In "Syntactic Control of Interference" (POPL, 1978), J. C. Reynolds proposes three design principles intended to constrain the scope of imperative state effects in Algol-like languages. The resulting linguistic framework seems to be a very satisfactory way of combining functional and imperative concepts, having the desirable attributes of both purely functional languages (such as pcf) and simple imperative languages (such as the language of while programs). However, Reynolds points out that the "obvious" syntax for interference control has the unfortunate property that fi-reductions do not always preserve typings. Reynolds has subsequently presented a solution to this problem (ICALP, 1989), but it is fairly complicated and requires intersection types in the type system. Here, we present a much simpler solution which does not require intersection types. We first describe a new type system inspired in part by linear logic and verify that reductions preserve typings. We then define a class...

In this paper, we motivate and present a data model for conceptual design of structural and behavioural aspects of databases. We follow an object centered design paradigm in the spirit of semantic data models. The specification of structural aspects is divided into modelling of object structures and modelling of data types used for describing object properties. The specification of object structures is based on an Extended Entity--Relationship (EER) model. The specification of behavioural aspects is divided into the modelling of admissible database state evolutions by means of temporal integrity constraints and the formulation of database (trans)actions. The central link for integrating these design components is a descriptive logic-- based query language for the EER model. The logic part of this language is the basis for static constraints and descriptive action specifications by means of pre- and postconditions. A temporal extension of this logic is the specification language for tem...

This paper formally presents a class of planning problems which allows non-binary state variables and parallel execution of actions. The class is proven to be tractable, and we provide a sound and complete polynomial time algorithm for planning within this class. This result means that we are getting closei to tackling realistic planning problems in sequential control, where a restricted problem representation is often sufficient, but where the size of the problems make tractability an important issue. 1

. After a short analysis of the requirements that a knowledge representation language must satisfy, we introduce Description Logics, Modal Logics, and Nonmonotonic Logics as formalisms for representing terminological knowledge, time-dependent or subjective knowledge, and incomplete knowledge respectively. At the end of each section, we briefly comment on the connection to Logic Programming. 1 Introduction This section is concerned with the question under which conditions one may rightfully claim to have represented knowledge about an application domain, and not just stored data occurring in this domain. 1 In the early days of Artificial Intelligence and Knowledge Representation, there was a heated discussion on whether logic can at all be used as a formalism for Knowledge Representation (see e.g. [135, 91, 92]). One aspect of the requirements on knowledge representation formalisms that can be derived from the considerations in this section is very well satisfied by logical for...

We define the SAS + planning formalism, which generalizes the previously presented SAS formalism. The SAS + formalism is compared with some better-known propositionalplanning formalisms with respect to expressiveness. Contrary to intuition, all formalisms turn out to be equally expressive in a very strong sense. We further present the SAS + -PUS planning problem which generalizes the previously presented, tractable SASPUS problem. We prove that also the SAS + - PUS problem is tractable by devising a provably correct polynomial time algorithm for this problem. 1 Introduction Much effort has gone into finding more and more general formalisms, mainly logic-based, for plans and actions and also into finding reasoning methods for these. Although such formalisms may be important for modelling problems and comparing different approaches we most probably have to identify subproblems and devise tailored algorithms for these in order to overcome the computational difficulties involved. ...

We review some logic formalisms which were designed in order to reason about situations, goals, and actions. In particular, we focuss on the so-called frame problem, i.e. the technical problem of how to formalize the assumption that unless an action explicitly causes a certain fact to hold or not to hold, the facts are preserved by the action. It is shown that there is no need to explicitly state frame axioms, ie. axioms which deal with the frame problem, if the logic formalism treats facts as resources which are produced and consumed. The linear connection method, the linear logic as well as a particular equational logic are such formalisms. Moreover, we demonstrate that these three formalisms are equivalent for a large class of planning problems.

Recently, three approaches to deductive planning were developed, which solve the technical frame problem without the need to state frame axioms explicitly. These approaches are based on the linear connection method, an equational Horn logic, and linear logic. At first glance these approaches seem to be very different. In the linear connection method a syntactical condition -- each literal is connected at most once -- is imposed on proofs. In the equational logic approach situations and plans are represented as terms and SLDE-resolution is applied as an inference rule. The linear logic approach is a Gentzen style proof system without weakening and contraction rules. On second glance, however, and as a consequence of the results rigourously proved in this paper, it will turn out that the three approaches are equivalent. They are based on the very same idea that facts about a situation are taken as resources which can be consumed and produced.

Declaration This dissertation is the result of my own work and includes nothing which is the outcome of work done in collaboration, except where stated. It has not been submitted in whole or part for a degree at any other university. The length of this thesis including footnotes and appendices does not exceed 29,500 words and includes no more than 40 figures. 1 Systems which automatically transcribe carefully dictated speech are now commercially available, but their performance degrades dramatically when the speaking style of users becomes more relaxed or conversational. This dissertation focuses on techniques that aim to improve the robustness of statistical speech transcription systems to conversational speaking styles. The dissertation shows first that the performance degradation occuring as speech becomes more conversational is severe and is partially attributable to differences in the acoustic realizations of sentences. Hypothesizing that the quantifiably wider range of

This report surveys the literature on decomposition of binary, multiple-valued, and fuzzy functions. It gives also references to relevant basic logic synthesis papers that concern topics important for decomposition, such as for instance representation of Boolean functions, or symmetry of Boolean functions. As a result of the analysis of the most successful decomposition programs for Ashenhurst-Curtis Decomposition, several conclusions are derived that should allow to create a new program that will be able to outperform all the existing approaches to decomposition. Creating such asuperior program is necessary to make it practically useful for applications that are of interest to Pattern Theory group at Avionics Labs of Wright Laboratories. In addition, the program will be also able to solve problems that have been never formulated before. It will be a test-bed to develop and compare several known and new partial ideas related to decomposition. Our emphasis is on the following topics: 1. representation of data and e cient algorithms for data manipulation, 2. variable ordering methods for variable partitioning to create bound and free sets of input variables � heuristic approaches and their comparison, 3. column compatibility problem, 4. subfunction encoding problem, 5. use of partial and total symmetries in data to decrease the decomposition search space, 6. methods of dealing with strongly unspeci ed functions which are typical for machine learning applications, 7. special types of decomposition, that can be e ciently handled (cascades, trees without variable repetition). 2 We would like toacknowledge Dr. Tim Ross, Mr. Mark Axtell, and Professors Robert Brayton,

This note revisits the identification theorems of B. Brown (1983) and Roehrig (1988). We describe an error in the proofs of the main identification theorems in these papers, and provide an important counterexample to the theorems on the identification of the reduced form. Specifically, contrary to the theorems, the reduced form of a nonseparable simultaneous equations model is not identified even under the assumptions of those papers. We conclude the note with a conjecture that it may be possible to use classical exclusion restrictions to recover some of the key implications of the theorems. ∗We have had very helpful conversations with Pat Bayer, Don Brown, Yossi Feinberg, Guido Imbens, Yuliy Sannikov, Andy Skrzypacz, and Chris Timmons. Any remaining In this note, we reconsider the nonparametric identification of nonlinear simultaneous equations models, as in B. Brown (1983) and Roehrig (1988). We