Ladkin, R (1986). Primitives and Units for Time Specification. In National Conference on Artificial Intelligence, pages 354-359.  Home/Search   Document Not in Database   Summary   Related Articles   Check

..... also important. 73(ippecl in tnls tutorial Nonlinear temporal domains: branching time has potential database applications in versioning and workflows [Attie et al. 1993] proposals too preliminary Multiple time granularities: important practical issue many possible approaches [Ladkin, 1986, Wang et al. 1993, Bettini et al. 1995] x MUltiple temporal almenslons To model multiple kinds of time: valid time vs. transaction time To represent intervals using pairs of points. To represent multiple temporal attributes in query results. Data models Query languages Expressive ....

Ladkin, R (1986). Primitives and Units for Time Specification. In National Conference on Artificial Intelligence, pages 354-359.

....0 ; s 1 ) 2 F k s 1 j= f ffl F k g #f8F j 2 F j(s 0 ; s 1 ) 2 F j ffl F j g = y Real time failure rates are represented in PCTL by linking all state transitions to a clock, 8i(s i ; s i 1 ) 2 F . Ladkin has developed similar techniques for grounding Allen s convex interval logic in real time [14]. ....

P. Ladkin. Primitives and units for time specifications. In T. Kehler, S.Rosenschein, R. Filman, and P.F. Patel-Schneider, editors, Proceedings Of The Fifth Annual Conference On Artificial Intelligence, pages 354--359. Morgan Kaufman, Los Altos, United States of America, 1986.

....; s 1 ) 2 F k s 1 j= f ffl F k g #f8F j 2 F j (s 0 ; s 1 ) 2 F j ffl F j g = y Real time failure rates are represented in PCTL by linking all state transitions to a clock, 8 i (s i ; s i 1 ) 2 F . Ladkin has developed similar techniques for grounding Allen s convex interval logic in real time [18]. 23 ....

P. Ladkin. Primitives and units for time specifications. In T. Kehler, S.Rosenschein, R. Filman, and P.F. Patel-Schneider, editors, Proceedings Of The Fifth Annual Conference On Artificial Intelligence, pages 354--359. Morgan Kaufman, Los Altos, United States of America, 1986.

....been ordered. In the case where the intervals are strictly ordered, the duration of an n interval I is simply the sum of the durations of its elements, i.e. X 1in I i Gamma I Gamma i . If elements can overlap, duration can be calculated by first convexifying the overlapping elements (Ladkin 1986); this means determining the shortest convex interval which spans all the overlapping elements. Alternatively, the interest may be in the mean (average) duration of the set of intervals. Finally, the extent of an n interval I = fhI Gamma 1 ; I 1 i; hI Gamma n ; I n ig is I ....

Ladkin, P.B. 1986. Primitives and Units for Time Specification. In Proceedings of AAAI-86, (San Mateo:Morgan Kaufman), 354-359.

....while intervals are defined as pairs of points. The last of the above assumptions is rather unnatural in any practical setting where conventional time units are needed. It is possible to start with this abstract model of time and develop a conventional system of time units as Ladkin did in [39, 40]. Ladkin defined a time unit system (TUS) which is a natural representation of everyday time on any scale. The basic units in Ladkin s TUS are sequences of the form [year; month; day; hour; where year; month; day; hour; are integers constrained appropriately. For example, the interval ....

Peter Ladkin. Primitives and Units for Time Specification. In Proceedings of AAAI-86, pages 354--359, 1986.

....model (Sarda, 13] emphasizes the fact that processing temporal queries can be viewed as a specialization of relational algebra query operations such as select and join. Finally, the work of Goodwin et al. 7] is relevant in the characterization of cumulative relations, and the work of Ladkin [9] provides a discussion of what was here described as collective relations. There are two important areas of temporal relational data processing not explored in this paper: handling uncertain information, and infinite databases. The first problem is addressed by extending the data model to include ....

Ladkin, P.B. 1986. Primitives and Units for Time Specification. In Proceedings of AAAI-86, (San Mateo:Morgan Kaufman), 354-359.

.... intervals and applying structural assumptions about time within the cluster in order to reduce the amount of processing required by the reasoner, is reminiscent of the notion of a reference interval, first introduced by Allen in [ Allen, 1983 ] The work of Ligozat [ Ligozat, 1991 ] and Ladkin [ Ladkin, 1986 ] on generalized intervals inspired many features of the approach to repeating event representation taken in this paper. 5 Summary This paper has presented a formulation of repeating events within the CSP framework. In reasoning about repeating events there is the need to manipulate indefinite ....

Ladkin, P. B. Primitives and Units for Time Specification. Proceedings of AAAI-86, (San Mateo:Morgan Kaufman), 354-359, 1986.

....(points and interval) and manipulated these constraints to implement operations that extend those in the relational algebra of databases. However, he does not use symbolic time that refers to an underlying calendar, nor does he discuss the integration of multiple calendars. Calendars: Ladkin [19, 20] uses sequences of integers to represent standard units assuming a linear hierarchy of time units, year, month, day, minutes etc. He uses this simple time system to define intervals. In our framework, intervals can be easily represented by simple constraints such as hlower boundi t hupper ....

P. Ladkin. (1986) Primitives and units for time specification, Proceedings of the Fifth National Conference on Artificial Intelligence (AAAI-86), Vol. 1, pps 354--359, Philadelphia, Pennsylvania, Morgan Kaufmann.

