Features

There are currently three types of Feature providers:

• SQL: The features are stored in a SQL database (PostgreSQL/PostGIS, GeoPackage, SQLite/SpatiaLite).
• WFS: The features are retrieved from an OGC WFS.
• GraphQL: The features are retrieved from a GraphQL API. This Feature provider is experimental and has limitations..

Configuration

These are common configuration options for all provider types.

Name	Default	Description	Type	Since
id		Unique identifier of the entity, has to match the filename. Allowed characters are (A-Z, a-z), numbers (0-9), underscore and hyphen.	string	v2.0
providerType		Always FEATURE.	string	v2.0
providerSubType		SQL for SQL DBMS as data source, WFS for OGC Web Feature Service as data source.	string	v2.0
featureProviderType		Deprecated See providerSubType.	string	v2.0
nativeCrs	CRS84	Coordinate reference system of geometries in the dataset. The EPSG code of the coordinate reference system is given as integer in code. forceAxisOrder may be set to use a non-default axis order: LON_LAT uses longitude/east as first value and latitude/north as second value, LAT_LON uses the reverse. NONE uses the default axis order and is the default value. Example: The default coordinate reference system CRS84 would look like this: code: 4326 and forceAxisOrder: LON_LAT.	object	v2.0
nativeTimeZone	UTC	A timezone ID, such as Europe/Berlin. Is applied to temporal values without timezone in the dataset.	string	v2.0
typeValidation	NONE	Optional type definition validation with regard to the data source (only for SQL). NONE means no validation. With LAX the validation will fail and the provider will not start, when issues are detected that would definitely lead to runtime errors. Issues that might lead to runtime errors depending on the data will be logged as warning. With STRICT the validation will fail for any detected issue. That means the provider will only start if runtime errors with regard to the data source can be ruled out.	string	v2.0
extensions	[]	Definition of extensions, see Extensions.	array	v2.0
types	{}	Definition of feature types. The entries have to be schema definitions with type: OBJECT and at least one property with role: ID.	object	v2.0
fragments	{}	Definition of reusable schema fragments that can be referenced using schema in types. The entries are arbitrary schema definitions.	object	v2.0
auto	false	Option to derive types definitions automatically from the data source. When enabled types must not be set.	boolean	v2.0
autoPersist	false	Deprecated, use the editor instead. Option to persist definitions generated with auto to the configuration file. The Store must not be READ_ONLY for this to take effect.	boolean	v2.0
autoTypes	[]	Deprecated, use the editor instead. List of source types to include in derived types definitions when auto: true. Currently only works for SQL.	array	v2.0

