Closed-World Assumption

SQL is the (more or less) standardised language that is used by the majority of commercial database management systems. However, it is seriously flawed, as has been documented in detail by Date, Darwen, Pascal, and others. One of the most serious problems with SQL is the way it handles missing data. It uses a special value 'NULL ' to represent data items whose value is not known. This can have a variety of meanings in different circumstances (such as 'inapplicable ' or 'unknown'). The SQL language also allows an 'unknown ' truth value in logical expressions. The resulting incomplete three-valued logic leads to inconsistencies in data handling within relational database management systems. Relational database theorists advocate that a strict two-valued logic (true/false) be used instead, with prohibition of the use of NULL, and justify this stance by assertion that it is a true representation of the 'real world'. Nevertheless, in real...

Pretend play is often defined as an imaginative play that involves acting as if : for example, pretending to work would be analysed as “acting as if one was working”. The question on how human beings understand pretence becomes particularly interesting, as soon as one realises that 24 months old children are able to engage in basics forms of pretend play.

In the attempt to clarify what acting as if means, the present work deconstructs pretence in terms of simpler reasoning processes, i.e. the ones that children display when they start engaging in pretend plays. This deconstruction is guided by experimental results about imagination, hypothetical reasoning and pretence in early childhood. At the same time, the theoretical analysis of these imaginative phenomena is directed towards a logical formalisation of pretence. I suggest that the logic based on closed world reasoning – i.e. the treating of all the information not currently considered or represented as false – used in this work displays how imagination, subtractive reasoning and pretend play are related.

Since autism is often diagnosed on the basis of a lack of pretence behaviour, part of the work is devoted to the investigation of how children with autism engage in pretend play. The union of psychological, philosophical and logical analysis, presented in this work, models the behaviour of both neuro-typical and children with autism, and generates a novel hypothesis on children’s understanding of pretence.

Social systems are more complex than physical systems but systems theory and cybernetics are not extensible by adding local refinements as an incremental science. By general systems theory we would expect living systems to exhibit the same fundamentals as physical systems that can be expressed in logical terms, that is the language of mathematics, science and philosophy built on logic. As the complexity of systems increases so the theory has to dig deeper into these logical foundations to guarantee a rigorous application of its principles. This applies to the systems of human life to be found in biology and medicine, economics and social systems, that is if they are to have the power of the exact sciences. Human life resides in a myriad of connections at various levels. Possible interactions between levels lead to a more profound type of logic because the closed world assumption no longer holds at any level. It is necessary therefore to go back to first principles even to the work o...

We present a new partial order planner called PSIPLAN, which builds on SNLP. We drop the closed world assumption, add sensing actions, add a class of propositions about the agent's knowledge, and add a class of universally quantified propositions. This latter class of propositions, which we call Ψ-forms, distinguishes this research, Ψ-forms represent partially closed worlds, such as "Block A is clear", or "x.ps is the only postscript file in directory /tex." We present our theory of planning with sensing and show how partial order planning is performed using Ψ-forms. Noteworthy are the facts that lack of information can be represented precisely and all quantified reasoning has polynomial complexity. Thus, in finite domains where the maximum plan length is bounded, planning with PSIPLAN is NP-complete.

In this paper, we study a new semantics of logic programming and deductive databases. Thepossible model semantics is introduced as a declarative semantics of disjunctive logic programs. The possible model semantics is an alternative theoretical framework to the classical minimal model semantics and provides a flexible inference mechanism for inferring negation in disjunctive logic programs. We also present a proof procedure for the possible model semantics and show that the possible model semantics has an advantage from the computational complexity point of view.

A faceted taxonomy is a set of taxonomies, each describing a given domain from a different aspect, or facet. The indexing of domain objects is done through conjunctive combinations of terms from the facets, called compound terms. A faceted taxonomy has several advantages over a single hierarchy of terms, including conceptual clarity, compactness and scalability. A drawback, however, is the cost of avoiding invalid combinations, i.e. compound terms that do not apply to any object in the domain. This need arises in both indexing and retrieval, and typically involves human effort for specifying the valid compound terms one by one. We here propose a compound term composition algebra which can be used to generate valid compound terms in a given faceted taxonomy in an efficient and flexible manner. It works on the basis of the original simple terms of the facets and a small set of positive and/or negative statements. In each algebraic operation, we adopt a closed-world assumption with res...

