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<!DOCTYPE html>
<html lang="en">
<head>
<title>TileStache API</title>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<style type="text/css" title="text/css">
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</style>
</head>
<body>
<h1>TileStache API</h1>
<div id="intro">
<p>
TileStache is a Python-based server application that can serve up map tiles
based on rendered geographic data. You might be familiar with
<a href="http://tilecache.org">TileCache</a> the venerable open source WMS
server from MetaCarta. TileStache is similar, but we hope simpler and
better-suited to the needs of designers and cartographers.
</p>
<p>
<strong>This document covers TileStache version N.N.N</strong>.
</p>
<p>
See also <a href="http://tilestache.org/doc/TileStache.html">detailed module and class reference</a>.
</p>
</div>
<ul id="index">
<li>
<a href="#requesting-tiles">Requesting Tiles</a>
<ul>
<li><a href="#over-http">Over HTTP</a></li>
<li>
<a href="#in-code">In Code</a>
<!--
<ul>
<li><a href="#tilestache-gettile"><code>TileStache.getTile</code></a></li>
<li><a href="#tilestache-requesthandler"><code>TileStache.requestHandler</code></a></li>
</ul>
-->
</li>
</ul>
</li>
<li>
<a href="#serving-tiles">Serving Tiles</a>
<ul>
<li><a href="#wsgi">WSGI</a></li>
<li><a href="#cgi">CGI</a></li>
<li><a href="#mod-python">mod_python</a></li>
</ul>
</li>
<li>
<a href="#configuring-tilestache">Configuring TileStache</a>
<ul>
<li>
<a href="#caches">Caches</a>
<!--
<ul>
<li><a href="#test-cache">Test</a></li>
<li><a href="#disk-cache">Disk</a></li>
<li><a href="#multi-cache">Multi</a></li>
<li><a href="#memcache-cache">Memcache</a></li>
<li><a href="#s3-cache">S3</a></li>
</ul>
-->
</li>
<li><a href="#layers">Layers</a></li>
<li>
<a href="#providers">Providers</a>
<!--
<ul>
<li><a href="#mapnik-provider">Mapnik</a></li>
<li><a href="#proxy-provider">Proxy</a></li>
<li><a href="#url-template-provider">URL Template</a></li>
<li><a href="#mbtiles-provider">MBTiles</a></li>
</ul>
-->
</li>
<li><a href="#projections">Projections</a></li>
<li><a href="#metatiles">Metatiles</a></li>
<li><a href="#preview">Preview</a></li>
</ul>
</li>
<li>
<a href="#extending-tilestache">Extending TileStache</a>
<ul>
<li>
<a href="#custom-providers">Providers</a>
<!--
<ul>
<li><a href="#provider-rendertile"><code>provider.renderTile</code></a></li>
<li><a href="#provider-renderarea"><code>provider.renderArea</code></a></li>
<li><a href="#provider-gettypebyextension"><code>provider.getTypeByExtension</code></a></li>
</ul>
-->
</li>
<li><a href="#custom-caches">Caches</a></li>
<li><a href="#custom-configuration">Configuration</a></li>
</ul>
</li>
</ul>
<h2><a id="requesting-tiles" name="requesting-tiles">Requesting Tiles</a></h2>
<h3><a id="over-http" name="over-http">Over HTTP</a></h3>
<p>
TileStache URLs are based on a simplified TMS scheme:
</p>
<pre>
/{layer name}/{zoom}/{column}/{row}.{extension}
</pre>
<p>
An example tile URL might look like this:
</p>
<pre>
http://example.org/path/tile.cgi/streets/12/656/1582.png
</pre>
<p>
Interactive, slippy-map previews of tiles are also available:
</p>
<pre>
/{layer name}/preview.html
</pre>
<h3><a id="in-code" name="in-code">In Code</a></h3>
<h4><a id="tilestache-gettile" name="tilestache-gettile"><code>TileStache.getTile</code></a></h4>
<p>
Get a type string and tile binary for a given request layer tile.
</p>
<p>
Arguments to <code>getTile</code>:
</p>
<dl>
<dt>layer</dt>
<dd>
Instance of <code>Core.Layer</code> to render.
</dd>
<dt>coord</dt>
<dd>
One <code>ModestMaps.Core.Coordinate</code> corresponding to a single tile.
</dd>
<dt>extension</dt>
<dd>
Filename extension to choose response type, e.g. <samp>"png"</samp> or
<samp>"jpg"</samp>.
