XMP Specification September 2005 33 XMP Storage Model XMP Packet Wrapper 3 Attribute: encoding NOTE: This attribute is deprecated. The optional encoding attribute is identical to the encoding attribute in the XML declaration (see productions [23] and [80] in the XML specification). It was intended to specify the character encoding of the packet, but is redundant with the information from the begin attribute. XMP Data The bytes of the XMP data are placed here. Their encoding must match the encoding implied by the header’s begin attribute. The structure of the data is described in “Serializing XMP” above. The XMP data should not contain an XML declaration. The XML specification requires that the XML declaration be “the first thing in the entity” this is not the case for an embedded XMP Packet. Padding It is recommended that applications place 2 KB to 4 KB of padding within the packet. This allows the XMP to be edited in place, and expanded if necessary, without overwriting existing application data. The padding must be XML-compatible whitespace the recommended practice is to use the ASCII space character (U+0020) in the appropriate encoding, with a newline about every 100 characters. Trailer This required processing instruction indicates the end of the XMP Packet. ?xpacket end='w'? Attribute: end The end attribute is required, and must be the first attribute. NOTE: Other unrecognized attributes can follow, but should be ignored. Attributes must be separated by exactly one ASCII space (U+0020) character. The value of end indicates whether applications that do not understand the containing file format are allowed to update the XMP Packet: ● r means the packet is “read-only” and must not be updated in place. This would be used for example if a file contained an overall checksum that included the embedded XMP. NOTE: The use of r does restrict the behavior of applications that understand the file format and are capable of properly rewriting the file.