Schema Definitions

Name	Default	Description	Type	Since
sourcePath		The relative path for this schema object. The syntax depends on the provider types, see SQL or WFS.	string	v2.0
path		Deprecated See sourcePath.	string	v2.0
sourcePaths	[sourcePath]	Deprected, use concat or coalesce instead. The relative paths for this schema object. The syntax depends on the provider types, see SQL or WFS.	array	v2.0
type	STRING/OBJECT	Data type of the schema object. Default is OBJECT when properties is set, otherwise it is STRING. Possible values: - FLOAT, INTEGER, STRING, BOOLEAN, DATETIME, DATE for simple values. - GEOMETRY for geometries. - OBJECT for objects. - OBJECT_ARRAY for a list of objects. - VALUE_ARRAY for a list of simple values. - FEATURE_REF for a reference to another feature or external resource. - FEATURE_REF_ARRAY for a list of references to others features or external resources.	string	v2.0
role	null	Indicates special meanings of the property. ID is to be specified at the property of an object to be used for the featureId in the API. This property is typically the first property in the properties object. Allowed characters in these properties are all characters except the space character (" ") and the horizontal bar ("/"). TYPE can be specified at the property of an object that contains the name of a subobject type. If an object type has multiple geometry properties, then specify PRIMARY_GEOMETRY at the property to be used for bbox queries and to be encoded in data formats with exactly one or a singled out geometry (e.g. in GeoJSON geometry). If an object type has multiple temporal properties, then PRIMARY_INSTANT should be specified at the property to be used for datetime queries, provided that a time instant describes the temporal extent of the features. If, on the other hand, the temporal extent is a time interval, then PRIMARY_INTERVAL_START and PRIMARY_INTERVAL_END should be specified at the respective temporal properties.	string	v2.0
valueType	STRING	Only needed when type is VALUE_ARRAY. Possible values: FLOAT, INTEGER, STRING, BOOLEAN, DATETIME, DATE	string	v2.0
geometryType	null	The specific geometry type for properties with type: GEOMETRY. Possible values are simple feature geometry types: POINT, MULTI_POINT, LINE_STRING, MULTI_LINE_STRING, POLYGON, MULTI_POLYGON, GEOMETRY_COLLECTION and ANY	string	v2.0
objectType		Optional name for an object type, used for example in JSON Schema. For properties that should be mapped as links according to RFC 8288, use Link.	string	v2.0
label		Label for the schema object, used for example in HTML representations.	string	v2.0
description		Description for the schema object, used for example in HTML representations or JSON Schema.	string	v2.0
unit		The unit of measurement of the value, only relevant for numeric properties.	string	v2.0
constantValue	null	Might be used instead of sourcePath to define a property with a constant value.	string	v2.0
scope	null	*Deprecated, use excludedScopes instead.* Optional scope for properties that should only be used when either reading (QUERIES) or writing (MUTATIONS) features.	string	v2.0
excludedScopes	[]	Optional exclusion of a property from a schema scope. See Schema Scopes for a description of the scopes.	array	v2.0
refType		For a property of type FEATURE_REF or FEATURE_REF_ARRAY where the target is always a feature of another type in the same provider, declare the feature type identifier in refType. For details see Feature References.	string	v2.0
refUriTemplate		For a property of type FEATURE_REF or FEATURE_REF_ARRAY where the target is an external resource, declare the URI template of the link in refUriTemplate. For details see Feature References.	string	v2.0
refKeyTemplate		For a property of type FEATURE_REF or FEATURE_REF_ARRAY where the type of the target varies, declare the string template of the foreign key in refKeyTemplate. For details see Feature References.	string	v2.0
schema	null	Reference to an external schema definition. The default resolver will resolve references to entries in fragments e.g. #/fragments/example. For additional resolvers see Extensions.	string	v2.0
ignore	false	Option to completely ignore this schema object. Main purpose is to ignore parts of schemas referenced with schema.	boolean	v2.0
transformations	[]	Optional transformations for the property, see transformations.	array	v2.0
constraints	{}	Optional description of schema constraints, especially for JSON schema generation. See Constraints.	object	v2.0
forcePolygonCCW	true	Option to disable enforcement of counter-clockwise orientation for exterior rings and a clockwise orientation for interior rings (only for SQL).	boolean	v2.0
linearizeCurves	false	Option to linearize curve geometries (e.g., CircularString or CurvePolygon) to a Simple Features geometry. This option only applies to SQL feature providers of dialect PostGIS.	boolean	v2.0
isQueryable	see description	Deprecated, use excludedScopes instead. Properties that are not of type OBJECT or OBJECT_ARRAY are by default eligible as queryables. This setting can be used to declare a property as ineligible, for example, if the property is not optimized for use in queries. If an eligible property can actually be queried is decided by the provider implementation, that might not be feasible due to technical reasons.	boolean	v2.0
isSortable	see description	Deprecated, use excludedScopes instead. Only the direct properties of a feature type that are of type STRING, FLOAT, INTEGER, DATE, or DATETIME are eligible as sortables. This setting can be used to declare a property as ineligible, for example, if the property is not optimized for use in queries. If an eligible property can actually be used as sortable is decided by the provider implementation, that might not be feasible due to technical reasons.	boolean	v2.0
isLastModified	see description	Identifies a DATETIME property as a property that contains the timestamp when the feature was last modified. This information is used in optimistic locking to evaluate the pre-conditions, if a mutation request includes a Last-Modified header.	boolean	v2.0
properties		Only for OBJECT and OBJECT_ARRAY. Object with the property names as keys and schema objects as values.	object	v2.0
merge	[]	If only some of the properties are defined in an external schema, or if some of the properties should be mapped to a different table, this provides a convenient way to define these properties alongside the regular properties. The option takes a list of schema objects, but only sourcePath, schema and properties are considered. For details see Mapping Operations.	array	v2.0
allOf	[]	Deprecated See merge.	array	v2.0
coalesce	[]	If the value for a property may come from more than one sourcePath, this allows to choose the first non-null value. This takes a list of value schemas, for details see Mapping Operations.	array	v2.0
concat	[]	If the values for an array property may come from more than one sourcePath, this allows to concatenate all available values. This takes a list of value or value array schemas, for details see Mapping Operations.	array	v2.0

