XMP
From Just Solve the File Format Problem
Extensible Metadata Platform (XMP) is a metadata standard that can be used with a variety of file formats. When stored in a file, it is usually represented in a text format based on XML.
Embedding
The XMP Specification (Part 3) defines how to embed XMP in some popular file formats.
In a TIFF file, tag 700 is used.
In a JPEG file, an APP1 segment with identifier "http://ns.adobe.com/xap/1.0/" is used.
In a PNG file, an iTXt chunk with keyword "XML:com.adobe.xmp" is used.
