EXPRESS is an experimental prototype data translation system which can access a wide variety of data and restructure it for new uses. The system is driven by two very high level nonprocedural languages: DEFINE for data description and CONVERT for data restructuring. Program generation and cooperating process techniques are used to achieve efficient operation.This paper describes the design and implementation of EXPRESS. DEFINE and CONVERT are summarized and the implementation architecture presented.The DEFINE description is compiled into a customized PL/l program for accessing source data. The restructuring specified in CONVERT is compiled into a set of customized PL/l procedures to derive multiple target files from multiple input files. Job steps and job control statements are generated automatically. During execution, the generated procedures run under control of a process supervisor, which coordinates buffer management and handles file allocation, deallocation, and all input/output requests.The architecture of EXPRESS allows efficiency in execution by avoiding unnecessary secondary storage references while at the same time allowing the individual procedures to be independent of each other. Its modular structure permits the system to be extended or transferred to another environment easily.

the resulting set of assertions would have been the same but the subset of assertions added by a particular query might have been different. Figure 16 contains a data structure diagram for the design that was created by the system. The DOCTOR-PATIENT confiuency is detected from ABOVE assertions made in the second and third queries, and the base for the confluent hierarchy, the TREATMENT record, is discovered from assertions made in the first and second queries. The ABOVE assertions from queries five and six are erased because of redundancy. Only five ABOVE assertions remain, resulting in five of the sets (excluding SYM13 and SYM15) of Figure 16.The INORABOVE assertions are reduced to eleven, with one assertion for each item except for DOCNAME.

In this paper a ffle organization scheme designed to replace the use of the popular secondary index filing scheme (or inverted files on secondary key fields) is described. Through the use of redundancy and storing keys (or access numbers of the records) that satisfy difFerent combinations of secondary index values in "buckets," it is possible to retrieve all keys satisfying any input query derived from a subset of fields by a single access to an index file, although each bucket may be used for many combinations of values and a combination of buckets moy be required for a given query.The method which, in its degenerate case, becomes the conventional secondary index filing scheme works similarly but has the following advantages: (1) the elimination of multiple accesses in many cases; (2) the elimination of false drops;(3) the elimination of computer time to perform intersection of key sets each qualified for one secondary index field only; and (4) the avoidance of long strings of keys when an Index field appearing in a query has very few possible values. Redundancy, in some cases, is the same as the secondary indexing method. In the genera! case, trade-ofF between the number of accesses for query and redundancy exists.

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The results of a study of eight different key-to-address transformation methods applied to a set of existing files are presented. As each method is applied to a particular file, load factor and bucket size are varied over a wide range. In addition, appropriate variables pertinent only to a specific method take on different values. The performance of eaeh method is summarized in terms of the number of accesses required to get to a record and the number of overflow records created by a transformation. Peeularitiesof each method are discussed. Practical guidelines obtained from tbe results are stated. Finally, a proposal for further quantitative fundamental study is outlined.