</dd>
<dt>ignore_cached</dt>
<dd>
Optional boolean: always re-render the tile, whether it's in the cache or
not. Default <samp>False</samp>.
</dd>
</dl>
<p>
Return value of <code>getTile</code> is a tuple containing a mime-type string
such as <samp>"image/png"</samp> and a complete byte string representing the
rendered tile.
</p>
<p>
See
<a href="http://tilestache.org/doc/TileStache.html#-getTile">TileStache.getTile</a>
documentation for more information.
</p>
<h4><a id="tilestache-requesthandler" name="tilestache-requesthandler"><code>TileStache.requestHandler</code></a></h4>
<p>
Generate a mime-type and response body for a given request. This is the function
to use when creating new HTTP interfaces to TileStache.
</p>
<p>
Arguments to <code>requestHandler</code>:
</p>
<dl>
<dt>config</dt>
<dd>
Required file path string for a JSON configuration file or a configuration
object with <var>cache</var>, <var>layers</var>, and <var>dirpath</var>
properties, such as
<a href="http://tilestache.org/doc/TileStache.Config.html#Configuration"><code>TileStache.Config.Configuration</code></a>.
</dd>
<dt>path_info</dt>
<dd>
Required end portion of a request URL including the layer name and tile
coordinate, e.g. <samp>"/roads/12/656/1582.png"</samp>.
</dd>
<dt>query_string</dt>
<dd>
Optional, currently-unused placeholder for possible future query string
use. Or maybe an explicit deterrent from ever building such a thing.
<small>Hard to say.</small>
</dd>
</dl>
<p>
Return value of <code>requestHandler</code> is a tuple containing a mime-type string
such as <samp>"image/png"</samp> and a complete byte string representing the
rendered tile.
</p>
<p>
See
<a href="http://tilestache.org/doc/TileStache.html#-requestHandler">TileStache.requestHandler</a>
documentation for more information.
</p>
<h2><a id="serving-tiles" name="serving-tiles">Serving Tiles</a></h2>
<p>
We currently provide three scripts for serving tiles: one for a WSGI-based
webserver, one for a CGI-based webserver, and one for Apache <code>mod_python</code>.
</p>
<h4><a id="wsgi" name="wsgi">WSGI</a></h4>
<p>
TileStache comes with a WSGI application and a
<a href="http://werkzeug.pocoo.org/">Werkzeug</a> web server. To use the
built-in server, run <tt>tilestache-server.py</tt>,
which (by default) looks for a config file named <tt>tilestache.cfg</tt>
in the current directory and then serves tiles on
<tt>http://127.0.0.1:8080/</tt>. Check <tt>tilestache-server.py --help</tt>
to change these defaults.
</p>
<p>Alternatively, any WSGI server can be pointed at an instance of
<tt>TileStache.WSGITileServer</tt>. Here’s how to use it with
<a href="http://gunicorn.org/">gunicorn</a>:
</p>
<pre>
$ gunicorn "TileStache:WSGITileServer('/path/to/tilestache.cfg')"
</pre>
<p>
See
<a href="http://tilestache.org/doc/TileStache.html#WSGITileServer"><code>TileStache.WSGITileServer</code></a>
documentation for more information.
</p>
<h4><a id="cgi" name="cgi">CGI</a></h4>
<p>
Using TileStache through CGI supports basic tile serving, and is useful for
simple testing and low-to-medium traffic websites. This is a complete, working
CGI script that looks for configuration in a local file called
<tt>tilestache.cfg</tt>:
</p>
<pre>
#!/usr/bin/python
import os, TileStache
TileStache.cgiHandler(os.environ, 'tilestache.cfg', debug=True)
</pre>
<p>
See
<a href="http://tilestache.org/doc/TileStache.html#-cgiHandler"><code>TileStache.cgiHandler</code></a>
documentation for more information.
</p>
<h4><a id="mod-python" name="mod-python">mod_python</a></h4>
<p>
Using TileStache through <code>mod_python</code> improves performance by
caching imported modules, but must be configured via the Apache webserver
config. This is a complete example configuration for a webserver publishing
tiles configured by a file in <code>/etc</code>:
</p>
<pre>
<Directory /var/www/tiles>
AddHandler mod_python .py
PythonHandler TileStache::modpythonHandler
PythonOption config /etc/tilestache.cfg
</Directory>
</pre>
<p>
See
<a href="http://tilestache.org/doc/TileStache.html#-modPythonHandler"><code>TileStache.modPythonHandler</code></a>
documentation for more information.
