S. K. Gadia and C. S. Yeung. A Generalized Model for a Relational Temporal Database. In Proceedings of ACM SIGMOD, pages 251--259, Chicago, IL, June 1988.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....assumption. Formulas of epistemic modal logic cover all these different proof theoretic approaches. The algebraic background is reviewed in standard textbooks like [Bis95, DeA85, Mai83, PDG89] Ull89] and in the overview [Kan90] The extensions of the relational model are discussed also in [BCN92, ElN89, GaY88, JaS82, ScS90]. Distributed schemes [CeP84] can be defined by database schemata with a set of allocation constraints defined on a network. The general approach to integrity constraints is developed in [Tha91, Tha92] and uses extensions from [BCV86] 3 Algebraic and Structural Constraints 3.1 Identification ....

S.K. Gadia, C.-S. Yeung, A generalized model for a relational temporal database. Proc. ACM SIGMOD

....valid time, under this assumption, this data model supports degenerate bitemporal relations as well as general transaction time relations. Gadia presents a multi dimensional data model which is in turn restricted to a two dimensional data model with valid and transaction time as the dimensions [GY88] In this model, however, only data valid in the past may be stored. For example, it is impossible to store on May 11, 1995 the fact that Employee Kate will be in the Shipping department from September 1, 1995 until February 29, 2000. Therefore, the model does not support fully general ....

S. K. Gadia and C.-S. Yeung. A Generalized Model for a Relational Temporal Database. In Proceedings of the ACM SIGMOD '88, pages 251--259, 1988.

....valid time, under this assumption, this data model supports degenerate bitemporal relations as well as general transaction time relations. Gadia presents a multi dimensional data model which is in turn restricted to a two dimensional data model with valid and transaction time as the dimensions [GY88] In this model, however, only data valid in the past may be stored. For example, it is impossible to store on May 11, 1995 the fact that Employee Kate will be in the Shipping department from September 1, 1995 until February 29, 2000. Therefore, the model does not support fully general ....

S. K. Gadia and C.-S. Yeung. A Generalized Model for a Relational Temporal Database. In Proceedings of the ACM SIGMOD '88, pages 251--259, 1988. 45

....uses the timeslice operation. SELECT F1.NAME FROM EMP F1 WHERE F1 OVERLAP 1990 418 THE TSQL2 QUERY LANGUAGE FROMTIME 1:1:1990 TOTIME 12:31:1990 SELECT F1.NAME FROM EMP F1 2. 7 TempSQL Gadia s TempSQL is based on a N1NF relational temporal data model which is attribute value timestamped [6, 7, 8]. A tuple may have more than one value (timestamped) for each attribute, but the union of the timestamps in each attribute must be the same throughout the entire tuple, resulting in a homogeneous temporal relation. In their data model, they group a history of an entry into a tuple, instead of ....

Gadia, S. K. and C. S. Yeung. "A Generalized Model for a Relational Temporal Database," in Proceedings of ACM SIGMOD International Conference on Management of Data. Association for Computing Machinery. Chicago, IL: June 1988, pp. 251--259.

.... Ahn Temporally Oriented Data Model [27] valid Ariav Time Relational Model [6] both Ben Zvi [21] valid Brooks Historical Data Model [26] valid Clifford 1 Historical Relational Data Model [35] valid Clifford 2 Homogeneous Relational Model [12] valid Gadia 1 Heterogeneous Relational Model [41] valid Gadia 2 TempSQL [53] both Gadia 3 DM T [47] transaction Jensen LEGOL 2.0 [24] valid Jones DATA [45] transaction Kimball Temporal Relational Model [43] valid Lorentzos [50] both McKenzie Temporal Relational Model [16] valid Navathe HQL [29] valid Sadeghi HSQL [32] valid Sarda ....

