T. Imielinski, S. Naqvi, and K. Vadaparty, Querying design and planning databases, in "LNCS 566: Proceedings of 2nd International Conference on Deductive and ObjectOriented Databases, Munich, Germany, December 1991," 524--545.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....of approximations obtained in section 4. We discuss problems with using this approach, such as undecidability of certain preconditions that need to be checked to ensure well definedness of programs. As a solution to this problem, we suggest an encoding of approximation constructs with or sets [14, 15, 22, 31] and explain how the language for or sets from [22] is suitable for programming with approximations. In fact, a system based on this language [12] has been used in the problems of querying independent databases. 2 Preliminaries Partial objects and ordered sets Most models of partiality of data ....

....work on representing partiality via orders, the problem of choosing the right ordering was not considered. Recently, in [22, 21] a theory for deciding which order is suitable for which collection was developed. It turns out that v [ is suitable for sets 1 and v ] is suitable for or sets [14, 15]. Or sets, denoted by the angle brackets, are sets of exclusive possibilities, i.e. Name: Joe; Age:h25; 27i] says that Joe is 25 or 27 years old. Orderings suggest a natural approach to the semantics of partiality: an object may denote any other object that is above it. For example, Name: Joe; ....

T. Imielinski, S. Naqvi, and K. Vadaparty. Querying design and planning databases. In LNCS 566: Deductive and Object Oriented Databases, pages 524--545, Berlin, 1991. Springer-Verlag.

....27i, see figure 3. While structurally just a set, it denotes an integer, which is either 24 or 27. That is, there are two different views of or sets: structural, that concerns representation, and conceptual, that concerns meaning. This idea was present in the initial papers on or sets [INV91a, INV91b] and later was formalized and worked out in [LW96] 6 1.4 Toward a general theory There are a number of models for partial information in the database literature. Some of them are quite ad hoc, based on specific needs arising in particular applications. We have seen two sources of partiality: ....

T. Imielinski, S. Naqvi, and K. Vadaparty. Querying design and planning databases. In C. Delobel, M. Kifer, and Y. Masunaga, editors, LNCS 566: Deductive and Object Oriented Databases, pages 524--545, Berlin, 1991. Springer-Verlag.

....algorithms, both in space and time. 1 Introduction Information stored in databases is usually incomplete. One of the typical sources of partiality, along with null values [AKG91, IL84] is disjunctive information that occurs primarily in the areas of design and planning, as was noticed in [INV91a, INV91b]. It may also arise due to conflicts that occur when different databases are merged. A number of approaches to querying databases with disjunctions are known in the literature. The idea of using and or trees to develop a new object oriented data model with an ad hoc query facility was exploited ....

....It may also arise due to conflicts that occur when different databases are merged. A number of approaches to querying databases with disjunctions are known in the literature. The idea of using and or trees to develop a new object oriented data model with an ad hoc query facility was exploited in [INV91a, INV91b]. The query complexity in this model was analyzed in [IMV89] Recently, a functional query language for databases with disjunctions was designed [LW93a] and implemented [GL94] In these papers two kinds of queries have been distinguished: structural queries ask questions about the data stored in a ....

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T. Imielinski, S. Naqvi, and K. Vadaparty. Querying design and planning databases. In LNCS 566: DOOD-91, pages 524--545. Springer-Verlag.

....to that of Rounds is used to provide semantics for or sets. We also treat or sets in the context of partial information in databases. 1 Introduction Applications within design, planning, and scheduling areas have motivated Imielinski, Naqvi, and Vadaparty to introduce the notion of or set [17, 18]. Although or sets are in essence disjunctive information, they are distinguished from the latter by having two distinct interpretations. An or set can either be treated at a structural level or at a conceptual level. The structural level concerns the precise way in which an or set is constructed. ....

....to its normal form. A query at the conceptual level is then simply a query performed on normal forms. Related work. Imielinksi, Naqvi, and Vadaparty stressed the applications of or sets in design and planning areas and informally explained the distinction between structural and conceptual queries [17, 18]. The semantics and query language proposed by [17] are rather involved. They defined a concept of order independence which is related to the notion of normalization but is based on assigning object identifiers, and demonstrated a sufficient condition for order independence. In addition, they were ....

[Article contains additional citation context not shown here]

T. Imielinski, S. Naqvi, and K. Vadaparty. Querying design and planning databases. In LNCS 566: Deductive and Object Oriented Databases, pages 524--545, Berlin, 1991. Springer-Verlag.

....of values for each or type. An example of this kind of hypothetical query might be does an allocation of classes to teachers exist, in which no teacher takes more than three classes per week Such queries, expressed in a version of Datalog, can be evaluated using standard SLD resolution [17]. Other work [26] has used an adaptation of the Magic Sets approach to evaluate queries involving parametrised constraints. Although our own language does not currently allow hypothetical queries of this kind, it could easily be modified to do so, simply by removing the commit phase of the ....