</p>
<h2><a id="configuring-tilestache" name="configuring-tilestache">Configuring TileStache</a></h2>
<p>
TileStache configuration is stored in JSON files, and is composed of two main
top-level sections: <samp>"cache"</samp> and <samp>"layers"</samp>. There are
examples of both in this minimal sample configuration:
</p>
<pre>
{
"cache": {"name": "Test"},
"layers": {
"ex": {
"provider": {"name": "mapnik", "mapfile": "style.xml"},
"projection": "spherical mercator"
}
}
}
</pre>
<h3><a id="caches" name="caches">Caches</a></h3>
<p>
A Cache is the part of TileStache that stores static files to speed up future
requests. A few default caches are shown here, with additional cache classes
defined in
<a href="http://tilestache.org/doc/TileStache.Goodies.Caches.html"><code>TileStache.Goodies.Caches</code></a>
</p>
<h4><a id="test-cache" name="test-cache">Test</a></h4>
<p>
Simple cache that doesn’t actually cache anything.
</p>
<p>
Activity is optionally logged, though.
</p>
<p>
Example configuration:
</p>
<pre>
<span class="bg">{</span>
"cache": {
"name": "Test",
"verbose": True
}<span class="bg">,
"layers": { … }
}</span>
</pre>
<p>
Test cache parameters:
</p>
<dl>
<dt>verbose</dt>
<dd>
Optional boolean flag to write cache activities to a logging function,
defaults to <samp>False</samp> if omitted.
</dd>
</dl>
<p>
See
<a href="http://tilestache.org/doc/TileStache.Caches.html#Test">TileStache.Caches.Test</a>
documentation for more information.
</p>
<h4><a id="disk-cache" name="disk-cache">Disk</a></h4>
<p>
Caches files to disk.
</p>
<p>
Example configuration:
</p>
<pre>
<span class="bg">{</span>
"cache": {
"name": "Disk",
"path": "/tmp/stache",
"umask": "0000",
"dirs": "portable",
"gzip": ["xml", "json"]
}<span class="bg">,
"layers": { … }
}</span>
</pre>
<p>
Disk cache parameters:
</p>
<dl>
<dt>path</dt>
<dd>
Required local directory path where files should be stored.
</dd>
<dt>umask</dt>
<dd>
Optional string representation of octal permission mask for stored files.
Defaults to <samp>"0022"</samp>.
</dd>
<dt>dirs</dt>
<dd>
Optional string saying whether to create cache directories that are safe or
portable. For an example tile <samp>12/656/1582.png</samp>,
<samp>"portable"</samp> creates matching directory trees while
<samp>"safe"</samp> guarantees directories with fewer files, e.g.
<samp>12/000/656/001/582.png</samp>. Defaults to <samp>"safe"</samp>.
</dd>
<dt>gzip</dt>
<dd>
Optional list of file formats that should be stored in a
compressed form. Defaults to <samp>["txt", "text", "json", "xml"]</samp>.
Provide an empty list in the configuration for no compression.
</dd>
</dl>
<p>
If your configuration file is loaded from a remote location, e.g.
<samp>http://example.com/tilestache.cfg</samp>, the path <strong>must</strong>
be an unambiguous filesystem path, e.g. <samp>"file:///tmp/cache"</samp>.
</p>
<p>
See
<a href="http://tilestache.org/doc/TileStache.Caches.html#Disk">TileStache.Caches.Disk</a>
documentation for more information.
</p>
<h4><a id="multi-cache" name="multi-cache">Multi</a></h4>
<p>
Caches tiles to multiple, ordered caches.
</p>
<p>
Multi cache is well-suited for a speed-to-capacity gradient, for example a
combination of <a href="#memcache-cache">Memcache</a> and <a href="#s3-cache">S3</a>
to take advantage of the high speed of memcache and the high capacity of S3.
Each tier of caching is checked sequentially when reading from the cache, while
all tiers are used together for writing. Locks are only used with the first cache.
</p>
<p>
Example configuration:
</p>
<pre>
<span class="bg">{</span>
"cache": {
"name": "Multi",
"tiers": [
{
"name": "Memcache",
"servers": ["127.0.0.1:11211"]
},
{
"name": "Disk",
"path": "/tmp/stache"
}
]
}<span class="bg">,
"layers": { … }
}</span>
</pre>
<p>
Multi cache parameters:
</p>
<dl>
<dt>tiers</dt>
<dd>
Required list of cache configurations. The fastest, most local cache should
be at the beginning of the list while the slowest or most remote cache
should be at the end. Memcache and S3 together make a great pair.