....supports both valid and transaction time. Many of the criteria concerning transaction time that are satisfied by the data model discussed below 374 THE TSQL2 QUERY LANGUAGE are also satisfied by Bhargava s data model. Gadia 2 Gadia s multihomogeneous model [18] and Yeung s heterogeneous models [41, 42] are all extensions of the homogeneous model. They lift the restriction that all attribute values in a tuple be functions on the same temporal element, in part to be able to perform Cartesian product without loss of temporal information caused by merging two timestamps into one. We consider here ....

[Article contains additional citation context not shown here]

Gadia, S. K. and C. S. Yeung. "A Generalized Model for a Relational Temporal Database," in Proceedings of ACM SIGMOD International Conference on Management of Data. Association for Computing Machinery. Chicago, IL: June 1988, pp. 251--259.

.... # s,iffor all times t 1 not exceeding the current time and for all times t 2 , # V t 2 (# B t 1 (r) # V t 2 (# B t 1 (s) 2 The concept of snapshot equivalence is due to Gadia and was first defined for valid time relations [7] and was later generalized to multiple dimensions [8]. We have chosen not to use the original term weakly equivalent to avoid confusion with the different notions of weak equivalence over algebraic expressions (e.g. 33] and over data models [6] In the next section, we will discuss how snapshot equivalence may also be applied to pairs of ....

S. K. Gadia and C. S. Yeung. A Generalized Model for a Relational Temporal Database. In Proceedings of ACM SIGMOD, pages 251--259, 1988.

....in a tuple oriented relational data model. TEER does not add new syntactical constructs to the EER model; instead, it gives new meaning to the existing EER modeling constructs making them temporal. The Representation of Time The time representation is similar to that proposed by Gadia and Yeung [14] for the relational model, but is adapted to the requirements of the ER model. A time interval, denoted by [t 1 ,t 2 ] is defined to be a set of consecutive equidistant time 958 DATABASE DESIGN instants, where t 1 is the starting instant and t 2 the ending instant. The distance between two ....

S. K. Gadia and C. S. Yeung. A Generalized Model for a Relational Temporal Database. In Proceedings of ACM SIGMOD International Conference on Management of Data, pp. 251--259, June 1988.

....or conventional relations produces specialized temporal relations, as we shall see shortly. 4. 2 Retroactive Temporal Relations Gadia presents a multi dimensional temporal data model which is in turn restricted to a two dimensional data model with valid and transaction time as the dimensions [23]. In this model, however, only data valid in the past may be stored. For example, it is impossible to store on May 11, 1991 the fact that As of now, Dr. Jones is hired as an assistant professor from September 1, 1991 until August 31, 1997. Therefore, the model does not support fully general ....

S. K. Gadia and C.-S. Yeung. A Generalized Model for a Relational Temporal Database. In Proceedings of the ACM SIGMOD Conference, pages 251--259, 1988.

....valid time, under this assumption, this data model supports degenerate bitemporal relations as well as general transaction time relations. Gadia presents a multi dimensional data model which is in turn restricted to a two dimensional data model with valid and transaction time as the dimensions [16]. In this model, however, only data valid in the past may be stored. For example, it is impossible to store on May 11, 1995 the fact that Employee Kate will be in the Shipping department from September 1, 1995 until August 31, 1997. Therefore, the model does not support fully general bitemporal ....

S. K. Gadia and C.-S. Yeung. A Generalized Model for a Relational Temporal Database. In Proceedings of the ACM SIGMOD '88, pp. 251--259 (1988).

....world, but also its previous and possibly future states. Temporal languages must handle the temporal aspects of data accordingly. In recent years several temporal data models and languages have been developed. Examples for temporal relational data models and corresponding temporal languages are [1, 2,3,4,5,6,7,8,9]. Most of the temporal database languages are extensions of traditional textual database languages, e.g. SQL. Therefore the extended syntax and semantics of temporal languages is even harder to learn than for traditional (non temporal) languages. Users have to know the syntax and semantics of the ....

S. K. Gadia und C.-S. Yeung. A generalized model for a relational temporal database. In Proc. of the ACMSIGMOD 1988 International Conference on Management of Data, pp. 251-259, Chicago, 1988.

