We usually hear Exif, IPTC and XMP, but when we mean standards related to metadata, it turns out to be more complex. There are Exif, DCF, IPTC-IIM, XMP (a.k.a IPTC Core), and FlashPix. Some standards are not just about metadata, but also among others how to save image files on digital camera.
Here are some standards that I found out so far:
Exif 1 (standardized by JEIDA)
Exif 2 (standardized by JEITA in 1997) *JEIDA changed name to JEITA
Exif 2.1 (standardized by JEITA in 1998)
DCF JEITA in 1999) *This is Exif 2.1+CIFF
Exif 2.2 (standardized by JEITA in 2002)
Exif 2.3 (standardized by JEITA+CIPA in 2010)
FlashPix
IPTC-IIM (standardized by IPTC in 1994) *descriptive metadata only, for JPEG only, largely superseded by XMP
XMP any file 2001 (standardized by Adobe in 2001) *a.k.a. IPTC Core
Links to standards:
IPTC (Information Interchange Model (IIM))
http://en.wikipedia.org/wiki/IPTC_Information_Interchange_Model
XMP
http://en.wikipedia.org/wiki/Extensible_Metadata_Platform
Exif
http://en.wikipedia.org/wiki/Exchangeable_image_file_format
Design rule for Camera File system
http://en.wikipedia.org/wiki/Design_rule_for_Camera_File_system
References:
http://en.wikipedia.org/wiki/Exchangeable_image_file_format#FlashPix_extensions
http://gcoupe.wordpress.com/2011/12/10/picasa-versus-windows-live-photo-gallery/
http://www.controlledvocabulary.com/blog/top-metadata-myths.html
