The logic of identity and copy for computational artefacts

Defining identity for entities is a longstanding logical problem in philosophy, and it has resurfaced in current investigations within the philosophy of technology. The problem has not yet been explored for the philosophy of information, and of Computer Science in particular. This paper provides a logical analysis of identity and copy for computational artefacts. Identity is here understood as the relation holding between an instance of a computational artefact and itself. By contrast, the copy relation holds between two distinct computational artefacts. We distinguish among exact, inexact and approximate copies. We use process algebra to provide suitable formal definitions of these relations, using in particular the notion of bisimulation to define identity and exact copies, and simulation for inexact and approximate copies. Equivalence is unproblematic for identical computational artefacts at each individual time and for inexact copies; we will examine to which extent the formal constraints on identity criteria discussed in the literature are satisfied by our approach. As for inexact and approximate copy, they are intended as a weakening of the identity relation in that equivalence and other constraints on identity are violated. The proposed approach also suggests a computable treatment of identity and copy checking

The logic of identity and copy for computational artefacts

Defining identity for entities is a longstanding logical problem in philosophy, and it has resurfaced in current investigations within the philosophy of technology. The problem has not yet been explored for the philosophy of information, and of Computer Science in particular. This paper provides a logical analysis of identity and copy for computational artefacts. Identity is here understood as the relation holding between an instance of a computational artefact and itself. By contrast, the copy relation holds between two distinct computational artefacts. We distinguish among exact, inexact and approximate copies. We use process algebra to provide suitable formal definitions of these relations, using in particular the notion of bisimulation to define identity and exact copies, and simulation for inexact and approximate copies. Equivalence is unproblematic for identical computational artefacts at each individual time and for inexact copies; we will examine to which extent the formal constraints on identity criteria discussed in the literature are satisfied by our approach. As for inexact and approximate copy, they are intended as a weakening of the identity relation in that equivalence and other constraints on identity are violated. The proposed approach also suggests a computable treatment of identity and copy checking

