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DCW coverage-level record layout. |
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|  MIL-D-89009
are organized in subdirectories on the basis of physical
tile partitions. Spatial indexing occurs on the
primitive level and is implemented for each primitive
table. DCW coverage contents are described in 3.8.6,
and BROWSE coverage contents are described in 3.8.7.
The primitive-level record layout is described in 3.8.8.
b. Coverage topology. The topology level of each coverage
is defined by the types of feature classes present. A
coverage with level 0 topology contains a point feature
class only. Coverages with level 2 topology must
contain a line feature class and may also contain a
point feature class. Level 3 topology coverages must
contain an area feature class. The topology level of
each coverage is specified in the coverage description
table within each library (TABLES 8 and 12). The DCW
coverages represent level 0, 2, and 3 topology. The DCW
does not provide topology between coverages.
3.8.6
DCW coverage-level record layout. A DCW coverage is a
grouping of thematically consistent data. All data within the
thematic layer are represented by and contained within a single
coverage. Within the coverage there may be up to three geographic
feature classes: point, line, and area; and one cartographic
feature class: text. A VPF feature class is logically defined as
the combination of a feature table and a primitive table. DCW
contains 34 simple (area, line, and point) and 12 text feature
classes. DCW does not contain any complex feature classes. DCW
thematic layers, coverages, and feature classes are listed in
TABLE 14. Other coverages implemented in the DCW libraries are
listed in TABLE 15.
a.
Feature class schema tables. Each DCW library coverage
contains one feature class schema table. The feature
class schema table describes the relationship between
each feature table and associated primitive table within
the coverage according to the primary and foreign keys
of the tables (TABLES 16 to 35).
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