T.H. Merrett. Relational Information Systems. Reston Publishing Co., Reston, VA, 1984.  Home/Search   Document Not in Database   Summary   Related Articles   Check

.... with a speci c subset of the attributes Selection: selects tuples that satisfy a speci c condition Binary operations mu join: join operators that generalize set valued set operations sigma join: join operators that generalize logic valued set operations Operations on Domains Merrett[Mer84] proposed the domain algebra which consists of a set of operations that enable the arithmetic and related processing of the values of attributes in individual tuples. It allows the user to create new domains from existing ones. The generation of a new value from many values within a tuple or from ....

....developed at the Aldat lab of the School of Computer Science at McGill University. JRelix contains a database management systems (DBMS) which is responsible for organizing and storing data, and a programming language Aldat(Algebraic Data Language) based on relational algebra and domain algebra [Mer84, Yua98] JRelix incorporates complex constructs such as computations (functions and procedures) some object oriented paradigms, such as instantiation [Bak98, Zhe02] and nested relations [He97, Hao98] The event handler [Sun00] which is a characteristic of active database systems, and ....

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T. H. Merrett. Relational Information Systems. Reston Publishing Co., Reston, VA, 1984.

....for advanced requirements of data intensive applications. In addition to elementary access primitives (get, insert, delete, update and scan) for bulk structures, many DBPLs recognize the need to provide iteration abstractions like iterators [LG86] query expressions [BCD89] set operators [Mer84] or data deduction mechanisms in rule oriented systems [NT89, ERMS91] The rationale behind such declarative access specifications is to provide concise and optimizable notations for complex data selection and data construction tasks. For example, set comprehensions [Bun90, Wad90, ART91] nicely ....

T.H. Merrett. Relational Information Systems. Reston Publishing Co., Reston, Virginia, 1984.

....defined a set of relational operations and proved that they are relationally complete 1 [Cod72] Relations are considered atomic objects in the relational algebra, and access to tuples within a relation is precluded. Thus the notation and manipulations that must be done are greatly simplified [Mer84]. The operations are defined as following: ffl unary operations projection selection ffl binary operations joins: applied to relations that are union compatible oe joins: support set operations on relations 1 An algebra or calculus is relationally complete if, given any finite ....

....the rest of the thesis. Since all the design and implementation work in this thesis follows the conceptual framework of the existing Relix system, we will present only the subset of Relix related to this thesis. The theoretical foundation on which the development of Relix is based can be found in [Mer84], while the basic reference of Relix can be found in [Lal86] 2.1 Overview Relix is a RElational database programming Language in UNIX. It is an interpreted language written in C. It can accept and execute commands or statements from the command line. It can also accept Relix commands and ....

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T. H. Merrett. Relational Information Systems. Reston Publishing Company, Reston, Virginia, 1984.

.... at McGill University in 1986 [Lal86] The data manipulation language of Relix is Aldat, an algebraic data language proposed by Merrett [Mer77] The purpose of Relix is to provide an interactive environment of Aldat for exploring the concept of the relational database model as described in [Mer84] Relix is implemented in C. It consists of three main modules: a lexical analyzer, a parser, and an interpreter. The lexical analyzer is generated by Lex [Les75] to scan the user input into tokens. The parser is generated by Yacc [Joh75] to perform syntax analysis. The intermediate code ....

....to declare relations and attributes, and to create relations using relational expressions. Commands used to show the relations and attributes, to print the content of relations, to delete relations and attributes, etc, are also provided for the user to interact with the interpreter. Reference [Mer84] contains the detailed description of the relational and domain algebra in Relix. Recently, the domain algebra for relations with one level of nesting has also been implemented [He97] 2.2 The Nested Relational Model The nested relational model [Mak77, SS87, AFS89] was developed in order to ....

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T.H. Merrett. Relational Information Systems. Reston Publishing Co., Reston, VA, 1984.

