Cyclic query processing issues in object-oriented databases are investigated. A data and cyclic query model is defined for an object-oriented database system, using a graph model. Then the efficient processing of a general object-oriented cyclic query is discussed. For efficient processing, a general cyclic query and the access plans generated for a given query are defined and a cost model is developed to determine the cost for each access plant generated. The retrieval algorithms used for actual data retrieval are also investigated.>

A class of external schemas derivable from a tree structured main schema is identified. It is shown that the properties of this class of schemas permit the construction of a processing interface such that predicates defined on an external schema can be evaluated in an occurrence structure disciplined by the main schema.

In the July 1972 issue of Datamation, Schubert (1972) discusses the database management capabilities of the April 1971 report of the CODASYL Data Base Task Group (DBTG) (1971). The April 1971 report has been accepted by the CODASYL Programming Language Committee for inclusion of the COBOL data manipulation language (DML) and its associated subschema into JOB COBOL. A new CODASYL committee has been established to develop the DBTG data description language (DDL) into a common data description language suitable for a complete designation of all the elements of a database which can then be assessed by extensions to existing programming languages and possibly a high-level self-contained language. It is the purpose of this paper to outline extensions to the proposed DML to supply a language capability (a) that is specifically designed to clarify and facilitate the writing of algorithms for processing hierarchical data structures, and (b) that provides facilities for manipulating structural data. We will show that the process of accessing the database on the bases of arbitrary Boolean functions of retrieval terms should not be left to the capabilities of the host language of the DML but should be made a part of the DML. In addition, the capability of the DML, as presently defined, to access a database on the basis of the values of data items is too restrictive and extensions to the present capabilities are proposed.

An approach to determining an appropriate file structure for a given application is presented, by outlining a methodology for comparing some important aspects of data management system performance. The aspect chosen for analysis is the processing time required to evaluate Boolean functions defined on data values contained within a file structure and select elements from the structure satisfying the expression.Two file structures are studied. The structures are each combinations of hierarchical and inverted file organizations, which differ in the use of the pointers contained in the inverted file. In one case they link a value to nodes corresponding to its occurrence in the data hierarchy and in the second they link a value to the entry which contains the node corresponding to an occurrence.Algorithms for processing within each of the structures are discussed. Each algorithm is then modeled, and approximating models developed for simulation of the algorithms.