T. Cheng and S. Gadia. An Object-Oriented Model for Temporal Databases. In Proc. of the Int'l Workshop on an Infrastructure for Temporal Databases, 1993. 65  Home/Search   Document Not in Database   Summary   Related Articles   Check

....third direction deals with mechanisms supporting a selective recording of past values of properties, according to the truth value of conditions associated Immutable attributes can be regarded as a particular case of temporal ones, since their value is a constant function from a temporal domain. [7] [8] 9] 10] 11] 15] 18] 14] Ours o o data Oodaplex generic Tigukat MAD generic OSAM Oodaplex OM ODMG model time linear linear user def. linear linear linear user def. linear linear structure discrete discrete discrete discrete discrete discrete discrete time valid valid valid valid ....

T. Cheng and S. Gadia. An Object-Oriented Model for Temporal Databases. In Proc. of the Int'l Workshop on an Infrastructure for Temporal Databases, 1993. 65

....the prototype development. Section 6 concludes the paper and sketches future work. 2 Related work In the object oriented approaches (see [20] for a survey) temporal dimensions can be defined at the object level (e.g. TMAD [14] OSAM T [22] or at the attribute level (e.g. TOOSQL [16] OOTempSQL [6], TF ORM [10] T Chimera [2] or at both levels (e.g. TIGUKAT [12] OODAPLEX [26] Some of these studies support only a single time dimension (valid or transaction time) others support bitemporal time. Depending of the system, timestamp values may be instants, intervals or instant sets, and ....

T.S. Chang and S.K. Gadia. An object-oriented model for temporal databases. In Snodgrass [19].

....this framework. The final objective is to use the framework to analyze and compare the different temporal object models based on the design dimensions. In particular, the [RS91,SC91,KS92,PM92,CITB92,BFG97] temporal object models are considered. The work of Wuu Dayal [WD92] and Cheng Gadia [CG93] which follows a similar methodology as [WD92] are not considered since they do not provide concrete notions of time in their models. Object models which support versioning using time [KGBW90,WLH90,SRH90,Sci94] usually follow a structural embedding of temporality within type definitions. Thus, ....

T.S. Cheng and S.K. Gadia. An Object-Oriented Model for Temporal Databases. In Proceedings of the International Workshop on an Infrastructure for Temporal Databases, pages N1--N19, June 1993.

....temporal characteristics of the model and consider rather poor (simple) object models. 2 1 2 2 1 2 valid transaction temporal immutable non temporal migration oo data time time values class model structure dimension objects features [21] OODAPLEX user defined arbitrary objects NO [6] OODAPLEX linear valid objects NO [11] TIGUKAT user defined valid objects NO [13] MAD linear valid objects NO [19] OSAM linear valid objects NO [15] 3DIS linear valid objects NO [7] generic linear valid objects NO Our model Chimera linear valid both YES Legenda: One single time dimension ....

....valid objects NO [15] 3DIS linear valid objects NO [7] generic linear valid objects NO Our model Chimera linear valid both YES Legenda: One single time dimension is considered, but it can be interpreted either as transaction or as valid time. OODAPLEX supports metadata, but neither [21] nor [6] consider them. Table 1: Comparison among the existing temporal object oriented data models (I) Concerning the temporal aspects, we identify the time domain considered by each approach. In particular, we consider time structure and time dimension [17] Most models support a linear discrete time ....

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T. Cheng and S. Gadia. An Object-Oriented Model for Temporal Databases. In , 1993.

....a list of the calendric elements in a time instant. For example, B calElements applied to the instant June 15, 1995 returns the list (414; 6; 15) 6 Related Work Although there have been a substantial number of proposals on adding time to object models [RS91, RS93, KS92, WD92, DW92, SC93, CG93] it is quite surprising to note that none of them provides comprehensive support for modeling multiple calendars and handling multiple granularities. Most of these models assume the presence of an underlying calendar (usually Gregorian) which has 32 T instant B less: T instant T boolean B ....

T.S. Cheng and S.K. Gadia. An Object-Oriented Model for Temporal Databases. In Proceedings of the International Workshop on an Infrastructure for Temporal Databases, pages N1--N19, Arlington, Texas, June 1993. 35

....in a natural way complex objects and relationships can be extended to the modelling of temporal information. Two different approaches to model temporal information in object oriented database systems have been proposed [25] the attribute timestamping approach associates time to object attributes [10, 11, 24], whereas the object versioning approach associates time to the whole object [20, 27, 29] However, few of the proposed models have been actually implemented [20, 23, 27] In this report we propose and compare two possible approaches to implement temporal objectoriented data models, based on the ....