Semantic study of spatial and temporal expressions in English

An investigation into the semantic systems underlying spatial and temporal expressions in confronted with two major problems: the interplay of contextual factors in determining the interpretation of particular expressions and the inter-relations between the two semantic systems. The first of these in a recurrent theme through- out the dissertation; the second underlies its organization and orientation. We begin, in Chapter 2, with a discussion of three recent studies on the semantics of spatial expressions in English. The conclusion is reached that more explicit attention must be given to the role of the intra-sentential context and, in particular, to the kind of situation being described by the sentence in which the expression occurs. We also recognize the need to give an explicit and comprehensive characterization of the notion of a journey, which latter in prerequisite to an understanding of such functional semantic elements an SOURCE, GOAL, PATH. Chapter 3 in devoted to the semantic analysis of static uses of locational and directional expressions. A tri-partite distinction is made between direct locational expressions (e.g. 'at the Post office) a semi-direct locational expressions (e.g. in front of the Post office"), and indirect locational expressions (e.g. above the Post office), Static directional expressions (e.g. towards the post office') are subsumed within indirect locational expressions. The orientational properties of the speaker/observer are found to be crucial to the analysis of the meanings of semi-direct and indirect locational expressions. Chapter 4 sets forth the historical background of the localist, hypothesis and surveys more recent arguments of a semantic and syntactic nature which have been given in support of it. According to the hypothesis, grammatical relations or functions, whether abstract or concrete, are ultimately describable in terms of spatial notions. The thesis of localism in set within a more encompassing theory of egocentric and anthropocentric extension operative throughout the language. Chapter 5 enumerates and discusses the major contextual elements within the sentence which interact with the co-occurrence and interpretation potential of temporal adverbial. These comprise tense, the progressive form, negation, spatial adverbials, referential proportion of the noun phrases and lexical properties of the verb. Chapter 6 redirects the focus to aspectual categories and to different kinds of propositions which some of the other contextual elements isolated in Chapter 5 participate in defining and with reference to which generalizations regarding co-occurrence and interpretations become statable. The logico-philocaphical tradition with respect to verb classification is surveyed and then the linguistic literature an aspect, aktionsartan, and verb classes. It is suggested that a distinction be made between aspect, aktionsartan, and proposition types, what is common to these three categories being the role played by the concepts of existential status and change of existential status in their characterizations. Chapter 7 begins with an inforual characterization of a journey, first in its most concrete and idealized manifestation an a point moving from one point to another. The extension of locational relations, direction, directed movementl, and journey to more abstract domains, including most importantly the existential and the temporal, is explored. The notion of existential location in incorporated into a descriptive apparatus for the semantics of expressions of physical extension in one dimension. This same notion also leads to a natural interpretation of negation, quantification, aspect and aktionearten and provides for a precise fomulation of, a. journey. A more generalized characterization of a journey in given which takes into account the extension of the moving object. A localist classification of proposition types in proposed. Chapter,. 8 applies the framework developed in Chapter 7 to the analysis of tense and to the description of two selected note of CkYT , lov%seadverbials: , (I) 'still! # Oyetlp IalreadyIq 13353M= and and (2) *until* and 'since** 'Chapter 9 onumerates, the main findings of the investigation* to the kind of situation being doscribed by the sentence in which thO OxPr0, 8sion occurs* We also recognize the need to give an explicit and comprehensive characterization of the notion of a journeyp which latter in prerequisite to an understanding of such functional semantic elements an SOURCE9G OAL9P ATH. Chapter 3 in devoted to the semantic analysis of static us* of locational and directional expressions. A tri. partits distinction is made between direct locational, expressions (soge 'at the Post office)q semi-direct locational expressions (sege Un frOist of the I)Oat office"), and indirect locational expressions (soge labove the Post offiest), Static directional expressions (*4, ge #towards the post office') are subsumed within indirect locational expressionse The orientational properties of the speaker/observer are found U) be crucial to the analysis of the meanings of semi. -direct and indirect locational, expressions. Chapter 4 sets forth the historical background of the localist, (ii) hypothesis and surveys nors, recent arguments of a semantic and syntactic nature which have been given in support of it* According to the hypothesis# grammatical relations or functionsp whether abstract or concretes are ultimately describable in terms of spatial notionse The thesis of localism in set within a more encompassing theory of egocentric and anthropocentric extension operative throughout the language. Chapter 5 enumerates and discusses the major contextual elements within the sentence which interact with the co-occurrence and interpretation potential of temporal adverbial@* These comprise tonset the progressive forms negationg spatial adverbialsq referential proportion of the noun phrases and lexical properties of the verb* Chapter 6 redirects the focus to aspectual categories and tw different kinds of propositions which some of the other contextual elements isolated in Chapter 5 participate in defining and with reference to which generalizations regarding oo-occurrence and interpretations become statablee The logico-philocaphical tradition with respect to verb classification is surveyed and then the linguistic literature an aspectq aktionsartang and verb classes* It in suggested that a distinction be made between aspootp aktionsarteng and proposition types, what in coitmon to these three categories being the role played by the concepts of existential status and change of existential status in their characterizations. Chapter 7 begins with an inforual characterization of a journeyp first in its most concrete and idealized manifestation an a point moving from one point to another* The extension of locatiOnal roletionag directiong directed movementl, and journey to more abstract domainag including most importantly the existential and the temporal* is *xplorede The notion of existential location in incorporated (iii) into a descriptive apparatus for the semantics of expressions of physical extension in one dimension* This same notion also leads to a natural interpretation of negationg quantificationg aspect and aktionearten and provides for a precise fomulation of, a. JournOY9 A more generalized characterization of a journey in given which takes into account the extension of the moving objooto A 10cali8t classification of proposition types in proposed* Chapter,. 8 applies the framework developed in Chapter 7 to the analysis of tans* and to the description of two selected note of CkYT , lov%seadverbials: , (I) 'still! # Oyetlp IalreadyIq 13353M= and and (2) *until* and 'since** 'Chapter 9 onumerates, the main findings of the investigation