</dd>
</dl>
<p>
See
<a href="http://tilestache.org/doc/TileStache.Caches.html#Multi">TileStache.Caches.Multi</a>
documentation for more information.
</p>
<h4><a id="memcache-cache" name="memcache-cache">Memcache</a></h4>
<p>
Caches tiles to <a href="http://memcached.org/">Memcache</a>,
requires <a href="http://www.tummy.com/Community/software/python-memcached/">python-memcached</a>.
</p>
<p>
Example configuration:
</p>
<pre>
<span class="bg">{</span>
"cache": {
"name": "Memcache",
"servers": ["127.0.0.1:11211"],
"revision": 0
}<span class="bg">,
"layers": { … }
}</span>
</pre>
<p>
Memcache cache parameters:
</p>
<dl>
<dt>servers</dt>
<dd>
Optional array of servers, list of <samp>"{host}:{port}"</samp> pairs.
Defaults to <samp>["127.0.0.1:11211"]</samp> if omitted.
</dd>
<dt>revision</dt>
<dd>
Optional revision number for mass-expiry of cached tiles regardless of lifespan.
Defaults to <samp>0</samp>.
</dd>
</dl>
<p>
See
<a href="http://tilestache.org/doc/TileStache.Memcache.html#Cache">TileStache.Memcache.Cache</a>
documentation for more information.
</p>
<h4><a id="s3-cache" name="s3-cache">S3</a></h4>
<p>
Caches tiles to <a href="https://s3.amazonaws.com/">Amazon S3</a>,
requires <a href="http://pypi.python.org/pypi/boto">boto</a> (2.0+).
</p>
<p>
Example configuration:
</p>
<pre>
<span class="bg">{</span>
"cache": {
"name": "S3",
"bucket": "<bucket name>",
"access": "<access key>",
"secret": "<secret key>"
}<span class="bg">,
"layers": { … }
}</span>
</pre>
<p>
S3 cache parameters:
</p>
<dl>
<dt>bucket</dt>
<dd>
Required bucket name for S3. If it doesn’t exist, it will be created.
</dd>
<dt>access</dt>
<dd>
Required access key ID for your S3 account. You can find this under “Security
Credentials” at your <a href="http://aws.amazon.com/account/">AWS account page</a>.
</dd>
<dt>secret</dt>
<dd>
Required secret access key for your S3 account. You can find this under “Security
Credentials” at your <a href="http://aws.amazon.com/account/">AWS account page</a>.
</dd>
</dl>
<p>
See
<a href="http://tilestache.org/doc/TileStache.S3.html#Cache">TileStache.S3.Cache</a>
documentation for more information.
</p>
<h4><a id="additional-caches" name="additional-caches">Additional Caches</a></h4>
<p>
New caches with functionality that’s not strictly core to TileStache first appear in
<a href="http://tilestache.org/doc/TileStache.Goodies.Caches.html">TileStache.Goodies.Caches</a>.
</p>
<h5>LimitedDisk</h5>
<p>
Cache that stores a limited amount of data. This is an example cache that uses
a SQLite database to track sizes and last-read times for cached tiles, and
removes least-recently-used tiles whenever the total size of the cache exceeds
a set limit. See
<a href="http://tilestache.org/doc/TileStache.Goodies.Caches.LimitedDisk.html">TileStache.Goodies.Caches.LimitedDisk</a>
for more information.
</p>
<h3><a id="layers" name="layers">Layers</a></h3>
<p>
A Layer represents a set of tiles in TileStache. It keeps references to
providers, projections, a Configuration instance, and other details required
for to the storage and rendering of a tile set.
</p>
<p>
Example layer configuration:
</p>
<pre>
<span class="bg">{
"cache": …,
"layers":
{</span>
"example-name":
{
"provider": { … },
"metatile": { … },
"preview": { … },
"stale lock timeout": …,
"cache lifespan": …,
"projection": …,
"write cache": …,
"allowed origin": …,
"jpeg options": …,
"png options": …
}
<span class="bg">}
}</span>
</pre>
<p>
The public-facing URL of a single tile for this layer might look like this:
</p>
<pre>
http://example.com/tilestache.cgi/example-name/0/0/0.png
</pre>
<p>
Shared layer parameters:
</p>
<dl>
<dt>provider</dt>
<dd>
Refers to a Provider, explained in detail under
<a href="#providers">Providers</a>.
