Extensible Metadata Platform (XMP) Specification - Adobe Partners
Extensible Metadata Platform (XMP) Specification - Adobe Partners
Extensible Metadata Platform (XMP) Specification - Adobe Partners
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4<br />
<strong>XMP</strong> Schemas<br />
<strong>XMP</strong> Media Management Schema<br />
NOTE: This terminology should be distinguished from HTTP terminology, where resource is<br />
most often used in the sense of “container”, while entity or entity-part is always used to<br />
mean “the current content of all or part of a resource at some point in time.”<br />
An ID should be a GUID/UUID-style ID, which is a large integer that is guaranteed to be<br />
globally unique (in practical terms, the probability of a collision is so remote as to be<br />
effectively impossible). Typically 128- or 144-bit integers are used, encoded as 22 or 24 base-<br />
64 characters.<br />
<strong>XMP</strong> does not require any specific scheme for generating the unique number. There are<br />
various common schemes available for that purpose, such as:<br />
● Using physical information such as a local Ethernet address and a high resolution clock.<br />
●<br />
NOTE: When creating a unique ID, applications must consider tradeoffs between privacy<br />
and the desire to create an audit trail. <strong>Adobe</strong> applications favor privacy and do not<br />
include Ethernet addresses.<br />
Using a variety of locally unique and random data, then computing an MD5 hash value.<br />
This avoids privacy concerns about the use of Ethernet addresses. It also allows for<br />
regeneration of the ID in some cases; for example if the MD5 hash is computed using the<br />
image contents for a resource that is a digital photograph.<br />
46 September 2005 <strong>XMP</strong> <strong>Specification</strong>