XMP Specification September 2005 45 XMP Schemas XMP Media Management Schema 4 new InstanceID stuff Document and Instance IDs There can often be ambiguity when referring to computer files. The contents of a file can change over time. Depending on the situation, it might be desirable to refer to either: ● a specific state of the file as it exists at a point in time, or ● the file in general, as a persistent container whose content can change. Some characteristics of a file (such as the application that created it) would normally be expected to be persistent over its life. Other characteristics (such as word count) would be expected to change as the content of the file changes. Some characteristics (such as copyright information or authors’ names) might or might not change. In the same way, XMP properties that represent such characteristics of a file are inherently ambiguous as to whether they refer to the current content of a file or to the file in general. XMP itself provides no mechanisms for distinguishing these. Schemas are encouraged, but not required, to define properties in a way that makes this clear. This document uses the term resource to refer to the “thing the metadata is about” in a general sense.Depending on the context, properties may refer to either the specific or persistent aspects described above. In order to refer unambiguously to a specific state of the file, we use the term instance. xmpMM:Versions seq Version Internal The version history associated with this resource. Entry [1] is the oldest known version for this document, entry [last()] is the most recent version. Typically, a media management system would fill in the version information in the metadata on check-in. It is not guaranteed that a complete history of versions from the first to this one will be present in the xmpMM:Versions property. Interior version information can be compressed or eliminated and the version history can be truncated at some point. xmpMM:LastURL (deprecated) URL Internal Deprecated for privacy protection. xmpMM:RenditionOf (deprecated) ResourceRef Internal Deprecated in favor of xmpMM:DerivedFrom. A reference to the document of which this is a rendition. xmpMM:SaveID (deprecated) Integer Internal Deprecated. Previously used only to support the xmpMM:LastURL property. Property Value Type Category Description