DAL Parameters in 3 factor semantics are uniquely defined by the triple of name, UCD , and unit. Data services are free to support as many such parameters as is appropriate for their datasets, in addition to supporting standard parameters. With the three factors, it is unlikely that two service providers will by accident use the same three factors for parameters of differing semantics.

With standard parameters as defined in this document, clients can rely on certain semantics and exploit that knowledge in the provision of special UIs or APIs.

Both standard and non-standard parameters should follow DALI conventions if at all possible. Roughly, float-valued target fields should be accessed or constrained via interval-valued parameters (i.e., do not split up minimum and maximum into separate parameters). Depending on their semantics, integer parameters should either be intervals or enumerated parameters (which typically can be repeated). Geometry fields should be accessed or constrained using geometry values (circle and polygon xtypes from DALI, following the examples of CIRCLE and POLYGON.