XMP Specification September 2005 15 XMP Data Model Property Values 2 An XMP Schema will also have a preferred namespace prefix. Property names are often written in documentation with the prefix in the manner of XML qualified names, such as dc:creator. Following the rules of XML namespaces, use of this prefix is only a suggestion not a requirement. The actual prefix used when saving XMP might differ, and is local to the xmlns attribute that declares it. Use of standard URI schemes is encouraged when creating namespace URIs. In order to avoid collisions, the URI should contain a component owned by the namespace creator such as an Internet domain name. Do not create namespaces in domains owned by others. NOTE: The example namespaces used here, such as http://ns.example.com/xyz/, are all artificial. They do not exist and should not be used as a model for real namespaces. The term “top level” distinguishes the root properties in an XMP Schema from the named fields of a structure within a property value. By convention an XMP Schema defines its top level properties, the names of structure fields are part of the data type information. Property Values The data types that can represent the values of XMP properties are in three basic categories, described here: simple types, structures, and arrays. Since XMP metadata is stored as XML, values of all types are written as Unicode strings. This section shows conceptual examples of XMP data types. “Serializing XMP” on page 21 shows how these examples are represented in XML. Definitions of all predefined properties and value types can be found in Chapter 4, “XMP Schemas”. Simple Types A simple type has a single literal value. Simple types include familiar ones such as strings, booleans, integers and real numbers, as well as others such as Choice. In this figure, the document XMP_Specification.pdf is shown with 2 simple properties: ● The value of the property dc:format is the MIMEType value "application/pdf". XMP_Specification.pdf dc:format xmp:CreateDate "application/pdf" "2002-08-15T17:10:04-06:00"