15320762
Narratives in the Situation Calculus
A narrative is a course of real events about which we might have incomplete information. Formalisms for reasoning about action may be broadly divided into those which are narrative-based, such as the Event Calculus of Kowalski and Sergot, and those which reason on the level of hypothetical sequences of actions, in particular the Situation Calculus. This paper bridges the gap between these types of formalism by supplying a technique for linking incomplete narrative descriptions to Situation Calculus domain formulae written in the usual style using a Result function. Particular attention is given to actions with duration and overlapping actions. By illuminating the relationship between these two diierent styles of representation, the paper moves us one step closer to a full understanding of the space of all possible formalisms for reasoning about action.
10794263
E-RES: A System for Reasoning about Actions, Events and Observations
E-RES is a system that implements the Language E , a logic for reasoning about narratives of action occurrences and observations. E ’s semantics is modeltheoretic, but this implementation is based on a sound and complete reformulation of E in terms of argumentation, and uses general computational techniques of argumentation frameworks. The system derives sceptical non-monotonic consequences of a given reformulated theory which exactly correspond to consequences entailed by E ’s model-theory. The computation relies on a complimentary ability of the system to derive credulous non-monotonic consequences together with a set of supporting assumptions which is sufficient for the (credulous) conclusion to hold. E-RES allows theories to contain general action laws, statements about action occurrences, observations and statements of ramifications (or universal laws). It is able to derive consequences both forward and backward in time. This paper gives a short overview of the theoretical basis of E-RES and illustrates its use on a variety of examples. Currently, E-RES is being extended so that the system can be used for planning.
10913688
A Case Study in Reasoning about Actions and Continuous Change
This paper shows how the Situation Calculus can be extended to deal both with `narratives' and with domains containing real-valued parameters, whose actual values may vary continuously between the occurrences of actions. In particular, a domain is represented where action occurrences may be `triggered' at instants in time when certain parameters reach particular values. Its formalisation requires the integration of several types of default reasoning. Hence Baker's circumscriptive solution to the frame problem is extended to re ect the assumptions that by default a given action does not occur at a given time point, that by default a given set of parameter values does not trigger a given action, and that by default a given action occurrence does not result in a discontinuity for a given parameter. Regarding the minimisation of discontinuities, the example illustrates how circumstances can arise where, at a particular time point, discontinuities in some parameters can be `traded' for discontinuities in others. It is argued that, in general, in such cases extra domain-speci c information will be necessary in order to eliminate anomalous models of
23103290
The Event Calculus in Classical Logic - Alternative Axiomatisations
991675
A Simple Declarative Language for Describing Narratives With Actions
Abstract We describe a simple declarative languageEfor describing the effects of a series of action occurrences within a narrative.Eis analogous to Gelfond and Lifschitz's LanguageAand its extensions, but is based on a different ontology. The semantics ofEis based on a simple characterisation of persistence which facilitates a modular approach to extending the expressivity of the language. Domain descriptions inAcan be translated to equivalent theories inE. We show how, in the context of reasoning about actions,E's narrative-based ontology may be exploited in order to characterise and synthesise two complementary notions of explanation. According to the first notion, explanation may be partly modelled as the process of suitably extending an apparently inconsistent theory written inEso as to establish consistency, thus providing a natural method, in many cases, to account for conflicting sets of information about the domain. According to the second notion, observations made at later times can sometimes be explained in terms of what is true at earlier times. This enables domains to be given an alternative characterisation in which knowledge arising from observations is appropriately separated from other aspects of the domain. We also describe howEdomains may be implemented as Event Calculus style logic programs, which facilitate automated reasoning both backwards and forwards in time, and which behave correctly even when the knowledge entailed by the domain description is incomplete.
12976067
Reasoning about Discontinuities in the Event Calculus
This paper describes a logic-based formalism which combines techniques for reasoning about actions with standard mathematical techniques for modelling dynamic systems using the diierential calculus. The formalism inherits a robust solution to the frame problem which can handle con-currency, non-determinism, domain constraints and narrative. It also incorporates a mechanism for reasoning about the boundary conditions associated with systems of diier-ential equations deened over various intervals. This mechanism overcomes a number of drawbacks of previous systems .
28952345
Consistency enforcement in medical knowledge base construction
Some aspects of knowledge base creation can be partially or completely automated, resulting in higher quality and smaller effort. Computer assistance is particularly valuable in ensuring the internal consistency of a knowledge base. The article describes several techniques for consistency enforcement in QMR-KAT, an interactive knowledge base editor for the INTERNIST-I/QMR medical knowledge base. Two strategies that improve consistency are applicable to a wide range of situations. The first strategy prevents simple (but common) inconsistencies. The second strategy reveals facts that are potentially (but not necessarily) inconsistent with known data, and may require further evaluation. Both strategies use the contents of the existing knowledge base in the evaluation of new facts.
5731309
Synchronizing clipboards of multiple computers
This paper describes a new technique for transferring data between computers, the synchronized clipboard. Multiple computers can share a synchronized clipboard for all clipboard operations, so that data copied to the clipboard from one computer, using the standard Copy command, can be pasted directly on another computer using the standard Paste command. Synchronized clipboards are well-suited for a single user moving data among several computers in close proximity. We describe an implementation of synchronized clipboards that works across a wide range of existing systems, including 3Com PalmPilots, Microsoft Windows PCs, Unix workstations, and other Java-capable platforms. Our implementation adds no noticeable overhead to local copy and paste operations.
9330046
User interface continuations
Dialog boxes that collect parameters for commands often create ephemeral, unnatural interruptions of a program's normal execution flow, encouraging the user to complete the dialog box as quickly as possible in order for the program to process that command. In this paper we examine the idea of turning the act of collecting parameters from a user into a first class object called a user interface continuation. Programs can create user interface continuations by specifying what information is to be collected from the user and supplying a callback (i.e., a continuation) to be notified with the collected information. A partially completed user interface continuation can be saved as a new command, much as currying and partially evaluating a function with a set of parameters produces a new function. Furthermore, user interface continuations, like other continuation-passing paradigms, can be used to allow program execution to continue uninterrupted while the user determines a command's parameters at his or her leisure.
5333493
A Heuristic Approach to the Multiple Diagnoses Problem
A new heuristic model for the diagnosis of multiple related disorders in a patient case is presented. The model constructs differential diagnoses of single and related disorders, based on a medical knowledge base containing disease descriptions and linkages among diseases in the knowledge base.
5593182
Representing and querying data transformations
Modern information systems often store data that has been transformed and integrated from a variety of sources. This integration may obscure the original source semantics of data items. For many tasks, it is important to be able to determine not only where data items originated, but also why they appear in the integration as they do and through what transformation they were derived. This problem is known as data provenance. In this work, we consider data provenance at the schema and mapping level. In particular, we consider how to answer questions such as "what schema elements in the source(s) contributed to this value", or "through what transformations or mappings was this value derived?" Towards this end, we elevate schemas and mappings to first-class citizens that are stored in a repository and are associated with the actual data values. An extended query language, called MXQL, is also developed that allows meta-data to be queried as regular data and we describe its implementation scenario.