OBS_MetadataValidation doc

doc/measures_functions.md

@@ -108,7 +108,7 @@ The ```OBS_GetMeasure(polygon, measure_id)``` function returns any Data Observat
 Name |Description
 --- | ---
 polygon_geometry | a WGS84 polygon geometry (the_geom)
-measure_id | a measure identifier from the Data Observatory ([see available measures](https://cartodb.github.io/bigmetadata/observatory.pdf))  
+measure_id | a measure identifier from the Data Observatory ([see available measures](https://cartodb.github.io/bigmetadata/observatory.pdf))
 normalize | for measures that are **sums** (e.g. population) the default normalization is 'none' and response comes back as a raw value. Other options are 'denominator', which will use the denominator specified in the [Data Catalog](https://cartodb.github.io/bigmetadata/index.html) (optional)
 boundary_id | source of geometries to pull measure from (e.g., 'us.census.tiger.census_tract')
 time_span | time span of interest (e.g., 2010 - 2014)
@@ -143,7 +143,7 @@ The ```OBS_GetMeasureById(geom_ref, measure_id, boundary_id)``` function returns
 Name |Description
 --- | ---
 geom_ref | a geometry reference (e.g., a US Census geoid)
-measure_id | a measure identifier from the Data Observatory ([see available measures](https://cartodb.github.io/bigmetadata/observatory.pdf))  
+measure_id | a measure identifier from the Data Observatory ([see available measures](https://cartodb.github.io/bigmetadata/observatory.pdf))
 boundary_id | source of geometries to pull measure from (e.g., 'us.census.tiger.census_tract')
 time_span (optional) | time span of interest (e.g., 2010 - 2014). If `NULL` is passed, the measure from the most recent data will be used.
 
@@ -215,7 +215,7 @@ extent | A geometry of the extent of the input geometries
 metadata | A JSON array composed of metadata input objects.  Each indicates one desired measure for an output column, and optionally additional parameters about that column
 num_timespan_options | How many historical time periods to include.  Defaults to 1
 num_score_options | How many alternative boundary levels to include.  Defaults to 1
-target_geoms | Target number of geometries.  Boundaries with close to this many objects within `extent` will be ranked highest. 
+target_geoms | Target number of geometries.  Boundaries with close to this many objects within `extent` will be ranked highest.
 
 The schema of the metadata input objects are as follows:
 
@@ -321,6 +321,60 @@ SELECT OBS_GetMeta(
 ) FROM tablename
 ```
 
+## OBS_MetadataValidation(extent geometry, geometry_type text, metadata json, target_geoms)
+
+The ```OBS_MetadataValidation``` function peforms a validation check over
+the known issues using the extent, type of geometry and metadata we're going
+to use in the ```OBS_GetMeta``` function.
+
+#### Arguments
+
+Name | Description
+---- | -----------
+extent | A geometry of the extent of the input geometries
+geometry_type | The geometry type of the source data.
+metadata | A JSON array composed of metadata input objects.  Each indicates one desired measure for an output column, and optionally additional parameters about that column
+target_geoms | Target number of geometries.  Boundaries with close to this many objects within `extent` will be ranked highest.
+
+The schema of the metadata input objects are as follows:
+
+Metadata Input Key | Description
+--- | -----------
+numer_id | The identifier for the desired measurement.  If left blank, but a `geom_id` is specified, the column will return a geometry instead of a measurement.
+geom_id | Identifier for a desired geographic boundary level to use when calculating measures.  Will be automatically assigned if undefined.  If defined but `numer_id` is blank, then the column will return a geometry instead of a measurement.
+normalization | The desired normalization.  One of 'area', 'prenormalized', or 'denominated'.  'Area' will normalize the measure per square kilometer, 'prenormalized' will return the original value, and 'denominated' will normalize by a denominator.  Ignored if this metadata object specifies a geometry.
+denom_id | Identifier for a desired normalization column in case `normalization` is 'denominated'.  Will be automatically assigned if necessary.  Ignored if this metadata object specifies a geometry.
+numer_timespan | The desired timespan for the measurement.  Defaults to most recent timespan available if left unspecified.
+geom_timespan | The desired timespan for the geometry.  Defaults to timespan matching numer_timespan if left unspecified.
+target_area | Instead of aiming to have `target_geoms` in the area of the geometry passed as `extent`, fill this area.  Unit is square degrees WGS84.  Set this to `0` if you want to use the smallest source geometry for this element of metadata, for example if you're passing in points.
+target_geoms | Override global `target_geoms` for this element of metadata
+max_timespan_rank | Only include timespans of this recency (for example, `1` is only the most recent timespan). No limit by default
+max_score_rank | Only include boundaries of this relevance (for example, `1` is the most relevant boundary).  Is `1` by default
+
+#### Returns
+
+Key | Description
+--- | -----------
+valid | A boolean field that represents if the validation was succesful or not
+errors | A text array with all the possible errors.
+
+#### Examples
+
+Validate metadata with two additional column of US census
+data, using a boundary relevant for the geometry provided and latest timespan.
+Limit to only the most recent column most relevant to the extent & density of
+input geometries in `tablename`.
+
+```SQL
+SELECT OBS_MetadataValidation(
+  ST_SetSRID(ST_Extent(the_geom), 4326),
+  ST_GeometryType(the_geom),
+  '[{"numer_id": "us.census.acs.B01003001"}, {"numer_id": "us.census.acs.B01001002"}]',
+  COUNT(*)::INTEGER
+) FROM tablename
+GROUP BY ST_GeometryType(the_geom)
+```
+
 ## OBS_GetData(geomvals array[geomval], metadata json)
 
 The ```OBS_GetData(geomvals, metadata)``` function returns a measure and/or