</dd>
<dt>metatile</dt>
<dd>
Optionally makes it possible for multiple individual tiles to be rendered
at one time, for greater speed and efficiency. This is commonly used for
bitmap providers such as Mapnik. See <a href="#metatiles">Metatiles</a>
for more information.
</dd>
<dt>preview</dt>
<dd>
Optionally overrides the starting point for the built-in per-layer slippy
map preview, useful for image-based layers where appropriate. See
<a href="#preview">Preview</a> for more information.
</dd>
<dt>projection</dt>
<dd>
Names a geographic projection, explained in
<a href="#projections">Projections</a>. If omitted, defaults to
<samp>"spherical mercator"</samp>.
</dd>
<dt>stale lock timeout</dt>
<dd>
An optional number of seconds to wait before forcing a lock that might be
stuck. This is defined on a per-layer basis, rather than for an entire
cache at one time, because you may have different expectations for the
rendering speeds of different layer configurations. Defaults to
<samp>15</samp>.
</dd>
<dt>cache lifespan</dt>
<dd>
An optional number of seconds that cached tiles should be stored. This is
defined on a per-layer basis. Defaults to forever if <samp>None</samp>,
<samp>0</samp> or omitted.
</dd>
<dt>write cache</dt>
<dd>
An optional boolean value to allow skipping cache write altogether.
This is defined on a per-layer basis. Defaults to true if omitted.
</dd>
<dt>allowed origin</dt>
<dd>
An optional string that shows up in the response HTTP header
<a href="http://www.w3.org/TR/cors/#access-control-allow-origin-response-hea">Access-Control-Allow-Origin</a>,
useful for when you need to provide javascript direct access to response
data such as GeoJSON or pixel values. The header is part of a
<a href="http://www.w3.org/TR/cors/">W3C working draft</a>.
Pro-tip: if you want to allow maximum permissions and minimal
security headache, use a value of <samp>"*"</samp> for this.
</dd>
<dt>jpeg options</dt>
<dd>
An optional dictionary of JPEG creation options, passed through
<a href="http://www.pythonware.com/library/pil/handbook/format-jpeg.htm">to PIL</a>.
Valid options include <var>quality</var> (integer), <var>progressive</var>
(boolean), and <var>optimize</var> (boolean).
</dd>
<dt>png options</dt>
<dd>
An optional dictionary of PNG creation options, passed through
<a href="http://www.pythonware.com/library/pil/handbook/format-png.htm">to PIL</a>.
Valid options include <var>palette</var> (URL or filename) and
<var>optimize</var> (boolean).
</dd>
</dl>
<h3><a id="providers" name="providers">Providers</a></h3>
<p>
A Provider is the part of TileStache that stores static files to speed up
future requests. A few default providers are shown here, with additional
provider classes defined in
<a href="http://tilestache.org/doc/TileStache.Goodies.Providers.html"><code>TileStache.Goodies.Providers</code></a>
</p>
<h4><a id="mapnik-provider" name="mapnik-provider">Mapnik</a></h4>
<p>
Built-in Mapnik provider, renders map images from Mapnik XML files.
</p>
<p>
Example Mapnik provider configuration:
</p>
<pre>
<span class="bg">{
"cache": { … }.
"layers":
{
"roads":
{</span>
"provider":
{
"name": "mapnik",
"mapfile": "style.xml"
}
<span class="bg">}
}
}</span>
</pre>
<p>
Mapnik provider parameters:
</p>
<dl>
<dt>mapfile</dt>
<dd>
Required local file path to Mapnik XML file.
</dd>
</dl>
<p>
See
<a href="http://tilestache.org/doc/TileStache.Providers.html#Mapnik">TileStache.Providers.Mapnik</a>
for more information.
</p>
<h4><a id="proxy-provider" name="proxy-provider">Proxy</a></h4>
<p>
Proxy provider, to pass through and cache tiles from other places.
</p>
<p>
Example Proxy provider configuration:
</p>
<pre>
<span class="bg">{
"cache": { … }.
