Add map config extension for analyses

docs/MapConfig-Analyses-extension.md

@@ -0,0 +1,93 @@
+# 1. Purpose
+
+This specification describes an extension for
+[MapConfig 1.4.0](https://github.com/CartoDB/Windshaft/blob/master/doc/MapConfig-1.4.0.md) version.
+
+
+# 2. Changes over specification
+
+This extension targets layers with `sql` option, including layer types: `cartodb`, `mapnik`, and `torque`.
+
+It extends MapConfig with a new attribute: `analyses`.
+
+## 2.1 Analyses attribute
+
+The new analyses attribute must be an array of analyses as per [camshaft](https://github.com/CartoDB/camshaft). Each
+analysis must adhere to the [camshaft-reference](https://github.com/CartoDB/camshaft/blob/0.8.0/reference/versions/0.7.0/reference.json) specification.
+
+Each node can have an id that can be later references to consume the query from MapConfig's layers.
+
+Basic analyses example:
+
+```javascript
+[
+    {
+        // REQUIRED
+        // string, `id` free identifier that can be reference from any layer
+        "id": "HEAD",
+        // REQUIRED
+        // string, `type` camshaft's analysis type
+        "type": "source",
+        // REQUIRED
+        // object, `params` will depend on `type`, check camshaft-reference for more information
+        "params": {
+            "query": "select * from your_table"
+        }
+    }
+]
+```
+
+# 2.2. Integration with layers
+
+As pointed before an analysis node id can be referenced from layers to consume its output query.
+
+The layer consuming the output must reference it with the following option:
+
+```
+{
+    "options": {
+        // REQUIRED
+        // object, `source` as in the future we might want to have other source options
+        "source": {
+            // REQUIRED
+            // string, `id` the analysis node identifier
+            "id": "HEAD"
+        }
+    }
+}
+```
+
+## 2.3. Complete example
+
+```
+{
+    "version": "1.4.0",
+    "layers": [
+        {
+            "type": "cartodb",
+            "options": {
+                "source": {
+                    "id": "HEAD"
+                },
+                "cartocss": "...",
+                "cartocss_version": "2.3.0"
+            }
+        }
+    ],
+    "analyses": [
+        {
+            "id": "HEAD",
+            "type": "source",
+            "params": {
+                "query": "select * from your_table"
+            }
+        }
+    ]
+}
+```
+
+# History
+
+## 1.0.0
+
+ - Initial version