Showing papers on "Tuple published in 1982"

Logic for improving integrity checking in relational data bases

Abstract: When an "updating" operation occurs on the current state of a data base, one has to ensure the new state obeys the integrity constraints. So, some of them have to be evaluated on this new state. The evaluation of an integrity constraint can be time consuming, but one can improve such an evaluation by taking advantage from the fact that the integrity constraint is satisfied in the current state. Indeed, it is then possible to derive a simplified form of this integrity constraint which is sufficient to evaluate in the new state in order to determine whether the initial constraint is still satisfied in this new state. The purpose of this paper is to present a simplification method yielding such simplified forms for integrity constraints. These simplified forms depend on the nature of the updating operation which is the cause of the state change. The operations of inserting, deleting, updating a tuple in a relation as well as transactions of such operations are considered. The proposed method is based on syntactical criteria and is validated through first order logic. Examples are treated and some aspects of the method application are discussed.

An extended relational algebra with control over duplicate elimination

Abstract: In the pure relational model, duplicate tuples are automatically eliminated. Some real world languages such as DAPLEX, however, give users control over duplicate elimination. This paper extends the relational model to include multiset relations, i.e., relations with duplicate tuples. It considers three formalisms for expressing queries in this model: extended relational algebra, tableaux, and DAPLEX. It shows that, as in the original algebra, the equivalence problem for conjunctive expressions in the extended algebra can be solved using tableaux, and is NP-complete. Finally, it demonstrates that the extended algebra and DAPLEX have essentially the same expressiveness relative to conjunctive expressions.

Join operation processing system in relational model

Abstract: The present invention discloses a join operation processing system in a relational model where a data base processing mechanism provides at least maximum/minimum calculation execution means, reduction sort execution means and the join operation execution means. During the join operation for generating a new table linking tuples of a plurality of pertinent tables based on a common field or plurality of common fields, a minimum extraction range for determining the tuples to be processed is determined with respect to the join field or the plurality of join fields for each table which is considered as the object of the join. The operation rate is thereby improved by omitting the processing referring to unwanted data.

Toward logical data independence: a relational query language without relations

Abstract: One of the main goals of database systems, relational systems in particular, is to provide a degree of physical data independence for users and programs. Users should not need to know the exact physical storage structures to use the database, and should be protected from changes in those structures. We attempt to go a step further, to logical data independence. We want an interface to a relational database where a user need not be concerned with how the data has been partitioned into various relations. The natural relation schemes to be used, from a semantic point of view, may be decomposed in the database for normalization or redundancy reasons. Our approach essentially loads all the semantics onto the attributes. In our query language tuple variables are not bound to specific relations. Rather, the system uses the set of attributes, say X, that appear in a query with a tuple variable, say t, to combine the database relations to form a single relation with scheme X over which t ranges. We describe our method for constructing such a relation given the associated set of attributes X. When tuple variables are bound implicitly, the logical connectives 'and', 'or', and 'not' take on 'semantic overtones' since they can affect the binding. We discuss the motivation behind the chosen semantics for these connectives. Our goal is a powerful, yet concise, query language with natural semantics.

A domain based internal schema for relational database machines

Abstract: In this paper a method for relational database storage organization is presented.The method is based upon a disaggregation of the relations and a subsequent reaggregation to form the domains on which the relations are defined.A hierarchical organization of the domain is proposed in order to keep track of the relational entities (i.e. relations, tuples and attributes) that insist on the values present in the domains.Then we introduce an implementation technique, referred to as Data Pool, suitable to be processed by a database machine capable of "on the fly" track processing.Finally we present an analytic evaluation of the DP method and an example of database and query with performance comparison of the DP method with the most common flat file technique.The proposed method appears to be generally advantageous in storage occupancy; in data retrieval operations it is extremely effective when joins between permanent relations are performed. Good performances can be achieved with other relational operations using proper parallel architectures and, when temporary relations are involved, using special purpose devices.

The inference problem for template dependencies

Abstract: A template dependency is a formalized integrity constraint on a relational database, stating that whenever tuples exist in the database that agree on certain attributes, an additional tuple must also be present that agrees with the others in a specified way. It is shown that the inference problem for template dependencies is undecidable, that is, there can be no algorithm for determining whether a given dependency is a logical consequence of a given finite set of dependencies. The undecidability result holds whether or not databases are considered to be necessarily finite.

Removing restrictions in the relational data base model: an application of problem solving techniques

Abstract: The principal restrictions previously placed on the relational data base model have been removed in the L2 model, presented here. We extend the model to include null (i.e. unknown and non-relevant) values (even in keys), repetitions of tuples, functional dependencies, a very rich set of constraints and information originating from several sources. The programmed problem-solver ALICE is utilized to manipulate the constraints and to simplify relations: to answer a query, ALICE selects both the tuples which might answer the query upon appropriate substitutions for unknown values.