....should be available for the discovery process. As a variation to the model of database instances, tuples or attribute values with different timestamps can also be stored in the same relation and be associated with the same tuple identifiers. This is popularly practiced in temporal databases [10, 11]. However, different representations and storage structures influence only the method of retrieval but not the final learning result. Therefore, we assume that the changing data are stored in different database instances in this study, and the extraction of evolving data involves data retrieval ....

S. K. Gadia and C. S. Yeung. A generalized model for a relational temporal databases. In Proc. 1988 ACM-SIGMOD Int'l Conf. Management of Data, pages 251--259, Chicago, IL, 1988.

....of epistemic modal logic cover all these different proof theoretic approaches. Bibliographical remarks The algebraic background is reviewed in standard textbooks like [Bis95, DeA85, Mai83, PDG89] Ull89] and in the overview [Kan90] The extensions of the relational model are discussed also in [BCN92, ElN89, GaY88, JaS82, ScS90]. Distributed schemes [CeP84] can be defined by database schemata with a set of allocation constraints defined on a network. The general approach to integrity constraints is developed in [Tha91, Tha92] and uses extensions from [BCV86] 3 Algebraic and Structural Constraints 3.1 Identification and ....

S.K. Gadia, C.-S. Yeung, A generalized model for a relational temporal database. Proc. ACM SIGMOD 1988, June 1988, Chicago, p. 251-259.

....i.e. only data (facts) of the present are stored. Therefore no queries involving several tenses may be handled and it is not possible to adjust or modify previous states. Hence, no time manipulation commands (point 4 in section 3) and its relationship to consistency have to be considered. In [6] a refined (versus our approach) time concept (linear, multidimensional, having a start and an end point) is introduced. But no deduction rules or constraints were considered, thus the problem of consistency and deduction is not addressed. Each attribute of a predicate may strongly change (over ....

S.K.Gadia, C.Yeung, A Generalized Model for a Relational Temporal Database, in Proceedings of the ACM-SIGMOD International Conference on Management of Data, 1988.

....[Gad88] allows two types of objects: valid time elements [GV85] and valid time relations. Valid time elements, which were first proposed by Shashi Gadia, have the nice property that they are closed under union, difference, and complementation, unlike intervals. ffl Gadia s multihomogeneous model [GY88] is an extension of the homogeneous model. It lifts the restriction that all attribute values in a tuple be functions on the same temporal element, in part to be able to perform Cartesian product without loss of temporal information caused by merging two timestamps into one. In this data model, ....

S.K. Gadia and C.S. Yeung. A generalized model for a relational temporal database. In Proceedings of the ACM International Conference on Management of Data, pp. 251--259, Chicago, IL, June 1988.

....model is a challenging job and it raises many interesting questions. The following is a list of the most important ones: ffl What is the static model which will be extended So far, most of the work has concentrated on the relational data model [CW83, CT85, CC87, Gad86, Gad88, GV85, Sno87, MS87, GY88, GB89, LJ88a, LJ88b, SRH90, KSW90] some researchers have considered extending object oriented database models [Klo81, DBG 85, MBJK90, EWK93] or deductive database models [CI88, CI89, Cho90b, Cho90a, MPB92, Sri91] Wuu92, Wuu93] have chosen to use the available facilities of an ....

....[Wuu92, Wuu93] have chosen to use the available facilities of an object oriented model for modeling time. The advantage of this work is that no special constructs are needed in the query language. ffl What are the dimensions of time that will be supported [CW83, CT85, CC87, Gad86, Gad88, GV85, GY88, LJ88a, LJ88b, KSW90, EWK93, Cho90a] have considered only valid time while [SRH90, LS93b, LS93a] consider only transaction time. Sno87, MS87, GB89, MBJK90, MPB92, Sri91] considered both valid time and transaction time. ffl What is an appropriate ontology and structure for time In contrast ....

