M. Levene and G. Loizou. Semantics for Null Extended Nested Relations. ACM TODS, 18(3):414--459, 1993.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....require effective storage, efficient access and inference of large amounts of data with complex structures. However, such capabilities are not directly supported by the existing database systems. In the past decade, various advanced data models such as nested relational and complex object models [1, 3, 9, 14, 19, 28, 31, 32] and object oriented models [5, 11, 15, 17, 18] were developed to support the storage of large amounts of data with complex structures. On the other hand, a lot of interests arose in the deductive database approach which integrates the logic programming and relational database techniques and ....

M. Levene and G. Loizou. Semantics for Null Extended Nested Relations. ACM TODS, 18(3):414--459, 1993.

....it would not affect the reasoning component in a significant way. Also, an adaptation to data models other than the relational (deductive) one would be useful. Especially, an adaptation to an object oriented data model would be desirable. This could be based on existing work such as F logic [18], Chimera [10] or DEL [14] The present reasoning component is guaranteed to find all minimal models, but may also generate non minimal ones. In the case of Satchmo there is a variant that generates exactly the minimal models [9] The techniques used to achieve that should be combined with ....

....[16] J. Hintikka. Model minimization an alternative to circumscription. Journal of Automated Reasoning, 4:1 14, 1988. 17] M. Kettner and N. Eisinger. The tableau browser SNARKS (system description) In 14th Int. Conf. on Automated Deduction (CADE) pages 408 411. Springer LNAI 1249, 1997. [18] M. Kifer, G. Lausen, and J. Wu. Logical foundations of object oriented and frame based languages. Journal of the ACM, 1995. 19] S. Lorenz. A tableau prover for domain minimization. Journal of Automated Reasoning, 13:375 390, 1994. 20] R. Manthey. Satisfiability of integrity constraints: ....

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Mark Levene and George Loizou. Semantics for null extended nested relations. ACM TODS, 18(3):414--459, 1993.

....and sets in deductive databases. In particular, we present a deductive language RLOG II based on Relationlog. RLOG II supports partial and complete sets and also null unknown ( and inconsistent ( values. As a result, the null extended nested relational algebra operations as defined in [7] can be represented directly and more importantly recursively which makes it more powerful than other logic based languages. such as LPS [6] COL [1] LDL [4] and Relationlog [8] This work provides a firm logical foundation for nested relational and complex object databases that have both ....

Mark Levene and George Loizou. Semantics for Null Extended Nested Relations. ACM TODS, 18(3):414--459, 1993.

....of data with complex structures. In this paper, we describe query processing in the Relationlog system. In particular, we illustrate the extended semi naive and magic set techniques used in Relationlog. 1 Introduction During the past decades, the nested relational and complex object models [1, 5, 11, 12, 15, 18, 21, 22] were developed to extend the applicability of the traditional relational model to more complex, non business applications such as CAD, image processing and text retrieval [2] Another important direction of intense research has been in using a logic programming based language Datalog [8, 23] as ....

Mark Levene and George Loizou. Semantics for Null Extended Nested Relations. ACM TODS, 18(3):414-459, 1993.

....that the unique minimal and supported model, if it exists, can be computed bottom up, and therefore used as the intended semantics of the program. 1 Introduction In the past decade, there has been a lot of interest in nested relations, whose tuple components may be sets, tuples or even relations [2, 8, 11, 12, 14, 15]. The extended relational algebra and calculus have been given for such kind of databases and are proved equivalent [15] Another important direction of intense research has been in using logicbased languages, such as Datalog, as database query languages. Such languages provide a very natural way ....

Mark Levene and George Loizou. Semantics for null extended nested relations. ACM TODS, 18(3):414--459, 1993.

....nested relations, complex values, minimal model semantics, fixpoint semantics. A preliminary version appeared as an extended abstract in the Proceedings of the International Logic Programming Symposium, 1995. 1 Introduction In the past decade, the nested relational and complex value models [2, 14, 17, 21, 25, 26, 6] were developed to extend the applicability of the traditional relational model [13, 28] to more complex, non business applications such as CAD, image processing and text retrieval [3] Extended relational algebra and calculus are provided for such kind of models. It has been proved that extended ....

