Possible minor bug in XMP-rdf:About tag

[StarGeek]

I've noticed that the XMP-rdf group seems to work a bit differently than other xmp groups.  I have some files with the XMP-rdf:About tag set.  If I try to clear out that tag group using -XMP-rdf:all=, the file is unchanged.  It will only get removed if I clear the XMP-rdf:About tag directly (-XMP-rdf:About=).  Additionally, even after I've cleared that tag, if I clear it again, ExifTool will say the file has been updated, even though there isn't any change to be made.  This is different than my experiences with other tags.

Code Select Expand


C:\>exiftool -ver
9.67

C:\>exiftool -about=Test x:\!temp\Test.jpg
    1 image files updated

C:\>exiftool -g1 -XMP-rdf:all x:\!temp\Test.jpg
---- XMP-rdf ----
About                           : Test

C:\>exiftool -XMP-rdf:all= x:\!temp\Test.jpg
    0 image files updated
    1 image files unchanged

C:\>exiftool -g1 -XMP-rdf:all x:\!temp\Test.jpg
---- XMP-rdf ----
About                           : Test

C:\>exiftool -XMP-rdf:about= x:\!temp\Test.jpg
    1 image files updated

C:\>exiftool -g1 -XMP-rdf:all x:\!temp\Test.jpg

C:\>exiftool -XMP-rdf:about= x:\!temp\Test.jpg
    1 image files updated


[Phil Harvey]

I've noticed that the XMP-rdf group seems to work a bit differently than other xmp groups.  I have some files with the XMP-rdf:About tag set.  If I try to clear out that tag group using -XMP-rdf:all=, the file is unchanged.

Yes.  This tag is considered "unsafe" to change, so it isn't affected when writing with wildcards.

Additionally, even after I've cleared that tag, if I clear it again, ExifTool will say the file has been updated, even though there isn't any change to be made.

Yes.  This is consistent.  If you write the same value for any tag, exiftool will always say the file was updated.  It doesn't check to see if the existing value was the same or not.

This is different than my experiences with other tags.

The difference is that you are not allowed to delete rdf:about, so instead ExifTool writes an empty string.  And writing the same thing a second time should always give a "file updated" message, even if it was an empty string.

- Phil