Some end points of the DD-GRID-API specify the query parameter “filter”. This parameter is meant to offer a generic filtering mechanism. An example of such a filter is: only select one or more realizations from an ensemble run. In addition systems may offer more filter options.
However, implementing this filter query parameter is optional. Systems may decide to not implement it.
The generic syntax for the query parameter filter is:
../some-end-point?filter=attribute:comparer:value
The query parameter filter can (and often will) be used in combination with other query parameters.
This is a mandatory filter, that has to be implemented by every system that offers the DD-GRID-API.
Examples:
/coverages/ijsselmeer-prediction-2020-12-08/data?filter=realization:eq:16&quantity=waterlevel
/coverages/ijsselmeer-prediction-2020-12-08/data?filter=realization:in:[1,7,8,9,15]&quantity=tempature
/coverages/ijsselmeer-pdf-2020-12-08/data?filter=realization:in:[minimum,maximum]&x=6.984&y=53.
If no filtering on ensemble member(s) is requested, the data of all ensemble members will be returned. (The ensemble member identifiers will be an extra dimension in the netcdf file.)
An optional filter that systems might implement is selection on analysis time, i.e. the time stamp on which a computation was performed
Example:
/coverages?filter=analysisstarttime:eq:2020-07-18T00:00:00Z,analysisendtime:eq:2020-07-19T00:00:00Z&quantity=waterlevel_