ARLAS-OGC-API

ARLAS offers an OGC API that makes the ARLAS catalog interoperable with GIS applications. The catalog is explorable through two standard endpoints:

• A WFS endpoint for each collection reference that provides access to the geographic features of the collection.
• A CSW endpoint to discover the available collections.

A third endpoint is available to get an Opensearch description of CSW service.

URL Schema

The table below lists the URL endpoints and their ogc "parameters". The parameters are separated with the character &.

PATH Template	Description
/arlas/ogc/wfs/{collection}?wfsParameters	Download the features of the given {collection}
/arlas/ogc/csw/?cswParameters	Discover the available collections in ARLAS
/arlas/ogc/csw/opensearch	OpenSearch CSW Description Document

URL Parameters

WFS Parameters

The following parameters are mandatory and must be specified for all WFS requests

Parameter	Description	Possible values
service	name of the service	WFS
version	Supported WFS standard version	2.0.0
request	The WFS operation to perform	Six possible values. Check the table below

The table below sums up the WFS operations supported by ARLAS-server

Operation	Description
GetCapabilities	Generates a metadata document describing the WFS service provided by ARLAS-server as well as valid WFS operations and parameters
DescribeFeatureType	Returns a description of feature types supported by WFS service
GetFeature	Returns a selection of features from the given {collection} including geometry and attribute values
GetPropertyValue	Fetches the value of a given feature property of the {collection}
ListStoredQueries	Returns the list of the stored queries of WFS server
DescribeStoredQueries	Returns a metadata document describing the stored queries of WFS server

According to the chosen operation, you can specify a set of parameters

request=GetCapabilities

You can specify a language parameter :

Parameter	Description	Possible values	Mandatory/Optional
language	Language of the metadata	One of the official languages of the European Community expressed in conformity with ISO 639-2	Optional

This parameter conforms to INSPIRE recommendations.

• If the requested language is contained in the list of supported languages, then natural language metadata elements are returned in the requested language.
• If the requested language is not supported by the WFS, then this parameter is ignored.

request=DescribeFeatureType

This operation gives information about the feature type before requesting the actual data.

Parameter	Description	Possible values	Mandatory/Optional
typenames	Name of the feature type to describe	Must contain the name of the {collection}	Optional

request=GetFeature

This operation returns a selection of features from the given {collection}.

You can specify pagination parameters :

Parameter	Description	Possible values	Mandatory/Optional
count	Maximum number of returned features	Integer	Optional
startindex	Index to start the search from	Integer	Optional

You can use stored queries :

Parameter	Description	Possible values	Mandatory/Optional
storedquery_id	Id of a storied query in WFS server.	urn:ogc:def:query:OGC-WFS::GetFeatureById	Optional
id	Id of a feature to query.	text	Mandatory if storedquery_id is specified

You can query data using the following parameters

Parameter	Description	Possible values	Mandatory/Optional
resourceid	Id of a feature to query.	text	Optional
bbox	A geographic extend used to query any feature having its centroid contained within it.	west, south, east, north	Optional
filter	A filter used to select features by evaluating an expression	Filter Encoding language 2.0.2 Reference	Optional
srsname	crs of the features	http://www.opengis.net/def/crs/epsg/0/4326, urn:ogc:def:crs:EPSG::4326	Optional
typenames	Name of the feature type to describe	Must contain the name of the {collection}	Optional

request=GetPropertyValue

This operation returns the value of a feature property.

You must specify the feature property :

Parameter	Description	Possible values	Mandatory/Optional
valueReference	Feature type property	text	Mandatory

You can specify pagination parameters :

Parameter	Description	Possible values	Mandatory/Optional
count	Maximum number of returned features	Integer	Optional
startindex	Index to start the search from	Integer	Optional

You can use stored queries :

Parameter	Description	Possible values	Mandatory/Optional
storedquery_id	Id of a storied query in WFS server.	urn:ogc:def:query:OGC-WFS::GetFeatureById	Optional
id	Id of a feature to query.	text	Mandatory if storedquery_id is specified

You can query data using the following parameters

Parameter	Description	Possible values	Mandatory/Optional
resourceid	Id of a feature to query.	text	Optional
bbox	A geographic extend used to query any feature having its centroid contained within it.	west, south, east, north	Optional
filter	A filter used to select features by evaluating an expression	Filter Encoding language 2.0.2 Reference	Optional
typenames	Name of the feature type to describe	Must contain the name of the {collection}	Optional

Note

• bbox and resourceid can't be used together
• bbox and filter can't be used together
• resourceid and filter can't be used together

CSW Parameters

The following parameters are mandatory and must be specified for all CSW requests