A faceted taxonomy is a set of taxonomies, each describing a given domain from a different aspect, or facet. The indexing of domain objects is done through conjunctive combinations of terms from the facets, called compound terms. A faceted taxonomy has several advantages over a single hierarchy of terms, including conceptual clarity, compactness and scalability. A drawback, however, is the cost of avoiding invalid combinations, i.e. compound terms that do not apply to any object in the domain. This need arises in both indexing and retrieval, and typically involves human effort for specifying the valid compound terms one by one. We here propose a compound term composition algebra which can be used to generate valid compound terms in a given faceted taxonomy in an efficient and flexible manner. It works on the basis of the original simple terms of the facets and a small set of positive and/or negative statements. In each algebraic operation, we adopt a closed-world assumption with res...

The Semantic Web (SW) can be seen as abstract representa- tion and exchange of data and metadata. Metadata is given in terms of data mark-up and reference to shared, Web-accessible ontologies. Sev- eral interesting languages are now available for the Semantic Web. They exploit XML allowing data/metadata communication, yet are endowed with a logical semantics. Such languages allow compact descriptions

Although information plays a major role in effective functioning of supply chain networks (SCNs), studies that deal specifically with the dynamics of supply chains are few. This problem is relatively new since fast communications and the means to employ it for effective management of supply chains did not exist till recently. In order to provide a vehicle for dynamic modelling and analysis of supply chain operations in vague and uncertain environments, we propose a fuzzy enhanced high level petri net (FEHLPN) model. The proposed model captures the capability of petri nets for graphical and analytical representation of dynamic SCNs with the management of uncertain information provided by fuzzy logic. The dynamics associated with two production planning and control policies are modelled, viz. make-to-stock and assemble-to-order in vague and ambiguous situations in electronic commerce environment. A fuzzy set and fuzzy truth-values are attached to an uncertain fuzzy token to model imprecision and uncertainty. The proposed FEHLPN incorporates essential aspects of rule-based systems, such as conservation of facts, refraction, and closed-world assumption.

Although information plays a major role in effective functioning of supply chain networks (SCNs), studies that deal specifically with the dynamics of supply chains are few. This problem is relatively new since fast communications and the means to employ it for effective management of supply chains did not exist till recently. In order to provide a vehicle for dynamic modelling and analysis of supply chain operations in vague and uncertain environments, we propose a fuzzy enhanced high level petri net (FEHLPN) model. The proposed model captures the capability of petri nets for graphical and analytical representation of dynamic SCNs with the management of uncertain information provided by fuzzy logic. The dynamics associated with two production planning and control policies are modelled, viz. make-to-stock and assemble-to-order in vague and ambiguous situations in electronic commerce environment. A fuzzy set and fuzzy truth-values are attached to an uncertain fuzzy token to model imprecision and uncertainty. The proposed FEHLPN incorporates essential aspects of rule-based systems, such as conservation of facts, refraction, and closed-world assumption.

Previous studies of incomplete XML documents have identified three main sources of incompleteness – in structural information, data values, and labeling – and addressed data complexity of answering analogs of unions of conjunctive queries under the open world assumption. It is known that structural incompleteness leads to intractability, while incompleteness in data values and labeling still permits efficient computation of certain answers. The goal of this paper is to provide a complete picture of the complexity of query answering over incomplete XML documents. We look at more expressive languages, at other semantic assumptions, and at both data and combined complexity of query answering, to see whether some well-behaving tractable classes have been missed. To incorporate non-positive features into query languages, we look at gentle ways of introducing negation via inequalities and/or Boolean combinations of positive queries, as well as the analog of relational calculus. We also lo...

