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General Purpose Parameter Passing Scheme for Graphical Data Structure

IP.com Disclosure Number: IPCOM000045520D
Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 4 page(s) / 36K

Publishing Venue

IBM

Related People

Koenig, W: AUTHOR [+3]

Abstract

The invention relates to the accessing and modification of the relational data base tables as a parameter-passing medium among picture data structures. This avoids parameter-passing only by way of the coding hierarchy found in picture decomposition/composition routines. Clauses are used by an interpreter to select subsets of existing tables. Tables may be modified by the addition or change of columns.

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General Purpose Parameter Passing Scheme for Graphical Data Structure

The invention relates to the accessing and modification of the relational data base tables as a parameter-passing medium among picture data structures. This avoids parameter-passing only by way of the coding hierarchy found in picture decomposition/composition routines. Clauses are used by an interpreter to select subsets of existing tables. Tables may be modified by the addition or change of columns.

The basic idea is to decouple the parameter-passing graph from the picture decomposition graph. A table is triggered to "collect" parameter values from various tables rather than "being fed" parameters by a single table.

We stay with the relational representation (and, of course, assume that the appropriate access paths exist for performance). We also assume that the records have a unique identifier within the tables. Let us extend the previous example to two rectangles. For the sake of explanation we assume that the table RECTANGLE, which has the rectangle identifier (RID), contains the picture identifier (PID) of PICTURE. The tables are shown in Fig. 1 below.

PICTURE RECTANGLE PID SCALE X SCALE Y ... PID RID SCALE X SCALE Y ... 1 4 4 1 1 1 1 1 2 1 1

Fig. 1.

The full parameter-passing sequence is specified in a statement that is composed of a sequence of named clauses. Each clause refers to a table. The first clause defines the root of a hierarchy. The second clause refers to a table and identifies a set of records in this table that become the children of the root. A third clause defines the children of the records specified in the first clause or in the second clause, etc. In the Fig. 1 example, one can write: A: SELECT PICTURE
B: SELECT RECTANGLE MERE PID = A.PID.

This kind of specification is similar to the specification of joins in relational languages.

Note that records at a certain level can have more than one set of children, as will be illustrated later.

The parameter passing is handled in the following way: In each clause one can compute new fields for the record(s) in the specified set or for the parent record(s) on the parent/child path from the root to the clause being considered. The values of these fields are defined by an expression that can refer to any field value in the records already specified by any clause. One may also recompute a column of the permanent data structure and add, a WHERE clause to the computation so that only a subset of the selected records is recomputed. Additional, one can also specify input parameters.

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One would use, for example:

A: SELECT PICTURE WHERE PID = 1

A,B: SELECT RECTANGLE WHERE PID = A.PID AND RID = 1 COMPUTE LENGTH = A.SCALE X * SCALE X, WIDTH = A.SCALE Y *

SCALE Y

A,C: SELECT RECTANGLE WHERE PID = A.PID AND RID = 2 COMPUTE LENGTH = A. SCALE X * SCALp X n 2, WIDTH = A. SCALP Y * SCALE Y * 2.

The values available at the leaves of the hierarchy (LENGTH, WIDTH) can then be used for displaying the pic...