Connection Info

For data source specifics, see SQL and WFS.

Example Configuration (SQL)

See the feature provider of the API Vineyards in Rhineland-Palatinate, Germany.

Mapping Operations

Mapping operations may be needed when the source and target schema structure diverge too much.

Merge

If only some of the properties are defined in an external schema, or if some of the properties should be mapped to a different table, this provides a convenient way to define these properties alongside the regular properties.

Examples

Define only some properties using an external JSON schema

example:
  sourcePath: /main
  type: OBJECT
  merge:
  - properties:
      id:
        sourcePath: id
        type: INTEGER
        role: ID
  - sourcePath: '[JSON]names'
    schema: names.json

Using columns from a joined table in the main feature

example:
  sourcePath: /main
  type: OBJECT
  merge:
  - properties:
      id:
        sourcePath: id
        type: INTEGER
        role: ID
  - sourcePath: '[id=id]names'
    properties:
      name1:
        sourcePath: name1
        type: STRING
      name2:
        sourcePath: name2
        type: STRING

Coalesce

If the value for a property may come from more than one sourcePath, this allows to choose the first non-null value.

Example

foo:
  type: OBJECT
  properties:
    bar:
      type: VALUE
      coalesce:
      - sourcePath: bar_stringValue
        type: STRING
      - sourcePath: bar_integerValue
        type: INTEGER
      - sourcePath: bar_booleanValue
        type: BOOLEAN

Type compatibility

Constraints on the types of inner properties depending on the type of the outer property are shown in the table below.

Outer type	Valid inner types	Remarks
VALUE	INTEGER, FLOAT, STRING, BOOLEAN, DATETIME, DATE
INTEGER	INTEGER
FLOAT	FLOAT
STRING	STRING
BOOLEAN	BOOLEAN
DATETIME	DATETIME
DATE	DATE
OBJECT	OBJECT	Different objectType with different schemas can be used
FEATURE_REF	FEATURE_REF	Different refType can be used

Concat

If the values for an array property may come from more than one sourcePath, this allows to concatenate all available values.

Example

foo:
  type: OBJECT
  properties:
    bar:
      type: FEATURE_REF_ARRAY
      concat:
      - sourcePath: '[id=foo_fk]baz1/id'
        refType: baz1
      - sourcePath: '[id=foo_fk]baz2/id'
        refType: baz2
      - sourcePath: '[id=foo_fk]bazn/id'
        refType: bazn

Type compatibility

Constraints on the types of inner properties depending on the type of the outer property are shown in the table below.