T. Imielinski, S. Naqvi, and K. Vadaparty. Querying Design and Planning Databases. In Delobel et al. [4], pages 524--545.

....or sets. We also treat or sets in the context of partial information in databases. To appear in Journal of Computer and System Sciences 1 Introduction Applications within design, planning, and scheduling areas have motivated Imielinski, Naqvi, and Vadaparty to introduce the notion of or set [17, 18]. Although or sets are in essence disjunctive information, they are distinguished from the latter by having two distinct interpretations. An or set can either be treated at a structural level or at a conceptual level. The structural level concerns the precise way in which an or set is represented. ....

....to its normal form. A query at the conceptual level is then simply a query performed on normal forms. Related work. Imielinski, Naqvi, and Vadaparty stressed applications of or sets in design and planning areas and informally explained the distinction between structural and conceptual queries [17, 18]. The semantics and query language proposed by [17] are rather involved. They defined a concept of order independence which is related to the notion of normalization but is based on assigning object identifiers, and gave conditions for order independence. In addition, they were able to ....

[Article contains additional citation context not shown here]

T. Imielinski, S. Naqvi, and K. Vadaparty, Querying design and planning databases, in "LNCS 566: Proceedings of 2nd International Conference on Deductive and ObjectOriented Databases, Munich, Germany, December 1991," 524--545.

....amount of non determinism implied in these problems (e,g. the design is partially specified or the tasks are not already assigned) which is difficult to represent, whether in a commercial objectoriented database or in a relational database. Therefore, a natural extension to a data model [AKG87] [INV90] [Ca91a] is to introduce disjunctive (or incomplete) information, which yields to the notion of global constraints to restrict the possible completions of the incomplete information. For instance, the budget for a design will be seen as a global constraint on all the design choices (the total cost ....

....information, also seen as incomplete information [AKG87] Disjunctive information is used to represent choices that are not made yet in a design or a planning problem. In the LAURE model, we attach disjunctive information to mono valued attributes; another solution would be to introduce OR objects [INV90], but using relations simplifies the data model. Each mono valued relation may be given a set of possible values for a given object x, either directly such as in: size(John) 162, 177, 190 ; color(my ball) blue,green or for a set of given objects such as in the following declaration: x ....

[Article contains additional citation context not shown here]

T. Imielinski, S. Naqvi, K. Vadaparty. Querying Design and Planning Databases. Proc. of DOOD91, Munich, 1991.

....We have obtained upper bounds for the cost of normalization. An approach related to that of Rounds is used to provide semantics for or sets. 1 Introduction Applications within design, planning, and scheduling areas have motivated Imielinski, Naqvi, and Vadaparty to introduce the notion of or set [13, 14]. Although or sets are in essence disjunctive information, they are distinguished from the latter by having two distinct interpretations. An or set can either be treated at a structural level or at a conceptual level. The structural level concerns the precise way in which an or set is ....

....to its normal form. A query at the conceptual level is then simply a query performed on normal forms. Related work. Imielinksi, Naqvi, and Vadaparty stressed the applications of or sets in design and planning areas and informally explained the distinction between structural and conceptual queries [13, 14]. The semantics and query language proposed by [13] are rather involved. They defined a concept of order independence which is related to the notion of normalization but is based on assigning object identifiers, and demonstrated a sufficient condition for order independence. In addition, they ....

[Article contains additional citation context not shown here]

T. Imielinski, S. Naqvi, and K. Vadaparty. Querying design and planning databases. In LNCS 566: Deductive and Object Oriented Databases, pages 524--545, Berlin, 1991. Springer-Verlag.

....the addition of the conditional is a convenience; it does not greatly affect the expressive power of R( 4. 5 Discussion Nested relational algebras were introduced to relax the first normal form restriction originally imposed by Codd [15] and considered unacceptable in many modern applications [41, 40, 26, 29]. The earliest definition was that of Jaeschke and Schek [29] who allowed the components of tuples to be sets of atomic values. That is, nesting of relations was restricted to two levels. This restriction was relaxed by Thomas and Fischer [57] who allowed relations to be nested to arbitrary depth. ....

T. Imielinski, S. Naqvi, K. Vadaparty, Querying design and planning databases, in "LNCS 566: Proceedings of 2nd International Conference on Deductive and Object Oriented Databases," 524--545, Munich, Germany, December 1991.

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T. Imielinski, S. Naqvi, and K. Vadaparty, Querying design and planning databases, in "LNCS 566: Proceedings of 2nd International Conference on Deductive and ObjectOriented Databases, Munich, Germany, December 1991," 524--545.

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