Martin Desruisseaux created SIS-593:
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Summary: Resolve auxiliary files relatively to GML or WKT file
providing parameter values
Key: SIS-593
URL: https://issues.apache.org/jira/browse/SIS-593
Project: Spatial Information Systems
Issue Type: Improvement
Components: Referencing
Reporter: Martin Desruisseaux
Assignee: Martin Desruisseaux
Fix For: 1.5
In the ISO 19111 {{ParameterValue}} class, values that are too complex for
being expressed as an {{int[]}}, {{double[]}} or {{String}} type may be encoded
in auxiliary files. It is the case, for example, of gridded data such as datum
shift grids. The name of an auxiliary file is given by
{{ParameterValue.valueFile}}, but often as a _relative_ path. The directory
where that file is located is unspecified by ISO 19111 and depends on the
operation using the parameter. For example, datum shift grids used by
coordinate transformations are searched by Apache SIS in the
{{$SIS_DATA/DatumChanges}} directory, where {{$SIS_DATA}} is the value of the
environment variable. However, the latest approach requires that all
potentially used auxiliary files are preexisting on the local machine. This
assumption may be applicable for parameters coming from a well-known registry
such as EPSG, but cannot work with arbitrary operations where the auxiliary
files need to be transferred together with the parameter values. For the latter
case, an alternative is to consider the auxiliary files as relative to the GML
document or WKT file that provides the parameter values. For allowing users to
resolve or download auxiliary files in that way, a {{getSourceFile()}} method
needs to be added to Apache SIS {{DefaultParameterValue}} class. Operations can
then use {{URI.resolve(URI)}} for getting the absolute path of an auxiliary
file from the same server or directory than the GML or WKT file of parameter
values.
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