Spirit-III: an advanced relational database machine introducing a novel data-staging architecture with Tuple Stream Filters to preprocess relational algebra

Abstract: This paper proposes an advanced architecture of the relational database machine (RDBM), named SPIRIT-III, which is basically organized into a three-level memory hierarchy with a sophisticated data-staging and preprocessing architecture for executing relational algebra. SPIRIT-III aims at totally improving both I/O and CPU processing boundary problems and has two major architectural features. One is the introduction of the relational-database-oriented data-staging mechanism, called the look-ahead data-staging mechanism, which can optimally schedule data movement in the memory hierarchy. The other is to attach refined preprocessing mechanisms for relational algebra operations to data transfer lines connected between each memory stage. When a relation stages up or down in the memory hierarchy, these preprocessing mechanisms can function to select tuples and attributes needed by a query and to arrange the relation for parallel processing. SPIRIT-III provides three basic preprocessing filters, called as a whole the Tuple Stream Filter: the tuple selector, the attribute selector, and the grouping filter, implemented with a hash function, which rearranges an original relation and groups the relation into subrelations. The operation of this grouping filter is the primitive preprocessing operation for executing Join and Projection. Then, without the overhead of interprocessor communications, each microprocessor can execute relational algebra operations to a few subsegments assigned to it in parallel. Therefore, SPIRIT-III can perform Join and Projection operations by O (N/L) (L = number of microprocessors), whereas the early RDBMs required O (N X N/L). The proposed SPIRIT-III, which includes features from data-staging architecture to relational algebra execution architecture under the total concept, is the most powerful RDBM based on the state of the art.

Constituting methode for data base computer

Abstract: PURPOSE:To perform tuple readout and relational algebraic operation in parallel, by determining the transfer address of data through the value of data hashing with uniform distribution and making the data transfer and classification at the same time. CONSTITUTION:Through the operation instruction input 1 from a main controller 2, a logical device 5 reads a tuple (element of a set) from a storage medium 3 through a data readout/write-in device 4 to deliver it to a tuple transfer address determining device 6. The device 6 makes hashing by taking the value of attribute field being the object of the relational algebraic operation as a key to determine a relational algebraic operation logical device 8 of a tuple transfer address through the value and to transfer it to a data transfer device 7. The device 7 transfers the data transmitted in parallel consecutively from the device 6 to the device 8 designated with the device 6 for the relational algebraic operation, and the data readout/write-in 10 is made via an operation result output buffer 9 and the result of operation is outputted 12.

Relation algebra operating device

Abstract: PURPOSE:To achieve effective use of memories, by registrating new keys only to an associate memory device together with memory storage location information of a tuple main body and erasing unnecessary tuple from a memory and a buffer in a relational algebraic operator. CONSTITUTION:When a main controller 25 gives a tranfer request of a key and a tuple (element of a set) to a signal line 26, the key is outputted to a signal line 10 and the tuple main body is on a signal line 11 respectively and stored to a corresponding location of a tuple main body storage memory 15 and buffer 14 to be instructed 18, 19. In an associative memory logical device 12, if the key of the signal line 10 is registrated in an associative memory device 13 and a necessary/unnecessary signal is given to signal lines 22, 23. In case of registrated key, the transfer request of the next key is given to a device 25 and the result of retirieval and tuple storage location are given to a retrieval result storage buffer 16. In case of unregistrated key, the device 12 transfers an overflow signal of the memory 13 to the device 25 or the transfer request of the next key is outputted.

An tmplementation of impure suprogates

Abstract: Surrogates or internal identifiers can be made to facilitate both fast access and storage independence if they are implemented properly. Such an implementation is discussed here; it permits the tuplcs of a relation to be accessed very fast by primary key for both random and sequential search without retarding the performance of secondary keys. It employs a key compression and a hasiiing algorithm and attempts to place tuples on data pages in the primary key sequence. Subsequent updates are absorbed by a dynamic allocation of overflows. An indexing technique called a hash tree holds surrogates in primary key order, and facilitates fast sequential access. The access speed remains high even at a 90% load factor, without being significantly affected by storage reorganisation resulting from the addition of new attributes, deletion of old attributes or change of data page sizes. These techniques have been implemented in the PRECI database

Some formulas for generating Pythagorean n‐tuples

Abstract: The paper gives some explicit formulas for generating some solutions of the equation x 1 2 +x 2 2 + ... + x 2 n 1=x2 n in positive integers.