The Extensible Metadata Platform (XMP) is an ISO standard, originally created by Adobe Systems Inc., for the creation, processing and interchange of standardized and custom metadata for digital documents and data sets. XMP standardizes a data model, a serialization format and core properties for the definition and processing of extensible metadata. It also provides guidelines for embedding XMP information into popular image, video and document file formats, such as JPEG and PDF, without breaking their readability by applications that do not support XMP. Therefore, the non-XMP metadata have to be reconciled with the XMP properties. Although metadata can alternatively be stored in a sidecar file, embedding metadata avoids problems that occur when metadata is stored separately. The XMP data model, serialization format and core properties is published by the International Organization for Standardization as ISO 16684-1:2012 standard. Data model The defined XMP data model can be used to store any set of metadata properties. These can be simple name/value pairs, structured values or lists of values. The data can be nested as well. The XMP standard also defines particular namespaces for defined sets of core properties (e.g. a namespace for the Dublin Core Metadata Element Set). Custom namespaces can be used to extend the data model. An instance of the XMP data model is called an XMP packet. Adding properties to a packet does not affect existing properties. Software to add or modify properties in an XMP packet should leave properties that are unknown to it untouched. For example, it is useful for recording the history of a resource as it passes through multiple processing steps, from being photographed, scanned, or authored as text, through photo editing steps (such as cropping or color adjustment), to assemble into a final document. XMP allows each software program or device along the workflow to add its own information to a digital resource, which carries its metadata along. The prerequisite is that all involved editors either actively support XMP, or at least do not delete it from the resource. Serialization The abstract XMP data model needs a concrete representation when it is stored or embedded into a file. As serialization format, a subset of the W3C RDF/XML syntax is most commonly used. It is a syntax to express a Resource Description Framework graph in XML. There are various equivalent ways to serialize the same XMP packet in RDF/XML. The most common metadata tags recorded