I forgot to mention a point about the CRS WKT 2.0 meeting at OGC. They
were a discussion about how a parser shall behave when an unknown
keyword is found while parsing a WKT. The GDAL behaviour is to ignore
unknown keywords. The Geotk behaviour is to throw an exception. Both
approaches have pro-and-con, so this seems to be an example of situation
where business and scientific are having different goals.
My rational for throwing an exception is that the parser have no idea if
an unknown keyword is important or not. Maybe the unknown keyword
contains only metadata information that can be safely ignored. But maybe
the keyword contains information that affect the numerical values if
projected coordinates. For example the WKT 2.0 format is considering to
add some new UNIT keyword (in addition to the existing one). Ignoring
such keyword, then parsing the remainder of the WKT with the wrong unit,
will obviously produce wrong map projection.
Business wants their products to be tolerant to unexpected situations
and still produce some results, even if inaccurate. But scientists want
to trust their data and be aware of anything that may affect their
confidence. For a scientist, the worst thing that could happen is often
a program that seems to work but produce wrong results because of
unnoticed errors - it is better to stop the calculation rather than
letting unnoticeable errors to happen. But for some business, the
program shall not stop even if there is problems.
My personal point of view is to adopt the scientific approach as the
default one: be strict and throw an exception if the data are at risk of
being erroneous. But I admit that we will need to allow SIS to run in a
lenient mode if the user wants to. In Geotk that were some boolean flags
there-and-there for this purpose. For SIS, it may be worth to do some
consolidation about "what is strict, what is lenient" in some central
place...
Martin