[Article contains additional citation context not shown here]

Sashi K. Gadia and Chuen-Sing Yeung. A Generalized Model For a Relational Temporal Database. In Proceedings of ACM SIGMOD International Conference on Management of Data, pages 251--259, 1988.

.... j s, if for all times t 1 not exceeding the current time and all times t 2 , V t 2 (ae B t 1 (r) V t 2 (ae B t 1 (s) ut The concept of snapshot equivalence is due to Gadia and was first defined for valid time relations [Gad86] and was later generalized to multiple dimensions [GY88] We have chosen to avoid the original term weakly equivalent to avoid confusion with the different notion of weak equivalence over algebraic expressions (e.g. Ull82] Disambiguating the original term by prefixing with temporally is awkward. In the next section, we will discuss how ....

S. K. Gadia and C. S. Yeung. A Generalized Model for a Relational Temporal Database. In Proceedings of ACM SIGMOD, pages 251--2259, 1988.

.... Data Model [14] both Ariav [17] valid Bassinouni [25] both Bhargava Bitemporal Conceptual Data Model [99] both BCDM Time Relational Model [21] both Ben Zvi DATA [113] transaction DATA DM T [92] transaction DM T Homogeneous Relational Model [64] valid Gadia 1 Heterogeneous Relational Model [66] valid Gadia 2 Historical Data Model [45] valid HDM Historical Relational Data Model [42] valid HRDM [101] valid Jones [137] transaction Lomet Temporal Relational Model [139] valid Lorentzos [140] valid Lum [145] both McKenzie Temporal Relational Model [150] valid Navathe [166] ....

Gadia, S.K., and Yeung, C.S., "A generalized model for a relational temporal database," in Proceedings of the ACM International Conference on Management of Data, pp. 251-- 259, Chicago, IL, June 1988.

....that the user defined time was treated just as a data type requiring only input output functions. However, as we shall show in section 3, the user defined time models another validity just as effective or registration based validity. Yet another confusion arises in the work of Gadia and Yeung [GY88] in which the valid and transaction times of [SA85] were adopted for the demonstration of their n dimensional, symmetric time concept. However, the valid and transaction times of [GY88] were in fact not those of [SA85] but the event and transaction times of [CM84] respectively. To summarize, ....

....just as effective or registration based validity. Yet another confusion arises in the work of Gadia and Yeung [GY88] in which the valid and transaction times of [SA85] were adopted for the demonstration of their n dimensional, symmetric time concept. However, the valid and transaction times of [GY88] were in fact not those of [SA85] but the event and transaction times of [CM84] respectively. To summarize, we identify several problems with the previous approaches. First, we think there has been a dichotomous classification of time concepts, i.e. reality vs. representation (or real world ....

S. Gadia and C. Yeung. A Generalized Model for A Relational Temporal Database. In Proceedings International Conference on Management of Data, pages 251--259, Chicago, 1988.

....Mary [2,7) Tom [2,7) Tom [2,7) Mary [2,7) Mary [2,5) Tina [2,3) Mary [6,7) Tina [3,5) Tom [6,7) Tom Figure 3: The answer to the query in example 3 The answer to this query is shown in figure 3. As the reader can see, there is a loss of historical information during joins. In a subsequent paper [GY88] Gadia and Yeung extended the above model by removing the homogeneity assumption and allowing time stamps to be n dimensional i.e. subsets of T n where T is a given temporal domain. This extended model is able to represent valid time as well as transaction time (by taking 2 dimensional ....

.... and interpreting them accordingly) An interesting feature of the algebra presented for this model is its operators for temporal navigation (e.g. FirstInterval, FirstInstant and so on) Using these operators, queries like What was Tina s salary when she was rehired can be expressed [GY88] GV85] 5.3 The Historical Relational Data Model of Clifford and Croker Clifford and Croker presented the historical relational data model HRDM in [CC87] The interesting feature of this model is that it associates time stamps, called lifespans, not only with each attribute in a relation ....

