Hello all
In the process of reading a Well Known Text (WKT), some non-fatal
warnings may happen (this email ignores fatal errors, which throw
exception without logging anything). Examples of warnings are:
* A metadata depends on an optional module which is not on the
classpath (example: TimeExtent).
* An unknown keyword has been found. The WKT specification requires
that we ignore unknown keywords (in order to allow users to extend
the WKT with their own elements, for example triaxal ellipsoids
[1]), but suggests that we emit a warning.
* An inconsistency is found. The specification said "In the event of
conflict in values given in the CRS WKT string and given by an
authority through an object’s name or an identifier, reading
software should throw an exception or give users a warning message.
The WKT values should be assumed to prevail." [2]
An example of warning message currently produced by the WKT parser is
(advises about rewording the warning are welcome):
Parsing of “WGS 84” done, but some elements were ignored.
• The text contains unknown elements:
‣ “MYEXT” in PRIMEM, GEOGCS.
What should be the policy about non-fatal warnings in Apache SIS? The
current approach is:
* When using the WKTFormat object (which give maximum control on WKT
parsing and formatting), no warnings are logged. But a getWarnings()
method is provided, which allow users to decide what they want to do
[3].
* When using the CRS.fromWKT(String) static convenience method [4],
currently warnings are ignored.
Should non-fatal warnings be logged when using a static convenience
method? If yes, should it be at Level.WARNING or at another lever?
Martin
[1] http://docs.opengeospatial.org/is/12-063r5/12-063r5.html#146
[2] http://docs.opengeospatial.org/is/12-063r5/12-063r5.html#139
[3]
https://builds.apache.org/job/sis-dev/javadoc/org/apache/sis/io/wkt/Warnings.html
[4]
https://builds.apache.org/job/sis-dev/javadoc/org/apache/sis/referencing/CRS.html#fromWKT-java.lang.String-