....by specializing, that is, refining, the domain of the attribute with respect to the notions of covariance rule for result parameters and contravariance rule for the input ones. The main idea is that attribute domains can be replaced in subclasses by refined types. This means that, as suggested in [10], a non temporal attribute can be refined in a temporal attribute (on the same domain or on a most specific one) but not vice versa. In C , each subclass must contain all attributes and operations of all its superclasses but the possibility of refining an attribute domain is not supported. In ....

T. Cheng and S. Gadia. An Object-Oriented Model for Temporal Databases. In Proc. of the Int'l Workshop on an Infrastrutcture for Temporal Databases, 1993.

....object oriented SQL [RS93b] ffl The OSAM T model model and its associated query language called OQL T [SC91, SKL89] is based on notion of time varying association. ffl The OODAPLEX model [DW92, WD93] accommodates temporal data modeling through the notion of function. ffl The OOTempDBM model [CG93] captures the temporal semantics of objects through type inheritance. ffl The [KRS90] extends a complex object model by adding transaction and valid times to tuples. ffl The TIGUKAT [GO93] model incorporates time as an abstract type. TIGUKAT models everything in the system as a first class ....

T.S. Cheng and S.K. Gadia. An Object-Oriented Model for Temporal Databases. In Proceedings of the International Workshop on an Infrastructure for Temporal Databases, Arlington, TX, June 1993.

....of (relative and absolute) keys. Finally, some models keep track of the dynamic links between an object and its most specific class. Indeed, an important dynamic aspect of object oriented databases is that an object can dynamically change type, by specializing or generalizing its current one. [7] [8] 9] 10] 11] 15] 18] 14] Ours o o data Oodaplex generic Tigukat MAD generic OSAM Oodaplex OM ODMG model time linear linear user def. linear linear linear user def. linear linear structure discrete discrete discrete discrete discrete discrete discrete time valid valid valid valid valid ....

T. Cheng and S. Gadia. An Object-Oriented Model for Temporal Databases. In Proc. of the Int'l Workshop on an Infrastructure for Temporal Databases, 1993.

....leaves more opportunities for optimization or whether it is more userfriendly. We believe that their approach is not well suited to version control, since version control inherently requires to associate one time interval with a version. Another temporal OODB model is proposed by Cheng and Gadia [3]. Their temporal OODB language, called TempSQL, is based on temporal expressions, which map boolean predicates to temporal domains. For example, the temporal expression [ e.salary 15K] returns the time period (lifespan) in which the salary of the employee e was greater than 15K. Such temporal ....

T. S. Cheng and S. K. Gadia. An Object-Oriented Model for Temporal Databases. In R. T. Snodgrass, editor, Proceedings of the International Workshop on an Infrastructure for Temporal Databases, Arlington, TX, June 1993.

....but objects in general, which includes things such as code in addition to data. reasonably conclude that he died sometime between 5 : 00am May 30 and 5 : 59am May 30. There have been many object oriented temporal model proposals (see, for example, KC86, RS91, RS93, KS92, DW92, WD92, SC93, CG93] These models differ in the functionality that they offer, but none of them provides support for uniformly handling different domains of time, granularities and indeterminate temporal information. In this paper we describe a temporal object model which is sufficiently powerful to meet the ....

....T discreteDeterminateInterval T discreteIndeterminateInterval T discreteInstant T discreteDeterminateInstant T discreteIndeterminateInstant T specialInterval T span T discreteSpan T granularity Figure 8: The complete time type hierarchy. KC86, RS91, RS93, KS92, WD92, DW92, SC93, CG93] none of them provides support for handling both the continuous and discrete time domains, multiple granularities and indeterminate temporal information. In the context of OBMSs, KC86] describes a model to handle complex objects and discusses the representation and temporal dimensions to ....

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T.S. Cheng and S.K. Gadia. An Object-Oriented Model for Temporal Databases. In Proceedings of the International Workshop on an Infrastructure for Temporal Databases, pages N1--N19, Arlington, Texas, June 1993.

