Hi edgar soldin wrote: > what attribute types are used in common GIS software? > do they limit the choices or rather support many, albeit the lot is probably > represented by few internally? > > Jukka, what do you have to say?
I believe that the short list that is supported by shapefiles makes the base: date, string, Boolean, number, float However, I have feeling that OpenJUMP is not at all the only program that does not support Boolean type. I am not sure if dBase III of IV had support for that or has ESRI made some later extension. ESRI Geodatabase has a bit longer list: date, text, short integer, long integer, double, float (no Boolean, translates to integer) Both ESRI lists taken from http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?TopicName=How_data_converts_when_importing GDAL/OGR supports internally there attribute types: http://www.gdal.org/unionOGRField-members.html There is a new implementation about subtypes which brought for example support for Boolean attributes into GDAL by extending Integer http://trac.osgeo.org/gdal/wiki/rfc50_ogr_field_subtype The list of data types defined for the new OGC GeoPackage standard is in the table 1 in document https://portal.opengeospatial.org/files/?artifact_id=56357. For some reason it has 4 different integers: Boolean, tinyint, smallint, mediumint, integer, float, double, text, blob, date, datetime GML is having some additional data types. Some of those do not suit well to simple feature model like a few different list types (string list, integer list). I would say that what has been missing from OpenJUMP but what might have had practical importance for me are Long integer (64 bit) because for example ids in OpenStreetMap data are too big to fit in 32 bit nowadays and perhaps Boolean. Date+time are useful too but we have that enhancement to simple shapefile date already. Conclusion: One data type for strings seem to be enough for all the others. I do not understand how big and important is the difference between float, double and real but "double" in OJ which turns inte "Real" in GDAL has always been enough for me. I suppose that the meaning of having variable lengths for integers is to save some storage space if integers are known to be small. -Jukka- > > ..ede ------------------------------------------------------------------------------ Dive into the World of Parallel Programming! The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net _______________________________________________ Jump-pilot-devel mailing list Jump-pilot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel
