Feature Collections seem to need important interfaces in order to support the needs of Catalogs and Catalog Services. These interfaces seem to be tightly coupled with Feature
Collection Metadata. Formal definition of feature identifier scope is required, and every scope implicitly has an association with the collection of features whose identifiers it can
resolve.
2.11. Summary of the Nine Layer Model
As a summary of the preceding sections, and as a reformulation of Figure 2-2, we present Figure 2-23.
name pith
select embed
measure fit
codify localize
survey locate
assemble
extent geo-value
Epistemic Interface
GIS Discipline
Interface
Local Metric
Interface
Community Interface
Spatial Reference Interface
Geometric Structure
Interface Feature
Structure Interface
Project Structure
Interface
member include
decompose
Real World; Essential
Language Conceptual
World; Natural
Language OGIS Points;
Coordinate Geometry
OGIS Geometry
World; OGIS WKTs
OGIS Feature World;
OGIS Features
Project World World View;
Information Community
Dimensional World;
Metric Language
Geospatial World;
GIS Language
Mathematical and Symbolic
Models of the World
Conceptual and Literal
Models of the World
encl ose
instance
attribu te
Attribute Schema
Interface
Geometry Schema
Interface
Project Schema
Interface
represent re
ali ze
skel eton
OGIS Feature Collection World
OGIS Feature Collection
Figure 2-23 Nine Layers of Abstraction with Additional Interfaces
The OpenGIS
®
Abstract Specification Page
23 Volume 5: Topic 5: Features
Using the notation of [1], we present Figure 2-23.
GIS World Real World
OGIS Feature World
OGIS Geometry World
OGIS Point World
Project World or World View
Dimensional World Conceptual World
name pith
model embed
measure fit
codify localize
survey locate
assemble
geo-value decompose
extent skeletonize
enclose
attribute instance
Attribute Schema
Spatial Reference System
Geometry Schema
OGIS Feature Collection World
realize
represent
Project Schema
include member
Attribute Reference System
Attribute
Figure 2-24 The Object Types of the Nine Layer Model
2.12. An Alternative Perspective to the Nine Layer Model
Figure 2-25 presents an alternative view of the various ways of defining multiple worlds, but from a language perspective. This view is equally valid but different. In particular,
the nine-layer model implies that the essence of all features is tied up in their spatial extents they are all drawn from a ‘Project World’ which is a ‘codification’ of the
‘Dimensional World’. However, we define features to be able to have many spatial extents - or none - and where the spatial extent of the feature may be of less importance
than its relationships to other features see Topic 8.
The OpenGIS
®
Abstract Specification Page
24 Volume 5: Topic 5: Features
Figure 2-25 Conceptual Model of the ‘Real World’ modelling process
2.13. Persistent Feature Identifiers
