Declaration and addressing of Varying Density Arrays and structures

ABSTRACT

In current higher level languages arrays are parallelepiped in N dimensions, each dimension having an index range from a lower limit to an upper limit (both must be integers), the increment between valid index values being one. By removing the restriction of limits and increments to be integers or unity, a homogenously addressed sections or regions of an array is defined. Combining several of these regions each with its own limits and increments, but with common addressing, forms an array with varying data density. These new arrays are referred to as Varying Density Arrays (VDA). All data elements of a given region are restricted to a single format and structure. The element structure and format of one region in no way restricts elements in other regions. This generalization permits uniform addressing of conventional arrays, VDAs and PL/I or COBOL structures. This paper discusses (1) the concept of a VDA, (2) extensions to PL/I declarations to allow the definition of VDAs, (3) gives examples in PL/I and APL and discusses operations of VDAs and their subarrays. The paper touches on, but does not discuss, mappings to physical storage.

REFERENCES

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INDEX TERMS

Primary Classification:
  H. Information Systems
  H.2 DATABASE MANAGEMENT
      H.2.1 Logical Design
          Subjects: Data models

Additional Classification:
  H. Information Systems
  H.2 DATABASE MANAGEMENT
      H.2.3 Languages

General Terms:
Design, Languages, Management

Keywords:
APL, Addressing, Arrays, DBTG, Data base, Data structures, Declaration, PL/I, Schema