S. Gadia. A Homogeneous Relational Model and Query Languages for Temporal Databases. ACM Transactions on Database Systems, 13(4), 1988.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....community, a relation in the temporal relational model is called heterogeneous when its attribute values have di#erent period of existence [ Tansel and Tin, 1998 ] Both temporary and unmarked relationships admit heterogeneous values. However, they can be forced to have homogeneous tuples [ Gadia, 1988 ] i.e. the values of a tuple are valid on the same time period by using global features to map the ER roles. McBrien et al. 1992 ] enforce temporal constraints on the validity time of instances of entities involved in heterogeneous relationships. The original ert model [ Theodoulidis ....

S.K. Gadia. A homogeneous relational model and query languages for temporal databases. ACM Transactions On Database Systems, 13:418--448, 1988.

....department from September 1, 1995 until February 29, 2000. Therefore, the model does not support fully general bitemporal relations, but supports instead retroactive bitemporal relations. The restriction to retroactive data is inherited from an earlier (retroactive) valid time data model [Gad88] Sarda proposes another specialized temporal data model in which current facts may be appended and where so called retrospective updates (changes to information about the past) are possible [Sar90] Hence, the transaction time is always equal to or after the valid time, and, like the previous ....

....is then represented by a sequence of consecutive chronons, where each chronon represents all instances that occurred during the chronon. We may also represent a sequence of chronons simply by the pair of the starting and terminating chronon. Unions of intervals are termed temporal elements [Gad88] The domain of valid times is given as D V T = fc k g, and the domain of transaction times may be given as D TT = fc j g. A valid time chronon c is thus a member of D V T , a transaction time chronon c is a member of D TT , and a bitemporal chronon c = c ) is an ordered ....

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S. K. Gadia. A Homogeneous Relational Model and Query Languages for Temporal Databases. ACM Transactions on Database Systems, 13(4):418--448, December 1988. 45

....a temporal relation into a single tuple with the same non timestamp attribute values and a timestamp that is the finite union of intervals that precisely contains the chronons in the timestamps of the value equivalent tuples. Finite unions of time intervals are termed temporal elements [Gad88] The definition of coalesce uses the function chronons that returns the set of chronons contained in the argument interval. YoX V V 2, u ( c d fe g h j An l, c rA T T o 2A T 2B A 2A rA T T o 2A q q ....

S. K. Gadia. A Homogeneous Relational Model and Query Languages for Temporal Databases. ACM TODS 13(4): 418-448, 1988.

....cope with the problem of supervising a temporal database for insertions and deletions in order to conserve its consistency and or completeness [18] but only with some of the issues concerning intelligent retrieval of temporal data. The following example is similar to an extended example found in [21]. Assume that the domain of interest consists of three tables, i.e. a salary table, a department table, and a manager table, as follows : 1. Salary Table Start End Name Salary Tref:salary(Name,Salary) 66 80 Mary 25 K 66,80 :salary(mary,25K) 26 80 Paul 23 K 26,80 :salary(paul,23K) 2. ....

Gadia S K (1988) A Homogeneous Relational Model and Query Languages for Temporal Databases. ACM Transactions on DataBase Systems, vol. 13, No 4, pp.418-448, December.

....to except that every state in whose timestamp has common points with has been recomputed so as to make that no longer the case in , and U (0 , The InsertState operation can therefore be seen to be a destructive, and hence non commutative, operation. For example, if 0 , [5 8],o2 and ( 1 6] o ) then ( 15 ] o) 5 8] 02) and if (7 , 5 8] o) and ( 1 6] o) then = 1 8] DeleteTimestamp takes a history H = V, 0, 7, X) and a timestamp of type 0 and yields a new history H = V, 0, 7, X ) The operation maps X into a state set X in ....

