Common request parameters

Version parameter

The VERSION parameter specifies the protocol version number. Please refer to Version numbering and negotiation.

Request parameter

The REQUEST parameter indicates which service operation is being invoked.

Bounding box

BBOX is a shorthand representation of the very common a bounding box filter

The Bounding Box (BBOX) is a set of four comma-separated decimal, scientific notation, or certificates. These values specify the minimum X, minimum Y, maximum X, and maximum Y ranges, in that order, expressed in units of the SRS of the feature type(s) being queried.

A Bounding Box should not have zero area.

If a request contains an invalid Bounding Box (e.g., one whose minimum X is greater than or equal to the maximum X, or whose minimum Y is greater than or equal to the maximum Y) the server must throw an exception.

If a request contains a Bounding Box whose area does not overlap at all with the LatLongBoundingBox(s) advertised in the Capabilities XML for the requested geodata object, the server should return empty content (e.g. null feature set) for that element. Any elements that are partly or entirely contained in the Bounding Box should be returned in the appropriate format.

The SRS of the bounding box must be the same as the SRS of the feature type(s) in a request. The SRS of a feature type is advertised by a WFS in the capabilities document. If more than one feature type is specified in a request, the feature types must all be in the same SRS and the BBOX must be specified in the common SRS as well.

If the Bounding Box values are not defined for the given SRS (e.g., latitudes greater than 90 degrees in EPSG:4326), the server should return empty content for areas outside the valid range of the SRS.

In the particular case of longitude, the following behavior applies regarding the anti-meridian at 180 degrees of longitude. There is a legitimate desire for maps that span the anti-meridian (for example, a map centered on the Pacific Ocean). If Xmin is the west-most longitude in degrees and Xmax is the east-most, then the following constraint applies:

-180 <= Xmin < Xmax < 540

Xmin,Xmax values and the corresponding scope of the bounding box:

-180,180 = Earth centered at Greenwich

0,360 = Earth with Greenwich at left edge

120,250 = Pacific Ocean

Vendor-specific parameters

Requests may allow for optional vendor-specific parameters (VSPs) that will enhance the results of a request. Typically, these are used for private testing of non-standard functionality prior to possible standardization. A generic client is not required or expected to make use of these VSPs.

An OGC Web Service must produce a valid result when:

• VSPs are missing or malformed (i.e., the Service shall supply a default value)

• VSPs are supplied that are not known to the Service (i.e., the Service shall ignore unknown request parameters)

An OGC Web Service may choose not to advertise some or all of its VSPs. If VSPs are included in the Capabilities XML, the VendorSpecificCapabilities element must be redefined accordingly. Additional schema documents may be imported containing the redefinition of the element.

Clients may read the vendor specific definition from the capabilities schemas and formulate requests using any VSPs advertised therein.

Vendors should choose vendor-specific parameter names with care to avoid clashes with standard parameters.

Common parameters

The following table describes parameters common to all WFS requests.

Table 1 Common parameters for WFS requests