[Article contains additional citation context not shown here]

Sashi K. Gadia and Chuen-Sing Yeung. A Generalized Model For a Relational Temporal Database. In Proceedings of ACM SIGMOD International Conference on Management of Data, pages 251--259, 1988.

.... temporal database has a narrow meaning in their work that it is a database made by consolidating the rollback database and the historical database. This term should not be confused with our general meaning of temporal database. Finally, another confusion arises in the work of Gadia and Yeung [13], in which the valid and transaction times of [26] were adopted for the demonstration of their n dimensional, symmetric time concept. However, the valid and transaction times of [13] were in fact not those of [26] but the event and transaction times of [7] respectively. To summarize, we identify ....

....with our general meaning of temporal database. Finally, another confusion arises in the work of Gadia and Yeung [13] in which the valid and transaction times of [26] were adopted for the demonstration of their n dimensional, symmetric time concept. However, the valid and transaction times of [13] were in fact not those of [26] but the event and transaction times of [7] respectively. To summarize, we identify several problems with the previous approaches. First, we think there has been a dichotomous classification of time concepts, i.e. reality vs. representation (or real world vs. ....

S. Gadia and C. Yeung. A Generalized Model for A Relational Temporal Database. In Proceedings International Conference on Management of Data, pages 251--259, Chicago, 1988.

....triplet of a valid time (e.g. interval) a transaction time (e.g. interval) and a value of the attribute domain. A tuple of n attributes is given by n sets of such triplets, each set representing the bi temporal information of an attribute of that tuple at dioeerent times. Gadia and Yeung s model [38], called the heterogeneous model, is a representative of this approach. Name Salary Paul, Jan90,Sep90] Feb90,uc] 30000, Jan90,Sep90] Feb90,uc] Paul, Mar91,Nov91] Dec90,Dec91] 30000, Mar91,Nov91] Dec90,Dec91] Paul, Mar91,Jul91] Dec91,uc] 30000, Mar91,May91] Dec91,uc] ....

....Clioeord and Croker s model. Each multi valued tuple has a lifespan. Even the rst tuple has a lifespan of two not adjacent time periodes. The functional aspects of this model is de ned such that at each chronon within a tuple s lifespan returns an attribute value of that tuple. Gadia and Yeung s [38] models is functional too in the same sense as Clioeord and Croker s model. Name Salary Lifespan Jan90 ## Paul Jan90 ## 30000 . Sep90 ## Paul Sep90 ## 30000 Mar91 ## Paul Mar91 ## 30000 . Aug91 ## Peter Aug91 ## 35000 . Jan90, Sep90 # Jan93 ## Peter Jan93 ## 40000 ....

S. K. Gadia and C. S. Yeung. A Generalized Model for a Relational Temporal Database. In Proceedings of the ACM SIGMOD International Conference on Management of Data, pages 251259, Chicago, IL, June 1988.

....Temporal Value Algebra or Model Dimensions Evolution Query Lang. CW83, CC88] Relational VT Step wise Algebra [KL83] ER TT User defined None [LDE 84] Relational TT Step wise None [SA85, SA86, Sno87, MS90] Relational VT TT Step Discrete Both [Tan86] Relational VT Step wise Algebra [Gad88, GV85, GY88] Relational Arbitrary Step wise Both [AQ86] ER TT Step wise Language [Ari86] Relational Arbitrary Step wise Both [SS87, SS88] Independent VT 4 types Algebra [MNA87] Relational VT Step wise Language [ABN87] Relational VT TT Step wise None [LJ88] Relational VT Step Discrete Algebra [Sar90a, ....

.... tod OO VT TT 4 types Language Timestamp Timestamp Schema ImplemLevel Kind Evolution entation [CW83, CC88] Attribute Points p : KL83] Attribute Points : p [LDE 84] Tuple Intervals p [SA85, SA86, Sno87, MS90] Tuple Points Intervals p p [Tan86] Attribute Intervals : Gad88, GV85, GY88] Attribute Set of Intervals : AQ86] Variable Points p [Ari86] Tuple Points : SS87, SS88] Tuple Points : MNA87] Tuple Intervals p : ABN87] Tuple Points : p [LJ88] Tuple Points Intervals : p [Sar90a, Sar90b] Tuple Intervals : p [KRS90] Tuple Points : GM91] Tuple Intervals ....