"layers":
{
"roads":
{</span>
"provider":
{
"name": "proxy",
"url": "http://tile.openstreetmap.org/{Z}/{X}/{Y}.png"
}
<span class="bg">}
}
}</span>
</pre>
<p>
Proxy provider parameters:
</p>
<dl>
<dt>url</dt>
<dd>
Optional URL template for remote tiles, for example:
<samp>"http://tile.openstreetmap.org/{Z}/{X}/{Y}.png"</samp>
</dd>
<dt>provider</dt>
<dd>
Optional provider name string from Modest Maps built-ins. See
<code>ModestMaps.builtinProviders.keys()</code> for a list. Example:
<samp>"OPENSTREETMAP"</samp>.
</dd>
</dl>
<p>
See
<a href="http://tilestache.org/doc/TileStache.Providers.html#Proxy">TileStache.Providers.Proxy</a>
for more information.
</p>
<h4><a id="vector-provider" name="vector-provider">Vector</a></h4>
<p>
Provider that returns vector representation of features in a data source.
</p>
<p>
Currently two serializations and three encodings are supported for a total
of six possible kinds of output with these tile name extensions:
</p>
<dl>
<dt>GeoJSON (<samp>.geojson</samp>)</dt>
<dd>
Conforms to the <a href="http://geojson.org/geojson-spec.html">GeoJSON specification</a>.
</dd>
<dt>Arc GeoServices JSON (<samp>.arcjson</samp>)</dt>
<dd>
Conforms to ESRI’s <a href="http://www.esri.com/library/whitepapers/pdfs/geoservices-rest-spec.pdf">GeoServices REST specification</a>.
</dd>
<dt>GeoBSON (<samp>.geobson</samp>) and Arc GeoServices BSON (<samp>.arcbson</samp>)</dt>
<dd>
<a href="http://bsonspec.org/#/specification">BSON-encoded</a> GeoJSON and Arc JSON.
</dd>
<dt>GeoAMF (<samp>.geoamf</samp>) and Arc GeoServices AMF (<samp>.arcamf</samp>)</dt>
<dd>
<a href="http://opensource.adobe.com/wiki/download/attachments/1114283/amf0_spec_121207.pdf">AMF0-encoded</a> GeoJSON and Arc JSON.
</dd>
</dl>
<p>
Example Vector provider configurations:
</p>
<pre>
<span class="bg">{
"cache": { … }.
"layers":
{
"vector-postgis-points":
{</span>
"provider": {"name": "vector", "driver": "PostgreSQL",
"parameters": {"dbname": "geodata", "user": "geodata",
"table": "planet_osm_point"}}
<span class="bg">},
"vector-shapefile-lines":
{</span>
"provider": {"name": "vector", "driver": "shapefile",
"parameters": {"file": "oakland-uptown-line.latlon.shp"},
"properties": {"NAME": "name", "HIGHWAY": "highway"}}
<span class="bg">},
"vector-sf-streets":
{</span>
"provider": {"name": "vector", "driver": "GeoJSON",
"parameters": {"file": "stclines.json"},
"properties": ["STREETNAME"]}
<span class="bg">}
}
}</span>
</pre>
<p>
Vector provider parameters:
</p>
<dl>
<dt>driver</dt>
<dd>
String used to identify an OGR driver. Currently, only
<samp>"ESRI Shapefile"</samp>, <samp>"PostgreSQL"</samp>, and
<samp>"GeoJSON"</samp> are supported as data source drivers, with
<samp>"postgis"</samp> and <samp>"shapefile"</samp> accepted as
synonyms. Not case-sensitive.
</dd>
<dt>parameters</dt>
<dd>
Dictionary of parameters for each driver.
<br>
<dl>
<dt>PostgreSQL</dt>
<dd>
<samp>"dbname"</samp> parameter is required, with name of database.
<samp>"host"</samp>, <samp>"user"</samp>, and <samp>"password"</samp>
are optional connection parameters. One of <samp>"table"</samp> or
<samp>"query"</samp> is required, with a table name in the first case
and a complete SQL query in the second.
</dd>
<dt>Shapefile and GeoJSON</dt>
<dd>
<samp>"file"</samp> parameter is required, with filesystem path to
data file.
</dd>
</dl>
</dd>
<dt>properties</dt>
<dd>
Optional list or dictionary of case-sensitive output property names.
<br>
If omitted, all fields from the data source will be included in response.
If a list, treated as a whitelist of field names to include in response.
If a dictionary, treated as a whitelist and re-mapping of field names.
</dd>
<dt>clipped</dt>
<dd>
Default is <samp>true</samp>.