F. Barbic and B. Pernici. Time Modeling in Office Information Systems. In Proc. ACM SIGMOD Int'l. Conf. on Management of Data, pages 51--62, May 1985.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....information is usually specified according to a varying time scale [Flo91] For example, vegetation fluctuates according to a seasonal cycle, while temperature varies daily. office information systems Gamma temporal information is available in different time units of the Gregorian calendar [BP85,CR88,MPB92] For example, employee wages are usually recorded in the time unit of hours while the history of sales are categorized according to months. Design Space. A calendar is composed of an origin, a set of calendric granularities, and a set of conversion functions. The origin marks the ....

F. Barbic and B. Pernici. Time Modeling in Office Information Systems. In Proc. ACM SIGMOD Int'l. Conf. on Management of Data, pages 51--62, May 1985.

....for the support of temporal entities. For example, in a university information system multiple time units need to be supported. These include day, week, semester, etc; in office information systems temporal information is usually available in different time units of the Gregorian calendar [BP85] in real time systems a process is usually composed of sub processes that evolve according to different time scales [CMR91] in financial trading multiple calendars with different time units and operations need to be available to capture the semantics of financial data [CS93, CSS94] Therefore, ....

....database research community towards comprehensively modeling the basic temporal entities. The few works that 2 Citation Calendar(s) Granularities Time primitives Granularity conversions [CR87] No support Multiple Anchored Anchored [WJL91] WJS93] No support Multiple Anchored Anchored [BP85] MPB92] No support Multiple Anchored Anchored [MMCR92] No support Multiple Anchored Anchored [Sno95b] Multiple Multiple Anchored Unanchored Anchored Table 1: Temporal models supporting calendars and or granularities have appeared in this area have concentrated mainly on modeling anchored ....

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F. Barbic and B. Pernici. Time Modeling in Office Information Systems. In Proc. ACM SIGMOD Int'l. Conf. on Management of Data, pages 51--62, Austin, Texas, May 1985.

....the finer granularity [Clifford Rao 1987, Sarda 1993, Wiederhold et al. 1991] If the two granularities are incomparable (neither is finer than the other) then perform the operation to a granularity finer than both arguments. Coarser semantics Perform the operation to the coarser granularity [Barbic Pernici 1985, Montanari et al. 1992] For incomparable granularities, perform the operation to a granularity that is minimally coarser. This approach avoids adding indeterminacy not already present, but is, in some sense, the most conservative possibility, as information at the finer granularity is discarded. ....

....granularities) can be converted to other time units semi automatically via user provided conversion functions. Barbic and Pernici discuss relative, absolute, periodic, and imprecise times at different Gregorian granularities for office information systems in the context of constraint triggers [Barbic Pernici 1985]. They recommend converting operands to the coarsest granularity during a temporal (comparison) operation to avoid creating information. Barbic and Pernici also advocate a signed integer timestamp format which is the gist of our format. Montanari et al. investigate a slightly different problem, ....

Barbic, F. and B. Pernici. "Time Modeling in Office Information Systems," in Proceedings of ACM SIGMOD International Conference on Management of Data. Ed. S. Navathe. Association for Computing Machinery. Austin, TX: May 1985, pp. 51--62.

....by several novel applications where temporal constraints together with infinite and or indefinite temporal information play an important role. These applications include planning [3] scheduling [21] medical expert systems [18] geographical information systems [5] office information systems [4] and natural language processing systems [48] The organization of this paper is as follows. In the following section, we first discuss our assumptions about time and define our terminology. Then the basic features of temporal relations, generalized temporal relations and temporal tables are ....

F. Barbic and B. Pernici. Time Modeling in Office Information Systems. In Proceedings of the ACM SIGMOD International Conference on Management of Data, pages 51--62, 1985.

....we only know that it is located sometime during a 1440 minute period. ffl Perform the operation to the coarser granularity. This approach avoids adding indeterminacy not already present, but is in some sense the most conservative possibility, as information at the finer granularity is discarded [BP85, MMCR92] We can show that all these semantics (save generating an error) rest on operations that move times within the granularity graph. In all the proposed semantics the operands are first converted to the same granularity, and then the operation is carried out. Below we describe operations ....

....finer granularity semantics, with g 0 = is employed, with explicit cast or scale operations not permitted. Barbic and Pernici discuss relative, absolute, periodic, and imprecise times at different Gregorian granularities for office information systems in the context of constraint triggers [BP85] They recommend converting operands to the coarsest granularity during a temporal (comparison) operation to avoid creating information. Barbic and Pernici also advocate a signed integer timestamp format which is the gist of our format. Montanari et al. investigated a slightly different ....

F. Barbic and B. Pernici. Time Modeling in Office Information Systems. In S. Navathe, editor, Proceedings of ACM SIGMOD International Conference on Management of Data, pages 51--62, Austin, TX, May 1985. Association for Computing Machinery.

....of unrestricted (i.e. finite or infinite) definite information. However, indefinite information is also important in many temporal applications e.g. planning and scheduling [AKP91, SFG85] medical expert systems [Dut88] geographical information systems [BFAT91] office information systems [BP85] and natural language processing systems [MS88b] Motivated by these practical considerations, we develop the model of indefinite constraint databases by integrating the constraint database model of [KKR90] and the conditional table model of [IL84, Gra89] Our contributions to the theory of ....

F. Barbic and B. Pernici. Time Modeling in Office Information Systems. In Proceedings of the ACM SIGMOD International Conference on Management of Data, pages 51--62, 1985.

....temporal abstraction [181, 182] that uses artificial intelligence techniques to perform more sophisticated analyses of temporal relationships and intervals, generally with much lower query processing efficiency. Also not included are knowledge representation languages, such as Telos [149] or TSOS [15], which, while supporting either valid or transaction time, or both, are not strictly object oriented query languages. We first examine user defined time, as it is the most straightforward aspect of time to support, in both the data model and in the query language. Subsequent sections consider ....

Barbic, F., and Pernici, B.. "Time modeling in office information systems," In S. Navathe, editor, Proceedings of the ACM International Conference on Management of Data, Austin, TX, pp. 51--62, May 1985.

....time units to provide access to temporal relations. Additionally, they provide semantics for moving up and down a granularity lattice. Once again, our work encompasses their approach in that we show how we can convert one granularity to another, and how this leads to temporal indeterminacy. In [BP85] the issues of absolute, relative, imprecise and periodic times are discussed. Multiple granularities are supported for each time. Operands in operations involving mixed granularities are converted to the coarser granularity to avoid indeterminacy. In a more recent work [MPB92] the existence of ....

F. Barbic and B. Pernici. Time Modeling in Office Information Systems. In Proc. ACM SIGMOD Int'l. Conf. on Management of Data, pages 51--62, Austin, Texas, May 1985.

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