S. K. Gadia and C. Yeung. A generalized model for a relational temporal database. In Proc ACM SIGMOD, pages 251--259, 1988.

....valid time, under this assumption, this data model supports degenerate bitemporal relations as well as general transaction time relations. Gadia presents a multi dimensional data model which is in turn restricted to a two dimensional data model with valid and transaction time as the dimensions [31]. In this model, however, only data valid in the past may be stored. For example, it is impossible to store on May 11, 1995 the fact that Employee Kate will be in the Shipping department from September 1, 1995 until August 31, 1997. Therefore, the model does not support fully general bitemporal ....

S. K. Gadia and C.-S. Yeung. A Generalized Model for a Relational Temporal Database. In Proceedings of the ACM SIGMOD '88, pp. 251--259 (1988).

....this property only through the introduction of distinguished nulls when taking snapshots. We avoid this problem by proving a weaker property: we restrict reducibility to operations on valid time relations that have identical timestamps for all of their attributes, termed homogeneous relations [Gadia 1988]. Theorem 4 The valid time operators [ Gamma, Theta, oe and reduce to their snapshot counterparts when their arguments are homogeneous. The language in which the algebra is embedded also has some nice properties (proofs appear elsewhere [McKenzie Snodgrass 1990] Theorem 5 The ....

.... be made to the definitions to handle properly the temporal dimension [McKenzie Snodgrass 1991A] It is also possible to extend the algebra in a consistent fashion to support periodicity [Lorentzos Johnson 1988] multi dimensional valid timestamps [Bhargava Gadia 1989, Bhargava Gadia 1991, Gadia Yeung 1988] and non first normal form valid time relations with an arbitrary level of nesting [Roth et al. 1988, Schek Scholl 1986, Tansel Garnett 1989, Ozsoyoglu et al. 1987] For valid time indeterminacy, ordering plausibility is supported by an additional argument in temporal predicates and ....

Gadia, S.K. and C.S. Yeung. A Generalized Model for a Relational Temporal Database, in Proceedings of ACM SIGMOD International Conference on Management of Data. Association for Computing Machinery. Chicago, IL: June 1988, pp. 251--259.

....tuple oriented relational data model. TEER does not add new syntactical constructs to the EER model; instead, it gives new meaning to the existing EER modeling constructs making them temporal. 2.5. 1 The Representation of Time The time representation is similar to that proposed by Gadia and Yeung [14] for the relational model, but is adapted to the requirements of the ER model. A time interval, denoted by [t 1 ; t 2 ] is defined to be a set of consecutive equidistant time instants, where t 1 is the starting instant and t 2 the ending instant. The distance between two consecutive time instants ....

S. K. Gadia and C. S. Yeung. A Generalized Model for a Relational Temporal Database. In Proceedings of ACM SIGMOD International Conference on Management of Data, pages 251-- 259, Chicago, IL, June 1988.

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S. K. Gadia and C. S. Yeung. A Generalized Model for a Relational Temporal Database. In Proceedings of ACM SIGMOD, pages 251--259, Chicago, IL, June 1988.

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# S.K. Gadia and C.S. Yeung, "A Generalized Model for a Relational Temporal Database," Proc. ACM SIGMOD Int'l Conf. Management of Data, pp. 251--259, June 1988.

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S. K. Gadia and C. S. Yeung. A generalized model for a relational temporal database. In ACM SIGMOD, pages 251#259, 1988.

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S. K. Gadia and C. S. Yeung. A Generalized Model for a Relational Temporal Database. In Proceedings of ACM SIGMOD International Conference on Management of Data, pages 251--259, Chicago, IL, June 1988.

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