Mark Levene and George Loizou. Semantics for null extended nested relations. ACM TODS, 18(3):414--459, 1993.

....structures are also sometimes represented as directed acyclic graphs (figure 4b) a) F: G: 1 J : j1 K: H: h1 I : 1 null t 1 = b) F G H I h1 j1 null J K Figure 4. Reentrancy or coreference. 3. Model Some of the notation and terminology is based on [Maie83] Roth85] [Leve93]. 3.1. Recursive tuples We will assume that all attributes (or features) are contained in a finite set U = F 1 , F 2 , F p , called the universal set of attributes. A feature structure database scheme (or fs database scheme) is a set of feature structure schemes (or fsschemes) of the ....

....on, the termattributes will be used instead of features. 2 This should not be confused with nested relational models where attribute values can be sets of tuples (e.g. Abit86] Roth85] 3 Subsumption is inconsistently defined sometimes as carrying more information (e.g. Maie83] Roth85] [Leve93]) or as carrying less information (e.g. Shie86] Poll87] Here we will use the first definition. 4 Defining feature structure schemes amounts to considering typed feature structures, as in [Poll87] 5 Here acyclicity of the coreference relation results from the acyclicity of the fs schemes. ....

Levene, M. and Loizou, G. Semantics for null extended nested relations. ACM Transactions on Database Systems 18, 3 (1993), 141-159.

....with the work on partial and complete sets and complete tuples into a uniform framework and study how to define the semantics of a database which allow both partial and complete tuples and sets. The key feature is the introduction of the two notions: equivalence ( and equality ( as in [18] so that for the two special values (null unknown) and (inconsistent) introduced in [4] we have = but 6= 6= Second, we propose a deductive language for complex objects with null unknown ( and inconsistent ( values called RLOG II based on Relationlog [23, 25] ....

....for complex objects with null unknown ( and inconsistent ( values called RLOG II based on Relationlog [23, 25] Here II means that the proposed language is the successor of Relationlog with both and added. It supports the null extended nested relational algebra operations as defined in [18] directly and more importantly recursively which makes it more powerful than other logic based languages such as the Bancilhon Koshafian calculus [4] LPS [17] Hilog [9, 10] L 2 [16] COL [1] LDL [5] Relationlog [23, 25] A stratification in the spirit of several other researchers [1, 3, ....

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Mark Levene and George Loizou. Semantics for Null Extended Nested Relations. ACM TODS, 18(3):414--459, 1993.

....model theoretic semantics, which captures the intended semantics of nested sets, tuples and relations, and also a well defined proof theoretic semantics which coincides with its model theoretic semantics. 1. INTRODUCTION In the past decade, the nested relational and complex value models [2, 6, 14, 15, 18, 21, 25, 26] were developed to extend the applicability of the traditional relational model [13, 28] to more complex, non business applications such as CAD, A preliminary version appeared as an extended abstract in the Proceedings of the International Logic Programming Symposium, 1995. Address correspondence ....

Mark Levene and George Loizou. Semantics for null extended nested relations. ACM TODS, 18(3):414--459, 1993.

....instance approach [3, 13, 15, 24, 26] In the weak instance approach to the UR model, the representative instance (RI) 24, 26, 27] becomes the underlying data structure of the UR model, which is suitable for storing all the data in the database in a single relation. The nested relational model [1, 17, 28, 34] was developed in order to extend the applicability of the flat relational model to more complex non business applications. Nested relations do not necessarily conform to the first normal form assumption of the flat relational model [8] thus allowing hierarchically structured complex objects to ....

....nested relations by defining the nested universal relation model (nested UR model) In particular, we extend the weak instance approach to the UR model to the nested weak instance approach to the nested UR model. EXAMPLE 1.1. Schemas of nested relations are represented graphically by scheme trees [17], such as T shown in Fig. 1.1. The nested relation scheme (NRS) of T, denoted by R(T) is: 6 AIRLINE AIR CODE (FLIGHT NO (PASSENGER) CREW) AIRPORT PORT CODE) where the higher order attributes are marked with in order to distinguish them from the zero order attributes [1] ....

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M. LEVENE AND G. LOIZOU, Semantics for null extended nested relations, ACM Trans. Database Systems 18, No. 3 (1993), 414-459.

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