....statically verified. To best of our knowledge, this is the first extensive investigation concerning navigational accesses in a temporal context and addressing the problem of a static analysis of path expressions. One of the few papers considering navigational access is the one by Cheng and Gadia [7]. Their language OOTempSQL provides a sublanguage for associative navigation relying on notions very similar to our concept of temporal expression. However, neither a formal semantics is given for the language nor correctness conditions have been stated. The remainder of the paper is organized as ....

.... a path expression under oid assignment , denoted as [ is recursively defined as follows: if , that is, it is the oid assigned to variable by ; if , if is an instant valued temporal expression, and ( 0( if 7 2 , [ 7 ]] if 7 2 , 7 ] if is a temporal expression, if is a temporal expression, 7 f dom f f 7 1 1 2 2 1 1 1 1 2 2 1 1 4.3 Correctness 4 T IME2T IME fl 0 0 0 0 # # # # # # # # # n n n i i i # ....

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T. Cheng and S. Gadia. An Object-Oriented Model for Temporal Databases. In , 1993.

....Special Issue on Time Oriented Systems in Medicine The number of patients in treatmentA is the cardinality of the collection returned as a result of the treatmentA.B patients behavior application. 2 5 Related Work There have been many object oriented temporal model proposals (see, for example, [20, 24, 25, 17, 29, 12, 3, 28, 2]) These models differ in the functionality that they offer, but none of them provide support for all the requirements of a pharmacoeconomics medical trial. More specifically, in our model: ffl Both linear and branching orders are supported. The above temporal ODBMSs support only linear time. As ....

T.S. Cheng and S.K. Gadia. An Object-Oriented Model for Temporal Databases. In Proceedings of the International Workshop on an Infrastructure for Temporal Databases, pages N1--N19, Arlington, Texas, June 1993. Also published as Technical Report TR-93-05.

....object, class, etc. Still, these concepts capture characteristics that we intuitively would expect an object model to support. Thereby, making the dioeerent models comparable. 2.2. 1 Temporal Extensible Object Models Wuu and Dayal s extensions to OODAPLEX [94, 95] Cheng and Gadia s OOTempDBM [15] (also based on OODAPLEX) and Goralwalla and #zsu s extensions to TIGUKAT [40, 66] are representatives of this class. We presents only Wuu and Dayal s model and compare it with the other two at the end of this section. 2.2.1.1 T OODAPLEX 8 T OODAPLEX is based on the object oriented data model ....

T. S. Cheng and S. K. Gadia. An Object-Oriented Model for Temporal Databases. In R. T. Snodgrass, editor, Proceedings of the International Workshop on an Infrastructure for Temporal Databases, pages N 119, Arlington, TX, June 1993.

....programs written in C . The first important contribution of this work is to demonstrate a concrete design and implementation scheme of a runnable temporal object database management system. Although a number of temporal persistent object models have been proposed in the research community [5, 7, 17, 18], little work has been reported on concrete design and implementation of underlying systems. Related works also include researches on version management in ODBMSs [1, 8, 10] In most ODBMSs, however, versions are created by specific operators designated for version derivation rather than by ....

T. S. Cheng and S. K. Gadia. An ObjectOriented Model for Temporal Database. In R. T. Snodgrass (editor), Proceedings of International Workshop on an Infrastructure for Temporal Databases, June 1993.

....well m:D=G well 1) S ; m:U=G well 1:0 ] b [ m:D=G well 1:5 ] b . 3.3 Path Expressions A path expression is an expression that allows one to navigate through aggregation hierarchies on objects. Navigational access to temporal objects has been investigated in OOTempSQL [4], and revisited in [2] The notion of path expression we propose here, besides being generalized to a multidimensional context, actually combines and extends the two notions. In particular, we distinguish among simple path expressions (inspired by [4] that navigate through the object aggregation ....

....objects has been investigated in OOTempSQL [4] and revisited in [2] The notion of path expression we propose here, besides being generalized to a multidimensional context, actually combines and extends the two notions. In particular, we distinguish among simple path expressions (inspired by [4]) that navigate through the object aggregation hierarchy, aligning the dimensions of the traversed objects; qualified path expressions (inspired by [2] in which the portion of the dimensional space one is interested in navigating can be restricted; and single valued 4 S is a shorthand for ....

T. S. Cheng and S. K. Gadia. An Object-Oriented Model for Temporal Databases. In Proc. of the Int'l Workshop on an Infrastructure for Temporal Databases, 1993.

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