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Geometry-based Features


Contents

Related pages


Introduction

Geometry-centric data-models ("points, lines and polygons") have been common particularly in traditional GIS software, and to a lesser extent also in mining software systems. In contrast, GML and XMML are based on a feature-centric model (see GmlFeature), where the conceptual significance of the object is primary and geometry is "just another property".

Nevertheless it is the case that a system that intends to provide a lingua franca for exploration data must support the encoding of geometry-centric features from legacy systems. A set of feature types for this purpose is described here.

Each of the feature types in this module has a single geometry property with a value of gml:Point, gml:Curve, gml:Surface, or gml:Solid. The latter three of these are heads of substitution groups: in practice one of many concrete representations of the geometry of "lines", "polygons" and solids would be used (see GeometryComponents).

When generating XMML from a legacy system:
  • the preferable approach is for the operator to interpret the meaning of the objects that they want to export, and if possible assign them to an appropriate strongly-typed feature-type from XMML.
  • the next option is to use one of the "soft-typed" geometry-based feature types described on this page, and to note the type as the value of the featureType property. This retains the type information with the feature instance, which is broadly consistent with the principles of the general feature model (see GmlFeature).
  • the least preferable option is to use a soft-typed feature type, but omit the featureType property altogther.
Of course in the latter case it will be necessary for the party receiving the data to receive the feature type information in some other way. In the worst case this may be by visual interpretation in association with other features, in some kind of map or section view.

Schema documents

A set of geometry-based features are defined in four schema documents:

Example Instances

Model and Document Structure

Position Feature and derivatives

Model

pFeature.png pFeatureColour.png pFeatureProps.png

Explanation

The content model of xmml:PositionFeature extends xmml:PositionedFeatureType (see XmmlFeature) with
  • a property featureType, whose value is a token.
This should be used to record a name for the feature type, as a "soft-typing" approach to feature description.

xmml:ColouredPosition adds a defaultColour.

xmml:PositionWithProperties adds an unlimited set of soft-typed properties, using the notation from XmmlSchemaRepository:trunk/XMML/base.xsd, plus an unlimited set of relatedObservation properties.

Curve Feature and derivatives

Model

cFeature.png cFeatureColour.png cFeatureProps.png

Explanation

The content model of xmml:CurveFeature is derived in two steps:
  • xmml:CurvedFeatureType adds to xmml:BoundedFeatureType (see XmmlFeature)
    • a (optional) nodes property which may be used to contain a set of gml:Point elements to be used in the description of a complex geometry, and
    • a shape property, whose value is a gml:Curve
  • xmml:CurveFeatureType adds
    • the featureType property, whose value is a token.
This should be used to record a name for the feature type, as a "soft-typing" approach to feature description.

xmml:ColouredCurve adds a defaultColour.

xmml:CurveWithProperties adds an unlimited set of soft-typed properties, using the notation from XmmlCVS:XMML/base.xsd, plus an unlimited set of relatedObservation properties.

Surface Feature and derivatives

Model

uFeature.png

Explanation

The content model of xmml:SurfaceFeature is derived in two steps:
  • xmml:SurfacedFeatureType adds to xmml:BoundedFeatureType (see XmmlFeature)
    • a (optional) nodes property which may be used to contain a set of gml:Point elements to be used in the description of a complex geometry, and
    • a shape property, whose value is a gml:Surface
  • xmml:SurfaceFeatureType adds
    • the featureType property, whose value is a token.
This should be used to record a name for the feature type, as a "soft-typing" approach to feature description.

xmml:ColouredSurface adds a defaultColour.

xmml:SurfaceWithProperties adds an unlimited set of soft-typed properties, using the notation from XmmlCVS:XMML/base.xsd, plus an unlimited set of relatedObservation properties.

Solid Feature and derivatives

Model

oFeature.png

Explanation

The content model of xmml:SolidFeature is derived in two steps:
  • xmml:SolidedFeatureType adds to xmml:BoundedFeatureType (see XmmlFeature)
    • a (optional) nodes property which may be used to contain a set of gml:Point elements to be used in the description of a complex geometry, and
    • a shape property, whose value is a gml:Solid
  • xmml:SolideFeatureType adds
    • the featureType property, whose value is a token.
This should be used to record a name for the feature type, as a "soft-typing" approach to feature description.

xmml:ColouredSolid adds a defaultColour.

xmml:SolidWithProperties adds an unlimited set of soft-typed properties, using the notation from XmmlCVS:XMML/base.xsd, plus an unlimited set of relatedObservation properties.


Issues and change requests

Readers are invited to add issues to this table - select [Edit Table] below. It is not mandatory to enter a solution, but change requests are more likely to be implemented if a concrete solution is proposed.

%EDITTABLE{ header="| # | By | Timestamp | Component(s) | Description of issue | Proposed solution | Resolution |" format="| row, -1 | text, 25, Unknown | label, 0, 23 Sep 2017 13:41 | textarea, 3x25, Component(s) | textarea, 3x25, Description | textarea, 3x25, Proposal | select, 1, Unaddressed, Progressing, Resolved |" changerows="on" }%
# By Timestamp Component(s) Description of issue Proposed solution Resolution
1 My org 14 May 2004 collar location A big whinge a proposed solution Unaddressed
Topic revision: r12 - 15 Oct 2010, UnknownUser
 

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