....common points with has been recomputed so as to make that no longer the case in , and U (0 , The InsertState operation can therefore be seen to be a destructive, and hence non commutative, operation. For example, if 0 , 5 8] o2 and ( 1 6] o ) then ( 15 ] o) [5 8],02) and if (7 , 5 8] o) and ( 1 6] o) then = 1 8] DeleteTimestamp takes a history H = V, 0, 7, X) and a timestamp of type 0 and yields a new history H = V, 0, 7, X ) The operation maps X into a state set X in which all states in X whose timestamp is such that ....

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S. K. Gadia. A Homogeneous Relational Model and Query Languages for Temporal Databases. ACM TODS, 13(4):418-448, 1988.

.... of databases with NOW and the querying of such databases has been covered extensively elsewhere [10] However, the impact on modifications of the presence of NOW in the database as well as in the modification statements themselves has not been covered, even though many temporal data models, e.g. [3, 6, 7, 8, 17, 20, 26, 32], assume that NOW can be stored in the database. Before defining the semantics of modifications on variable databases, we specify three requirements to the accommodation of NOW . Requirement R1 The conventional insert, delete, and update statements should be extended to permit constant ....

S. K. Gadia. A Homogeneous Relational Model and Query Languages or Temporal Databases. ACM TODS, 13(4):418--448, 1988.

....Given boolean = ftrue; falseg, ContainsTimestamp (H; true if 9 0 2 dom(states H ) 0 ) otherwise ContainsTimestamp (H; false. For example, if the state sets of two histories H 1 and H 2 both with V = int, TimeIntervals and identical , are 1 = fh[1 6] 12i; h[9 11]; 14ig and 2 = fh[5 10] 13i; h[13 20] 15ig then ContainsTimestamp before(H 1 ; 9 10] true and ContainsTimestamp after(H 2 ; 21 22] false. In contrast to ContainsTimestamp which queries a history for a true false reply, FilterBySnapshot exemplifies operations that query histories for ....

....H ) 0 ) otherwise ContainsTimestamp (H; false. For example, if the state sets of two histories H 1 and H 2 both with V = int, TimeIntervals and identical , are 1 = fh[1 6] 12i; h[9 11] 14ig and 2 = fh[5 10] 13i; h[13 20] 15ig then ContainsTimestamp before(H 1 ; [9 10]) true and ContainsTimestamp after(H 2 ; 21 22] false. In contrast to ContainsTimestamp which queries a history for a true false reply, FilterBySnapshot exemplifies operations that query histories for a reply that is itself a history. Given H = hV; i and H 0 = hV; 0 i, ....

[Article contains additional citation context not shown here]

S. K. Gadia. A Homogeneous Relational Model and Query Languages for Temporal Databases. ACM TODS, 13(4):418--448, 1988.

....adapted to the cross comparison of many temporal events and states. This approach surpasses many extensions to convex interval algebra that do not either apply on an indefinite number of intervals, or provide a clear semantics. Allens algebra cannot be applied as such to non convex intervals [11], it requires the identification of additional operations or a new form of algebra. For instance, 20] extends Allens algebra to non convex intervals by identifying six additional temporal operators which are based on the comparison of the boundaries of non convex intervals (minimum and maximum ....

Gadia, S., A homogeneous relational model and query language for temporal databases, ACM Transactions in Database Systems, 13, 418-448 (1988).

....is to better characterise the expressivity of temporal integrity constraints in order to axiomatise several extensions as proposed in the literature of temporal ER models. Currently, we are exploring the possibility to axiomatise the difference between homogeneous and heterogeneous relationships [5, 10], and to express historical marks (H marks) 11] This work was partially supported by the Foundations of Data Warehouse Quality (DWQ) European ESPRIT IV Long Term Research (LTR) Project 22469. ....

S. Gadia. A homogeneous relational model and query languages for temporal databases. ACM Transactions On Database Systems, 13:418--448, 1988.

....intersection, complement, difference) can be defined for them. However, the set of all intervals is not closed with respect to the above operations. For example, in , Q ) U.5YXM TSW) R Z INT . The notion of temporal element (union of a finite number of time intervals) [7] is therefore used. We will denote the set of all temporal elements over as ; is treated as a subset of , with the same set theoretic operations and ordering. 8:90; and [ are defined the same way as 8:90; and ; Figure 1 shows ....