.... University in 1986 [Lal86] The data manipulation language of Relix is Aldat, an algebraic data language proposed by Merrett [Mer77] The purpose of developing Relix is to provide users with an interactive version of Aldat for exploring the concept of the relational database model as described in [Mer84] Aldat has been extended to connect several programming language concepts to relations. ffl Scalars, arrays, and records[ML89] Together with associated operations and syntax, these data types are implemented as special cases of relations. For example, an one dimensional array can be ....

....4 discusses the implementation details of procedures in Relix. ffl Chapter 5 concludes the thesis with a summary and proposals for future work. Chapter 2 Relix Tutorial Relix, standing for Relational database on Unix, is a database programming language based on relational and domain algebra [Mer84] All the design and implementation work in this thesis follows the conceptual framework of existing Relix. The purpose of this chapter is to provide readers with enough Relix background to understand the rest of the thesis. Therefore, we will present only the subset of Relix that is relevant to ....

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T. H. Merrett. Relational Information Systems. Reston Publishing Company, Reston, Virginia, 1984.

....the desired path. Examples of such problems include the problem of finding the cheapest flight between two cities, the problem of finding the critical path in a project network, the problem of finding the most reliable path in a communication network, etc. Other examples of such problems appear in [1, 5, 8, 10 12, 24, 27, 29]. It has been observed [23] that a significant part of a wide variety of expert systems is the component that performs search over a sizable data space. For large data sets, a database management system is a practical necessity, and, therefore, it is prudent that the search portion of an expert ....

....in which the bounding procedure was incorporated, it was primarily done to keep the discussion concrete, and our techniques can easily be adapted to solve any number of useful and practical problems such as the shortest path, critical path, largest capacity path, path of maximum reliability, etc. [1, 5, 8, 10 12, 24, 27, 29]. Simulation results confirm that, using these techniques, a search can be expedited significantly without incurring a large storage penalty. A side benefit of this work is that we have shown how search can be organized to obtain successive approximations to the desired solution with considerable ....

T. H. Merrett, Relational Information System, Reston Publishing, Reston, Virginia, 1984.

....this family of algorithms can be generalized to solve path problems and to solve problems in which some selection criteria have been specified for source or destination nodes. 1. INTRODUCTION Transitive closure is regarded to be an important operation for the next generation of database systems [1, 5, 6, 12, 13, 15, 17, 19, 21], and considerable research has been devoted to designing algorithms for computing the transitive closure of database relations [2, 4, 9 11, 16, 24] These algorithms can be classified into three major families. Iterative algorithms, such as semi naive [4] logarithmic [10, 24] and variations ....

T. H. Merrett, Relational Information System, Reston Publishing, Reston, Virginia, 1984.

....as it generally requires the introduction of null values. However we shall make some use of this operator later. If we are prepared to introduce null values, then t [ is what [35] calls the null union , and S 1 t [ S 1 t ] S 2 ) t [ S 2 is what is sometimes called the outer join. Merret [26] describes this operation and also the left wing and right wing operations, which are S 1 t [ S 1 t ] S 2 ) and (S 1 t ] S 2 )t [ S 2 respectively. In some cases these operations preserve independence: Lemma 3 If S 1 and S 2 are independent, so are S 1 t ] S 2 , S 1 t [ S 1 t ....

T.H. Merrett. Relational Information Systems. Reston Publishing Co, PrenticeHall, Reston, Virginia, USA, 1984.

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T.H. Merrett. Relational Information Systems. Reston Publishing Co., Reston, VA, 1984.

....of approximate match techniques. The work is all directed to searches in relatively small texts, i.e. those not too large to fit into RAM. For texts that require secondary storage, O(n) is far too slow, and we need O(log n) or faster methods, as with conventional files containing separate records [17]. The price we must pay is to store an index, which must be built once for the whole text (unless the text changes) If we are interested in the text as an ordered sequence of characters, we must store 105 the text as well, and the index represents an additional storage requirement. If we are ....

T.H. Merrett. Relational Information Systems. Reston Publishing Co., Reston, VA, 1983.

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T. H. Merrett, Relational Information Systems, Reston Publishing Co., Reston, 1984.

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