....Objects Numerical objects can include numbers, lists of numbers, ranges, and functions. These can be instantiations of planning variables or values of constraints posted by either the user or the system. Lists of numbers are provided for temporal reasoning along the lines of Ladkin s TUS syntax [4]. The following two global variables control the reasoning about lists of numbers. They can be set by using the Numerical command in the Profile menu, which brings up the menu shown in Figure 17.1. Figure 17.1: Menu for Numerical Profile numerical template [Variable] The value of this variable ....

P. B. Ladkin. Primitives and units for time specification. In Proceedings of the 1986 National Conference on Artificial Intelligence, pages 354--359, American Association for Artificial Intelligence, Menlo Park, CA, 1986.

.... or without the 6= relation) computing the minimal PA network and finding a solution of a PA network or its corresponding interval network [vB89a, vBC90, vB90b, vB92] These (and other) problems have also been discussed in by Ladkin and Maddux in [LM88a, LM88b, Lad87b, Lad87c, Lad87d, Lad87a, Lad86a, Lad86b] Finally, Len Schubert and his colleagues have implemented really practical algorithms for reasoning in PA networks as part of their natural language understanding system [MS88a, MS88b, MS90, GS93, GSS93] The work of [GA89] has also addressed similar implementation issues. Dechter, ....

Peter Ladkin. Primitives and Units for Time Specification. In Proceedings of AAAI-86, pages 354--359, 1986.

....available, one would never make incorrect choices. This is the physical mechanism used by tcs to implement hindsight. 2. 3 Relation to Other Work Major work in AI has focused on defining relationships between differing time intervals and creating a calculus for the manipulation of these relations [1, 2, 3, 14, 15], the use of constraint propagation techniques to narrow ambiguous bounds on temporal statements [13, 17] Tcs does not examine these issues. Instead, it assumes that the time data is available and the extent of any periods of validity can be calculated exactly. Medical applications have included ....

Peter Ladkin. Primitives and units for time specification. In Proceedings of the National Conference on Artificial Intelligence, pages 354--359. American Association for Artificial Intelligence, 1986.

....of its syntax [108] leaves some doubts whether the TSQL2 query language is well matched with the data model. In particular, TSQL2 designers still use the set of interval relationships of [5] For unions of intervals this set is not sufficient and should be augmented, e.g. along the lines of [80, 81, 83]. 5.3 HRDM HRDM (Historical Relational Data Model) 28, 29] based on some earlier foundational work [33, 32] is one of the most influential temporal data models. A similar model was proposed in [51, 52] HRDM supports a single, discrete, and infinite temporal domain, and a single time ....

P. Ladkin. Primitives and Units for Time Specification. In National Conference on Artificial Intelligence, pages 354--359, 1986.

....function that maps a utility function and a cache size into a new utility function. For a reaction to an event with n numeric parameters, a reaction interval is defined as an n dimensional region of parameter space over which the reaction is defined, bounded in each dimension by a convex interval (Ladkin 1986) (a continuous interval without holes) More precisely, for a reaction r e and parameters x 1 ; xn , if r e is defined over the region described by x i 2 [x s i ; x e i ] then that region is a reaction interval of r e . We will refer to the total utility of a reaction interval as the ....

Ladkin, P. 1986. Primitives and units for time specification.

.... Databases 5 2 Skipped in this tutorial Nonlinear temporal domains: ffl branching time has potential database applications in versioning and workflows [Attie et al. 1993] ffl proposals too preliminary Multiple time granularities: ffl important practical issue ffl many possible approaches [Ladkin, 1986, Wang et al. 1993, Bettini et al. 1995] BRICS Mini course on Temporal Databases 6 2 Multiple temporal dimensions To model multiple kinds of time: ffl valid time vs. transaction time To represent intervals using pairs of points. To represent multiple temporal attributes in query results. ....

Ladkin, P. (1986). Primitives and Units for Time Specification. In National Conference on Artificial Intelligence, pages 354--359.

....which consist of separate, convex interval components (Sections 2 and 2.1) We use the term unionof convex interval in this paper for intervals with a finite number of components only. We use the TUS (Time Unit System) notation for union of convex intervals over the rational numbers from [Lad86a, Lad87a] Sections 2.3, 4, and 4.1) and use it to describe algorithms for the useful interval combining operations of conglomeration (similar to union) and intersection (Section 3.1, Figures 1 and 2) Conglomeration is a partial operation on convex intervals, but is total on union of convex ....

.... sort of logical interdefinability one considers, and what sorts of mathematical objects one believes exist) Truth over explicit convex intervals and related structures has been studied in [Ham71, Hum79, McD82, All83, All84, BL89, vB92b] modal logics using intervals in [HS91, Ven92] and [Lad86a, Lad86b, MAK91, MSK93] have studied propositions and reasoning over unionof convex intervals; Lig90, Lig91] has further studied the mathematics of representations of convex intervals as sequences of points of varying length. 2.1 Choosing a Representation If we want to evaluate the truth of ....

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Peter B. Ladkin. Primitives and units for time specification. In Proceedings of the 5th National Conference on Artificial Intelligence (AAAI-86), pages 354--359. Morgan Kaufmann, 1986.

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Lad86.2 : Ladkin, P.B., Primitives and Units for Time Specification, Proceedings of AAAI-86, 354-359, Morgan Kaufmann, 1986.

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Ladkin, P. Primitives and Units for Time Specification. In Proc. of the AAAI-86, pages 354-359, 1986b.

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Ladkin, P.B. 1986. Primitives and Units for Time Specification. In Proceedings of AAAI-86, (San Mateo:Morgan Kaufman), 354-359.

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Peter Ladkin. Primitives and units for time specification. In AAAI '86 [ 1986 ] .

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