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KML Extension for the MapSetJSON Specification

Authors
Trey Smith (Carnegie Mellon University)
Revision
Pre-0.1 draft
Date
31 Jan 2012
Canonical URL of this document
http://mapmixer.org/mapsetjson/ext/kml/0.1/
Further information
http://mapmixer.org/mapsetjson/

1   Introduction

This extension adds the ability to include KML map layers in a map set. It extends the MapSetJSON Core Specification.

This specification refers to the MapSetJSON Folder Extension and the MapSetJSON Include Extension.

2   Examples

To declare that a MapSetJSON document uses this extension:

"extensions": {
  "kml": "http://mapmixer.org/mapsetjson/ext/kml/0.1/"
}

An example KML node:

{
  "type": "kml.KML",
  "name": "Earthquake Intensity",
  "url": "http://mapmixer.org/mapsetjson/example/eqintensity.kml"
}

3   Definitions

The KML file format is defined by the KML OGC Standard. The KML Developer Reference is also useful.

4   KML Class

A KML object ("type": "kml.KML") declares a map layer that links to KML content.

The behavior of KML objects is modeled on the behavior of Include objects as specified in the MapSetJSON Include Extension. The KML subdocument is loaded in the same way as a MapSetJSON subdocument, and displayed similarly in the layer selection interface. When the KML object is visible, the appearance of the KML content in the map is defined by the KML OGC Standard.

We use the following rules to identify corresponding features of KML and MapSetJSON documents:

  • By default, the included node is the top-level tag of the KML subdocument. However, if the url member of the KML object contains a fragment identifier starting with a hash mark #, the fragment must match the id attribute of a tag in the KML document, and that tag is the included node.
  • For the purposes of controlling the layer selection interface, the following equivalencies hold between MapSetJSON members and KML members:
    • MapSetJSON open = KML <open>. Corresponding values: true = 1, false = 0.
    • MapSetJSON visibilityControl = KML <listItemStyle>.
  • Some viewer implementations may be able to display KML content without being able to introspect its internal structure in the layer selection interface. These implementations should document that they "implement the KML extension without introspection support".
Abstract class:
No
Inherits from:
Layer, folder.FolderLike

(No additional members defined.)

4.1   KML Example

{
  // members inherited from Object
  "type": "kml.KML",
  "id": "...",

  // members inherited from Node
  "name": "...",
  "crs": { (CRS object ) },
  "bbox": [
    [-180.0, -90.0],
    [180.0, 90.0]
  ],
  "description": "...",
  "subject": [
    "(Key word 1)",
    ...
  ],
  "coverage": "(Human readable description of temporal or spatial coverage)",
  "creator": "(Name of entity)",
  "contributors": [
    "(Name of entity 1)",
    ...
  ],
  "publisher": "(Name of entity)",
  "rights": "Copyright (C) ...",
  "license": "http://creativecommons.org/licenses/ ...",
  "morePermissions": "You may also ...",
  "dateCreated": "2012-01-30T12:00:00Z",
  "dateModified": "2012-01-30T12:00:00Z",
  "dateAdded": "2012-01-30T12:00:00Z",

  // members inherited from Layer
  "show": false,
  "drawOrder": 1000,
  "master": false,
  "url": "http://example.com/layer.kml#optionalIdOfTagInKMLDocument",

  // members inherited from folder.FolderLike
  "open": false,
  "visibilityControl": "check"
}
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