Browse Prior Art Database

Relational Access Method Supporting Nested Data View

IP.com Disclosure Number: IPCOM000044116D
Original Publication Date: 1984-Nov-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 3 page(s) / 31K

Publishing Venue

IBM

Related People

Plouffe, WE: AUTHOR

Abstract

This invention relates to a method for efficient access and management of a hierarchically nested view of data in a relational data base system. A single record retrieval contains enough information to determine if the record satisfies the hierarchically nested view. The method steps include (a) storing data in single relations in which each record includes an environment field and other representations field, and (b) accessing data relationally such that each retrieved record satisfies the additional criteria of (1) its environmental field which must be contained in an environmental list, and (2) the other representations field which is not contained in the environmental list, whereby the data being retrieved constitutes the first representation on the path from the query node to the root of a representational tree.

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Relational Access Method Supporting Nested Data View

This invention relates to a method for efficient access and management of a hierarchically nested view of data in a relational data base system. A single record retrieval contains enough information to determine if the record satisfies the hierarchically nested view. The method steps include (a) storing data in single relations in which each record includes an environment field and other representations field, and (b) accessing data relationally such that each retrieved record satisfies the additional criteria of (1) its environmental field which must be contained in an environmental list, and (2) the other representations field which is not contained in the environmental list, whereby the data being retrieved constitutes the first representation on the path from the query node to the root of a representational tree. Data base systems currently support a single environment view of a shared data base to multiple users. This environment is defined by the data present in the data base, and the authorization mechanisms provided by the system. Such mechanisms are not capable of supporting nested environments, as defined below, without additional user programming and its resulting performance inefficiencies. Consider a tree structure of environments, where the root of the tree is the "common" environment. The environment of any node in the tree is defined recursively as follows: - The data environment of the root node consists only of that data directly entered into the "common" environment. - The data environment of a non-root node, N1, consists of the data entered directly into N1's environment and a subset of the environment defined for N1's parent node. This subset is the set of data items that exist in the parent's environment, and do not have a direct existence in N1's environment. The result is that when N1 retrieves a data item, the item is retrieved directly from N1's environment. If the data item is not found, then the environment of N1's parent is searched for the data item. If the data item is still not found, then the grandparent's environment is searched, etc., until either the data item is found or the data item is not found in the "common" environment. Such an environment definition is useful for supporting tree-structured directories, but their original motivation was to support the public, semi-public, and private data bases, as described in [*]. Unfortunately, as described above, the retrieval of a simple data item may involve several data base accesses to several environments. This invention presents an alternative which is efficient. The requirements for the efficient procedure are as follows: - A data item may have several representations (i.e., records), each in a separate environment. - Each data record contains two additional values - the identification of the environment into which it was entered, and a list of environment identifications into which other rep...