Parameter	Description	Possible values
service	name of the service	CSW
version	Supported CSW standard version	3.0.0
request	The CSW operation to perform	Three possible values. Check the table below

The table below sums up the CSW operations supported by ARLAS-server

Operation	Description
GetCapabilities	Generates a metadata document describing the CSW service provided by ARLAS-server as well as valid CSW operations and parameters
GetRecords	Returns collection references metadata and identifier
GetRecordById	Returns a specific collection reference metadata and identifier

According to the chosen operation, you can specify a set of parameters

request=GetCapabilities

You can specify a language parameter :

Parameter	Description	Possible values	Mandatory/Optional
language (1)	Language of the metadata	One of the official languages of the European Community expressed in conformity with ISO 639-2	Optional
sections	Specifies which parts of the GetCapabilities response to include	ServiceIdentification, ServiceProvider, OperationsMetadata, Filter_Capabilities, All	Optional

(1) This parameter conforms to INSPIRE recommendations.

• If the requested language is contained in the list of supported languages, then natural language metadata elements are returned in the requested language.
• If the requested language is not supported by the WFS, then this parameter is ignored.

request=GetRecords & request=GetRecordById

The following parameters are common to GetRecords and GetRecordById

You can specify pagination parameters :

Parameter	Description	Possible values	Mandatory/Optional
maxRecords	Maximum number of returned collections	Integer	Optional
startposition	Index to start the search from	Integer	Optional

You can choose which metadata to return :

Parameter	Description	Possible values	Mandatory/Optional
elementName	Metadata elements to return (1).	Comma separated metadata elements. For instance : title,subject.	Optional
elementSetName	Group of metada elements to return.	brief, summary (default) or full	Optional
typenames	Defines the level of details present in the result set.	Record, csw:Record or gmd:MD_Metadata	Optional

(1) Possible values of elementName are : title, abstract, identifier, subject, creator, publisher, contributor, type, format, source, language, modified, boundingbox.

Note

• elementName and elementSetName can't be used together

You can choose the format :

Parameter	Description	Possible values	Mandatory/Optional
outputFormat	Whether to return response in application/xml or application/atom+xml format	application/xml (default), application/atom%2Bxml	Optional
outputSchema	The schema of output of GetRecords/GetRecordById response	http://www.opengis.net/cat/csw/3.0.0 (default) or http://www.isotc211.org/2005/gmd	Optional

You can query collection references metadata using the following parameters

Parameter	Description	Possible values	Mandatory/Optional
recordIds	Comma separated ids of collections	text	Optional
id	id of a collection	text	Mandatory for GetRecordById
q	Full text search on collection references	text	Optional
bbox	A geographic extend used to query any collection that intersects it.	west, south, east, north	Optional
constraint	A filter used to select collections references by evaluating an expression	Filter Encoding language 2.0.2 Reference	Optional
constraintLanguage	Language of the constraint	Filter	Optional

Note

• bbox and recordids can't be used together
• recordids and q can't be used together

Column filtering

A comma-separated list of columns can be passed in request header column-filter. Wildcards are supported.

A column filter stands for the fields that are available to a request body: - if a request body field doesn't belong to the column filter, a 403 is returned with the message The field '%s' isn't available or The fields '%s' aren't available; - only fields that belong to the column filter can be returned.

A column filter can be related to a collection, e.g. mycollection:myfield or it can be related to every collection, e.g. myfield. Trying to access a collection with no available field returns a 403. Collection names can be omitted or end with a '*'.

Examples of column-filter:

• mycollection:params.city,mycollection:params.country makes available params.city and params.country for collection mycollection
• mycollection*:params.city makes available params.city for all collections whose names start with mycollection
• params, params*, params.*, *params make available params.city, params.country, params.weight, and so on. for every collection
• params, :params, *:params make available params and subfields for every collection
• * makes all fields available
• *.* makes only subfields available, e.g. params.city and params.country but not id
• `` (empty value) makes all fields and collections forbidden.

If no column filter, then no filtering is done. An empty column filter will forbid all collections and columns.

The following OGC operations use this header:

Endpoint	Request	Filtering result
WFS	GetCapabilities	Return 403 if target collection is not available.
WFS	DescribeFeatureType	Only fields matching the filter will be returned. Return 403 if target collection is not available.
WFS	ListStoredQueries	Return 403 if target collection is not available.
WFS	DescribeStoredQueries	Return 403 if target collection is not available.
WFS	GetFeature	Only fields matching the filter will be returned. Return 403 if target collection is not available.
WFS	GetPropertyValue	Return 403 if target collection or column is not available.
CSW	GetCapabilities	Only collections matching the filter will be returned.
CSW	GetRecords	Only collections matching the filter will be returned.
CSW	GetRecordById	Return 403 if target collection or column is not available.