A. G. Walker. Dures et instants. Revue Scientifique, 85:131--134, 1947.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....but quickly turns to a di#erent method due to A. G. Walker. Walker was motivated by the same idea as Russell, that instants should not be postulated but constructed. He took as primitive for his construction a partially ordered (by the relation of complete precedence) set of events ( durees ) [24]. Both Walker and Russell use for their constructions a single (partial) event ordering which is possibly infinite. In this article Walker wants to show that the instants obtained from the partially ordered set form a complete linear order (that is, the temporal experience of an observer in ....

....obtained with Walker s construction. i 4 = e 1 , e 2 , e 3 , e 5 ) and of course, we have i 1 i 2 i 3 i 4 . There cannot be any other instant, otherwise it would have an empty past or future. Notice that the instants are traces of changes in the event structure. Lemma 1 (Walker [24], as modified by Thomason [20, p. 89] Every instant is completely determined by its past. That is, a) if W ; P, O, B, E is an event structure, and (P, C, F ) an instant, then (1) P is a nonempty proper subset of W (2) if #a # d) then d (3) if for all a P : E(a, d) then #b#a # ....

A. G. Walker. Durees et instants. Revue Scientifique, 85:131--134, 1947.

....a duration . with a rearward and forward looking end . The latter feature is absent from the construction of instant thus given. The reader may well wonder whether James description is at all consistent, but in fact a di#erent construction of instants from events has been proposed by Walker [17], a construction in which instants become directed even though they are indivisible. 1.3.2 Walker s construction Walker was a physicist interested in the foundations of relativity theory, in particular in the question where the real numbers that physics uses to represent time come from. Many ....

....if B and E are definable in terms of P , these predicates are included in the modified definition of event structure This is because this automatically gives the right definition of one event structure being a substructure of another, a matter of some importance in section 1.3.5. Lemma 1 (Walker [17], as modified by Thomason [14, p. 89] Every instant is completely determined by its past. That is, a) if W ; P, O, B, E is an event structure, and (P, C, F ) an instant, then 1. P is a nonempty proper subset of W 2. if PE(a, d) then d 3. if for all a P : E(a, d) then #b#a # P : ....

A. G. Walker. Durees et instants. Revue Scientifique, 85:131--134, 1947.

....reals. The question then is how to relate discrete computational actions, which by their nature have granularity, with well established physical theories of continuous time. However, this problem is not unique to computation and Whitrow [11] describes how from the work of Russell [9] and Walker [10] it is possible to obtain a continuous time domain from an appropriate definition of instants of time. A crucial aspect of this work is that time is defined in terms of actions, not conversely; this contrasts with the view so far taken in computational models, where actions are laid out in some ....

....a terminates (but the beginning of b may coincide with the termination of a) Two actions a and b overlap if a does not precede b and b does not precede a. The relation OE on ACT is irreflexive and antisymmetric. It is also assumed to satisfy the following condition, called Walker s postulate ([10, 11]) 8a; b; c; d 2 ACT : a OE b b c c OE d) a OE d) 3 where (overlaps) is a relation on ACT defined by 8a; b 2 ACT : a b , a OE b) b OE a) Note that is symmetric and reflexive, so Walker s postulate leads to the transitivity of OE and thus OE is a strict partial order on ....

A.G. Walker. Dur'ees et instants. Revue Scientifique, 85:131--134, 1947.

....than instants. One alternative are periodbased theories since periods are usually associated with events that take time . A further step in that direction is directly developing theories based on events. Periods Period based theories interested researchers in philosophy, linguistics and AI [54, 19, 39, 12, 2, 4]. For instance, Allen proposes a theory exclusively based on periods and the 13 relations between pairs of them shown in figure 3. This theory has been reformulated in terms of the sole relation Meets by Allen Hayes. See appendix B for details. Events Event based theories are motivated by the ....

A. Walker. Dur'ees et instants. Revue Scientifique, 85:131--134, 1948.

....One alternative are periodbased theories since periods are usually associated with events that take time . A further step in that direction is directly developing theories based on events. 4. 2 Period based Theories Period based theories interested researchers in philosophy, linguistics and AI [26, 9, 19, 7, 2, 4]. For instance, based on ideas from philosophy and linguistics, Allen [2] proposed a period based theory of time as a fundamental piece of a framework for reasoning about action and plans. Next we present Allen s proposal and futher results that take it as starting point. 4.2.1 Allen s Period ....

A. Walker. Dur'ees et instants. Revue Scientifique, 85:131--134, 1948.

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A. G. Walker. Dures et instants. Revue Scientifique, 85:131--134, 1947.

No context found.

A. G. Walker. Dures et instants. Revue Scientifique, 85:131--134, 1947.

No context found.

A. G. Walker. Dures et instants. Revue Scientifique, 85:131--134, 1947.

No context found.

A. G. Walker. Dures et instants. Revue Scientifique, 85:131--134, 1947.

No context found.

A. G. Walker. Dures et instants. Revue Scientifique, 85:131--134, 1947.

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