XMP and IPTC: What's the difference?
IPTC - the International Press Telecommunications Council (www.iptc.org) is a consortium of major news agencies across the world. This group set the standard fields of metadata to facilitate sending and receiving image data between parties.
XMP is the new "Extensible Metadata Platform" that was developed by Adobe around 2001. It's based on XML and was designed to allow the exchange of standardized and custom metadata. It's a format that can be used to describe any digital asset or file.
Are IPTC and XMP compatible?
In 2004, the IPTC introduced the IPTC Core schema for XMP, which means that all IPTC metadata can be seamlessly transferred to the more modern and far more flexible XMP format. The current IPTC Core schema has five fields: Title, Subject/Keywords, Creator, Rights/Copyright Notice, Description.
NOTE: IPTC defines the length of the fields (32 characters) while XMP allows more text in these fields. So please keep in mind that when you are exporting from XMP into IPTC the text could be truncated.