Developer's Guide - MapGuide Open Source - OSGeo
Developer's Guide - MapGuide Open Source - OSGeo
Developer's Guide - MapGuide Open Source - OSGeo
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
Overview of Features<br />
Understanding features is fundamental to being able to use the Map<strong>Guide</strong><br />
Web API. Nearly every application will need to interact with feature data in<br />
one form or another.<br />
Features are map objects representing items like roads (polylines), lakes<br />
(polygons), or locations (points).<br />
A feature source is a resource that contains a set of related features, stored in a<br />
file or database. Some common feature source types are SDF files, SHP files,<br />
or data in a spatial database.<br />
For example, you may have a feature source that contains data for roads.<br />
Feature sources can be stored in the library repository or in a session repository.<br />
A feature source identifier describes a complete path in the repository. For<br />
example,<br />
Library://Samples/Sheboygan/Data/RoadCenterLines.Feature<strong>Source</strong><br />
Within a single feature source there may be one or more feature classes. A<br />
feature class describes a subset of the features in the feature source. In many<br />
cases, there is one feature class for each feature source. For example, there may<br />
be a Roads feature class in the RoadCenterLines feature source.<br />
A feature class contains one or more features. Each feature has a geometry<br />
that defines the spatial representation of the feature. Features will also generally<br />
have one or more properties that provide additional information. For example,<br />
a feature class containing road data may have properties for the road name<br />
and the number of lanes. Feature properties can be of different types, like<br />
strings, integers, and floating point numbers. Possible types are defined in the<br />
class MgPropertyType.<br />
In some cases, a feature property will be another feature. For example, a Roads<br />
feature might have a Sidewalk feature as one of its properties.<br />
A map layer may contain the features from a feature class. The features are<br />
rendered using the feature geometry.<br />
The Web API Feature Service provides functions for querying and updating<br />
feature data.<br />
34 | Chapter 3 Working With Feature Data