S. Gadia. A Homogeneous Relational Model and Query Languages for Temporal Databases. ACM Transactions on Database Systems, 13(4), 1988.

....Therefore, temporal elements are finite unions of intervals. Note that, by this definition, an instant is also a temporal element. Thus, if the dimensional domain is the set of time instants T IME = 0; now] f0; 1; 2; nowg, then the dimensional elements are temporal elements [9]. For instance, 11; 40] 57; now] is a temporal element. In spatial databases users will like to use certain elementary spatial domains. Then dimensional spatial elements will be finite unions of those domains. Thus, if the dimensional domain is the spatial domain SPACE, then the dimensional ....

.... ) where a 1 ; an 2 AN are the names of the attributes of o, and v 1 ; vn 2 V are their values; c is the most specific class to which o belongs such that [ v 1 ] vn ] that is, all the object attributes have the same dimensional domain 2 (homogeneity assumption [9]) and v is in accordance with the attribute specification given in class c. The dimensional domain of an object o, denoted [ o ] is simply the domain of any of its attributes. 2 Note that, however, the attributes can assume different values in different dimensional elements of that domain, ....

S. K. Gadia. A Homogeneous Relational Model and Query Language for Temporal Databases. ACM Transactions on Database Systems, 13(4):418--448, 1988.

....operators between values at different granularities. Note that the finer than relationship establishes a partial order on a set of granularities G. Finally, we introduce the notion of temporal element with respect to a granularity. The notion of temporal element is formally introduced in [7]. A temporal element is a finite union of intervals. Intuitively, every subset of the set of granules associated with a granularity G is a temporal element. Thus, in what follows, given a granularity G, a temporal element TG with respect to such granularity is defined as TG = fG(i) j i 2 I; I ....

S. Gadia. A homogeneous relational model and query languages for temporal databases. ACM Transactions on Database Systems, 13(4):418--448, 1988.

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S. Gadia. A Homogeneous Relational Model and Query Languages for Temporal Databases. ACM Transactions on Database Systems, 13(4), 1988.

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S. K. Gadia. A Homogeneous Relational Model and Query Languages for Temporal Databases. ACM TODS, 13 (4):418-- 448, 1988.

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Gadia, S.K. "A Homogeneous Relational Model and Query Languages for Temporal Databases." ACM Transactions on Database Systems, 13, No. 4, Dec. 1988, pp. 418--448.

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S. K. Gadia. A Homogeneous Relational Model and Query Languages for Temporal Databases. ACM Transactions on Database Systems, 13(4):418--448, December 1988.

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S. K. Gadia. A Homogeneous Relational Model and Query Languages for Temporal Databases. ACM Transactions on Database Systems, 13(4):418--448, December 1988.

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S. K. Gadia. A Homogeneous Relational Model and Query Languages for Temporal Databases. ACM Transactions on Database Systems,1 3(4):41ff-- December1 988. 26

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S. K. Gadia. A Homogeneous Relational Model and Query Languages for Temporal Databases. ACM TODS,13 (4):418--448, 1988.

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S. K. Gadia. A Homogeneous Relational Model and Query Languages for Temporal Databases. ACM Transactions on Database Systems, 13(4):418--448, December 1988.

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S.K. Gadia, "A Homogeneous Relational Model and Query Languages for Temporal Databases," ACM Transactions on Database Systems 13(4), 418--448, 1988.

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S. Gadia. A homogeneous relational model and query languages for temporal databases. In ACM Transactions On Database Systems, 14, 418--448, 1988.

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S. Gadia. A Homogeneous Relational Model and Query Languages for Temporal Databases. ACM Transactions on Database Systems, 13(4):418--448, 1988.

No context found.

S. K. Gadia. A Homogeneous Relational Model and Query Languages for Temporal Databases. ACM TODS, 13(4):418--448, 1988.

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K. Gadia. An homogeneous relational model and query languages for temporal databases. ACM Transactions on Database Systems, 13(4):418-448 (1988).

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