 |
|||
|
Page Title:
Figure 1. DCW database implementation. |
|
||
| ||||||||||
|
|  MIL-D-89009
DCW DATABASE
DIRECTORY
4 DCW LIBRARY
1 BROWSE LIBRARY
DIRECTORIES
DIRECTORY
17 COVERAGE
8 COVERAGE
DIRECTORIES
DIRECTORIES
PER LIBRARY
MULTIPLE PRIMITIVE
NO TILES -
DIRECTORIES PER COVERAGE
PRIMITIVES STORED
BASED ON TILE SCHEME
IN COVERAGE DIRECTORY
FIGURE 1.
DCW database implementation.
3.7 DCW files. The DCW implements three types of VPF files:
directories, tables, and indices.
3.7.1
Directories. All DCW database files are contained in
a hierarchy of DOS directories. Contained within these
directories are the tables and indices that provide information
about the database.
3.7.2
VPF Tables. Each directory within the DCW database
contains a series of VPF tables. VPF tables consist of two parts:
(1) a header and (2) data records.
a. Header. The header defines the table contents,
including the column names, data types, field sizes, key
types, and descriptive information.
b. Data records. Following the header is a series of one
or more data records (or rows). Rows can be of fixed
length or variable length. VPF specifies which are
fixed and which are variable. Each row comprises a set
of fields containing information that corresponds to the
definitions of the columns. Each row is identified by a
sequential integer beginning with the number 1 that is
called a row identifier or ID. In fixed-length tables,
all rows in a table have the same number and type of
columns and field definitions. The values contained in
9
|
|
Privacy Statement - Press Release - Copyright Information. - Contact Us |
Click
here for thousands of PDF manuals