Outer type	Valid inner types	Remarks
VALUE_ARRAY	VALUE_ARRAY, INTEGER, FLOAT, STRING, BOOLEAN, DATETIME, DATE
OBJECT_ARRAY	OBJECT_ARRAY, OBJECT	Different objectType with different schemas can be used
FEATURE_REF_ARRAY	FEATURE_REF_ARRAY, FEATURE_REF	Different refType can be used

Feature References

Feature references (type FEATURE_REF or FEATURE_REF_ARRAY) are object properties with three pre-defined properties: id, title, and type.

• id is the foreign key, that is the ID property of a referenced feature, and is either a STRING or INTEGER.
• title is the title to use when presenting the link to a user, a STRING. The default value is the id, if the property is not specified.
• type is the feature type of the referenced feature in the same feature provider, a STRING.

Limitations: These properties do not support transformations (e.g. stringFormat) or coalesce.

Encoding feature references

When requested via the API, the feature reference can be encoded according to different profiles using the query parameter profile and depending on the negotiated feature format. The following profiles are supported:

• rel-as-key: the identifier of the feature in its collection (the featureId);
• rel-as-uri: the URI of the feature;
• rel-as-link: an object with two properties: href with the URI of the feature and title with a title of the feature.

The rel-as-link profile is typically not supported for feature formats that do not support object properties, e.g., CSV or FlatGeobuf. In HTML, a link is encoded as an <a> element, in GML using XLink attributes.

The profile is negotiated based on the requested profile (default is rel-as-link) and the supported profiles of the negotiated format based on the Accept header and the query parameter f.

Configuration

Simple Case

If the default value of title (that is, the id) is sufficient and the target features are in the same API and all in the same collection, the properties of the object do not need to be specified in the schema. It is sufficient to specify the following configuration property:

• sourcePath: The value with the id of the referenced feature.
• type: The type of the id, either STRING (the default) or INTEGER.
• refType: the identifier of the feature type / collection of the referenced feature.

In the following example, the abs column is the foreign key of the referenced feature in the abschnitteaeste feature type:

abs:
  sourcePath: abs
  type: FEATURE_REF
  label: Abschnitt/Ast
  description: 16-stellige Kennung des Abschnittes oder Astes
  refType: abschnitteaeste

In the next example, there are two columns (abs and ast) which are foreign keys of the referenced feature in the abschnitte or aeste feature type. Only one of the two values is set and the first value that is not null is used:

abs:
  type: FEATURE_REF
  label: Abschnitt/Ast
  description: 16-stellige Kennung des Abschnittes oder Astes
  coalesce:
  - sourcePath: abs
    refType: abschnitte
  - sourcePath: ast
    refType: aeste

Advanced Cases

If the title should differ from id, if the type of the referenced feature is determined from the data, or if the referenced resource is outside of the API, the properties of the feature reference are explicitly specified in the feature schema.

Example:

unfaelle:
  sourcePath: "[abs=abs]unfaelle_point"
  type: FEATURE_REF_ARRAY
  label: Unfälle
  description: Unfälle auf dem Abschnitt oder Ast
  properties:
    id:
      type: INTEGER
      sourcePath: fid
    title:
      type: STRING
      sourcePath: unfzeit
    type:
      type: STRING
      constantValue: unfaelle

In addition, the following configuration options can be specified:

• refKeyTemplate: the string template for the value in the rel-as-key profile. Parameters are id and type. The default is {{id}}, if type is constant, otherwise {{type}}::{{id}}.
• refUriTemplate: the string template of the URI of the referenced feature. Parameters are id, type, and apiUri (the URI of the landing page of the API). The default is {{apiUri}}/collections/{{type}}/items/{{id}}.

Example:

externalReferences:
  sourcePath: "[fk=oid]externalref"
  type: FEATURE_REF_ARRAY
  label: External References
  refUriTemplate: "https://example.com/foo/bar/{{type}}/{{id}}"
  refKeyTemplate: "{{type}}_{{id}}"
  properties:
  id:
    type: INTEGER
    sourcePath: oid
  title:
    type: STRING
    sourcePath: label
  type:
    type: STRING
    sourcePath: type