to be constants. Symbols starting with a character other than "*" are parameters. They are used to represent things in the world, such as individuals, situations, and relations. Usually, different parameters correspond to different entities. Parameters can be used in any infon including queries and constraints; their scope is global. A third kind of expression is a variable. Variables axe represented with symbols starting with "*'. They can only occur in queries and constraints. They can stand for any PROSIT expression, yet their scope is local to the constraint or query they participate in.In PROSIT, there exists a tree hierarchy among all situations, where the situation top is at the root of the tree. top is the global situation and the 'owner' of all the other situations generated. One can traverse the 'situation tree' using the predicates in and out. Although it is possible to make queries from any situation abou...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.