Abstract—this work aims at bound geometrical detection of 3D objects from a point cloud using semantic descriptors to improve reusability of architectural building reconstruction and aid automatic reasoning in building information modeling (BIM). Based on exploring cognitive origins of ...

Ontologies and automated reasoning are the building blocks of the Semantic Web initiative. Derivation rules can be included in an ontology to define derived concepts, based on base concepts. For example, rules allow to define the extension of a class or property, based on a complex relation between the extensions of the same or other classes and properties. On the other hand, the inclusion of negative information both in the form of negation-as-failure and explicit negative information is also needed to enable various forms of reasoning. In this paper, we extend RDF graphs with weak and strong negation, as well as derivation rules. The ERDF stable model semantics of the extended framework (Extended RDF) is defined, extending RDF(S) semantics. A distinctive feature of our theory, which is based on Partial Logic, is that both truth and falsity extensions of properties and classes are considered, allowing for truth value gaps. Our framework supports both closed-world and open-world rea...

This research aims to examine adolescents’ world assumptions, personal attributes and gender roles. The research has attempted to examine the thoughts of adolescents about the world and the ways in which they define themselves as a man or a woman by considering the fact that their lives are affected not only by "traumatic" events but also by several family and environmental dynamics affecting their quality of life. Data was obtained from randomly selected 407 high school students from Kadıköy district in Istanbul province, by applying “World Assumptions Scale (WAS)”, “Extended Personal Attributes Questionnaire (EPAQ)”, “Gender Roles Attitude Scale (GRAS)”, and “Data Collection Form”. Our results showed that there was a significant difference in the scales and sub-dimensions used in the research with respect to gender, grade, family characteristics as well as life standards, balance of standards, adequacy of/change in family income, living with the family without problems, ...

We present a new,partial order planner called PSI- PLAN, which builds on SNLP. We drop the closed world assumption, add sensing actions, add a class of propositions about the agent’s knowledge, and add a class of universally quantified propositions. This lat- ter class of propositions, which we call ˆ-forms, dis- tinguishes this research. ˆ-forms represent partially closed worlds, such

The causal logic from (Bochman 2003b) is shown to provide a natural logical basis for logic programming. More exactly, it is argued that any logic program can be seen as a causal the- ory satisfying the Negation As Default principle (alias Closed World Assumption). Moreover, unlike well-known transla- tions of logic programs to other nonmonotonic formalisms, the established correspondence between

In this paper, we study an abductive framework for disjunctive logic programming that provides a new way to understand negation in disjunctive logic programming. We show that the defined framework captures the existing minimal model semantics based on (Extended) Generalised Closed World Assumption ((E)GGWA), This relationship between abduction and minimal model reasoning provides a methodology to develop algorithms for minimal model reasoning. To demonstrate this, we show how a theorem prover, based on restart model elimination calculus, can be modified for abductive reasoning and thus for minimal model reasoning.

In [11], we proposed an algebra with four algebraic operators, whose composition can be used to generate valid compound terms in a given faceted taxonomy in an efficient and flexible manner. The positive operations allow the derivation of valid compound terms through the declaration of a small set of valid compound terms. The negative operations allow the derivation of valid compound terms through the declaration of a small set of invalid compound terms. Here, we formally define the model-theoretic semantics of the operations and the closed-world assumptions adopted in each operation. We prove that our algebra is monotonic with respect to both valid and invalid compound terms, meaning that the valid and invalid compound terms of a subexpression are not invalidated by a larger expression. The importance of this property is demonstrated through an example. We also show that our algebra cannot be directly represented in Description Logics. A metasystem on top of Description Logics is designed to implement our algebra.

Standard databases convey Reiter's closed-world assumption that an atom not in the database is false. This assumption is relaxed in locally complete databases that are sound but only partially complete about their domain. One of the consequences of the weakening of the closed-world assumption is that query answering in locally closed databases is not tractable. In this paper we develop efficient approximate methods for query answering, based on fixpoint computations. We present preliminary results for a broad class of locally closed databases in which this method produces complete answers to queries.