XMP (Extensible Metadata Platform) is the metadata standard used by AEM Assets for all metadata management. XMP provides a standard format for the creation, processing, and interchange of metadata for a wide variety of applications.
Aside from offering universal metadata encoding that can be embedded into all file formats, XMP provides a rich content model and is supported by Adobe and other companies, so that users of XMP in combination with AEM Assets have a powerful platform to build upon.
XMP overview and ecosystem
AEM Assets natively supports the XMP metadata standard. XMP is a standard for processing and storing standardized and proprietary metadata in digital assets. XMP is designed to be the common standard that allows multiple applications to work effectively with metadata.
Production professionals, for example, use the built-in XMP support within Adobe's applications to pass information across multiple file formats. The AEM Assets repository extracts the XMP metadata and uses it to manage the content lifecycle and offers the ability to create automation workflows.
XMP standardizes how metadata is defined, created, and processed by providing a data model, a storage model, and schemas. All of these concepts are covered in this section.
All legacy metadata from EXIF, ID3, or Microsoft Office is automatically translated to XMP, which can be extended to support customer-specific metadata schema, such as product catalogs.
Metadata in XMP consists of a set of properties. These properties are always associated with a specific entity referred to as a resource; that is, the properties are “about” the resource. In the case of XMP, the resource is always the asset.
XMP defines a metadata model that can be used with any defined set of metadata items. XMP also defines particular schemas for basic properties 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 assembly into a final image. XMP allows each software program or device along the way to add its own information to a digital resource, which can then be retained in the final digital file.
XMP is most commonly serialized and stored using a subset of the W3C Resource Description Framework (RDF), which is in turn expressed in XML .
Advantages of XMP
XMP has the following advantages over other encoding standards and schemata:
- XMP-based metadata is very powerful and fine-grained.
- XMP lets you have multiple values for one property.
- XMP has standardized encoding, which lets you easily exchange metadata.
- XMP is extensible. You can add additional information into your assets.
The XMP standard is designed to be extensible, allowing you to add custom types of metadata into the XMP data. EXIF, on the other hand, does not - it has a fixed list of properties that cannot be extended.
XMP generally does not allow binary data types to be embedded. To carry binary data in XMP, for example, thumbnail images, they must be encoded in an XML-friendly format such as Base64 .
XMP core concepts
Namespaces and schemata
An XMP schema is a set of property names in a common XML namespace that includes the data type and descriptive information. An XMP schema is identified by its XML namespace URI. Using namespaces prevents conflicts between properties in different schemas that have the same name but a different meaning.
For example, the Creator property in two independently designed schemas might mean the person who created the asset or it could mean the application that created the asset (for example, Adobe Photoshop).
XMP properties and values
XMP may include properties from one or more of the schemas. For example, a typical subset used by many Adobe applications might include the following:
- Dublin core schema: dc:title , dc:creator , dc:subject , dc:format , dc:rights
- XMP basic schema: xmp:CreateDate , xmp:CreatorTool , xmp:ModifyDate , xmp:metadataDate
- XMP rights management schema: xmpRights:WebStatement , xmpRights:Marked
- XMP media management schema: xmpMM:DocumentID
XMP offers you the ability to add an xml:lang property to text properties to specify the language of the text.
XMP writeback to renditions
This XMP write-back feature in Adobe Experience Manager (AEM) Assets replicates asset metadata changes to the renditions of the asset.
When you change the metadata for an asset from within AEM Assets or while uploading the asset, changes are initially stored within the asset node in CRXDE.
The XMP write-back feature propagates the metadata changes to all or specific renditions of the asset.
Consider a scenario where you modify the Title property of the asset titled Classic Leather to Nylon .
In this case, the AEM Assets saves the changes to the Title property in the dc:title parameter for the asset metadata stored in the asset hierarchy.
However, AEM Assets does not automatically propagate any metadata changes to the renditions of an asset.
The XMP write-back feature lets you propagate the metadata changes to all or specific renditions of the asset. However, the changes are not stored under the metadata node in the asset hierarchy. Instead, this feature embeds the changes in the binary files for the renditions.
Enable XMP write-back
To enable the metadata changes to be propagated to the renditions of the asset when uploading it, modify the Adobe CQ DAM Rendition Maker configuration in Configuration Manager.
- To open Configuration Manager, access https://[aem_server]:[port]/system/console/configMgr .
- Open the Adobe CQ DAM Rendition Maker configuration.
- Select the Propagate XMP option, and then save the changes.
Enable XMP write-back for specific renditions
To let the XMP write-back feature propagate metadata changes to select renditions, specify these renditions to the XMP Writeback Process workflow step of DAM Metadata WriteBack workflow. By default, this step is configured with the original rendition.
For the XMP write-back feature to propagate metadata to the rendition thumbnails 140.100.png and 319.319.png, perform these steps.
- Tap/click the AEM logo, and then navigate to Tools > Workflow > Models .
- From the Models page, open the DAM Metadata Writeback workflow model.
- In the DAM Metadata Writeback properties page, open the XMP Writeback Process step.
- In the Step Properties dialog box, tap/click the Process tab.
- In the Arguments box, add rendition:cq5dam.thumbnail.140.100.png,rendition:cq5dam.thumbnail.319.319.png , and then tap/click OK .
- Save the changes.
- To regenerate the Pyramid TIFF (PTIFF) renditions for Dynamic Media images with the new attributes, add the Dynamic Media Process Image Assets step to the DAM Metadata write-back workflow. PTIFF renditions are only created and stored locally in a Dynamic Media Hybrid implementation.
- Save the workflow.
The metadata changes are propagated to the renditions renditions thumbnail.140.100.png and thumbnail.319.319.png of the asset, and not the others.