Proceedings Ninth International Symposium on Temporal Representation and Reasoning

We propose an efficient operational semantics for a new class of rewrite systems, namely timed rewrite systems. This class constitute a conservative extension of first-order conditional term rewrite systems together with time features such as clocks, signals, timed terms, timed atoms and timed rules. We define first timed rewrite systems and illustrate them through some examples. A naive approach to the operational semantics is very costly in space. We propose, for a large class of programs, an improved calculus with a linear space complexity. Finally, we show how our framework compares to related work.

We propose a logical approach to represent and reason about different time granularities. We identify a time granularity as a discrete infinite sequence of time points properly labelled with proposition symbols marking the starting and ending points of the corresponding granules, and we intensively model sets of granularities with linear time logic formulas. Some real-world granularities are provided to motivate and exemplify our approach. The proposed framework permits to algorithmically solve the consistency, the equivalence, and the classification problems in a uniform way, by reducing them to the validity problem for the considered linear time logic.

Event notification services are used in various applications such as digital libraries, stock tickers, traffic control, or facility management. However to our knowledge, a common semantics of events in event notification services has not been defined so far. We propose a parameterized event algebra which describes the semantics of composite events for event notification systems. The parameters serve as a basis for flexible handling of duplicates in both primitive and composite events.

Chúng tôi giới thiệu một logic thời gian để lý luận về các ứng dụng toàn cầu. Trước tiên, chúng tôi định nghĩa một logic mô-đun cho địa phương tính, nhúng các lý thuyết địa phương của mỗi thành phần vào một lý thuyết về các trạng thái phân tán của hệ thống. Chúng tôi cung cấp cho logic một hệ thống tiên đề đầy đủ và chuyên sâu. Sau đó, chúng tôi mở rộng logic với một toán tử thời gian. Đóng góp của chúng tôi là khả năng lý luận về các tính chất liên quan đến nhiều thành phần theo cách tự nhiên, ngay cả khi không có đồng hồ toàn cầu, như được yêu cầu trong một môi trường bất đồng bộ.

A growing number of industrial applications use rule-based programming. Frequently, the implementation of the inference engine embedded in these applications is based on the RETE algorithm. Some applications supervise a flow of events in which time, through the occurrence dates of the events, plays an important role. These applications need to be able to recognize patterns involving events. However the RETE algorithm does not provide support for the expression of time-sensitive patterns. This paper proposes an extension of RETE through the concepts of time-stamped events and temporal constraints between events. This allows applications to write rules that process both facts and events.

Representing and reasoning with both temporal constraints between classes of events (e.g., between the types of actions needed to achieve a goal) and temporal constraints between instances of events (e.g., between the specific actions being executed) is a ubiquitous task in many areas of computer science, such as planning, workflow, guidelines and protocol management. The temporal constraints between the classes of events must be inherited by the instances, and the consistency of both types of constraints must be checked. We propose a general-purpose domain-independent knowledge server dealing with these issues. In particular, we propose a formalism to represent temporal constraints, we show two algorithms to deal with inheritance and to perform temporal consistency checking, and we study the properties of the algorithms.

We present a method for formalising the behaviour of simple deterministic devices and protocols in a way that makes explicit the causal dependencies amongst the component elements, thereby allowing true causal (as opposed to purely temporal) reasoning. Our intention is to handle such systems effectively in the simplest possible way, without invoking additional problematic considerations (concerning, for example, non-monotonicity) that may be necessary for modelling a more general range of scenarios.

Summary form only given. Data expiration is an essential component of data warehousing solutions: whenever large amounts of data are repeatedly collected over a period of time, it is essential to have a clear approach to identifying parts of the data no-longer needed and a policy that allows disposing and/or archiving these parts of the data. Such policies are necessary even if adding storage to accommodate an ever-growing collection of data were possible, since the growing amount of data needs to be examined during querying and in turn leads to deterioration of query performance over time. The approaches to data expiration range from adhoc administrative policies or regulations to sophisticated data analysis-based techniques. The approaches have, however, one thing in common: intuitively, they try to identify the parts of the data collection that are not needed in the future. The key to deciding if a piece of information will be needed in the future lies in identifying what queries can be asked over the collection of data and how the collection can evolve from its current state. The various techniques proposed in the literature differ in the way they identify no longer needed parts of data. The author formalizes the notion of data expiration in terms of how the data is used to answer queries. He surveys existing approaches to the problem in a unified framework and discusses their features and limits and the limits of data expiration based techniques in general. Particular focus is on comparing the performance of various data expiration methods.

Simple partial logic (SPL) is, broadly speaking, an extensional logic which allows for the truth-value gap. First I give a system of propositional SPL by partializing classical logic, as well as extending it with several non-classical truth-functional operators. Second I show a way based on SPL to construct a system of tensed ontology, by representing tensed statements as two kinds of necessary statements in a linear model that consists of the present and future worlds. Finally I compare that way with other two ways based on Lukasiewicz's three-valued logic and branching temporal logic.

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