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We describe a network schema design algorithm that uses a well-designed relational schema as input. The resulting network database handles incomplete information, since we use only the modified foreign-key constraint and not the universal instance assumption. We believe that the repreaentative instance is a correct representation of information stored in the database. We show how to map the representative instance to the network database. We give two algorithms for translating a relational query to a network application program. The first algorithm is confined to relational queries that express selections and projections over the universal relation scheme. The second algorithm includes all relational queries over select, project and (natural) join. Optimization techniques are discussed for both types of trans'lation.

In this paper we address several problems relating to functional dependencies and network schemas. We investigate properties of the functional dependencies that are implicitly defined in a network schema. A definition for the satisfaction of functional dependencies by a network database is proposed, and then we give a sufficient condition for the global consistency of a network schema. A network schema is globally consistent if all its databases satisfy the functional dependencies that are implicitly defined in the schema. Finally, we describe a design methodology for producing a network schema whose set of implicitly defined functional dependencies implies a set of functional dependencies specified by the user.

New methods for retrieving records from a database with links are given so that records are retrieved only once and not multiple times as happens when using the traditional method of retrieval Improvements as great as 50 percent are expected for queries over databases containing only many-to-one relationships and much greater improvements are expected when many-to-many relationships are embedded in the database Furthermore, it is shown how to combine relational and network retrieval methods Relations, containing many tuples, are created during the evaluation of a network query Each relation is either joined with other relations or is used to continue the evaluation of the network query The methods given show how to optimize data retrieval from a relational database that is implemented using links, where each link represents a many-to-one relationship

In this paper we address several problems relating to functional dependencies and network schemas. We investigate properties of the functional dependencies that are implicitly defined in a network schema. A 'definition for the satisfaction of functional dependencies by a network database is proposed, and then we give a sulIicienB condition for the global consistency of a network schema. A network schema is globally consistent if 8ll its databases satisfy the functional dependencies that are implicitly defined in the schema. Finally, we describe a .design methodology for producing 8 network schema whose set of implicitly defined functional dependencies implies a set of functional dependencies specified by the user.