Types of metadata

The two basic types of metadata are technical metadata and descriptive metadata.

Technical metadata is useful for software applications that are dealing with digital assets and should not be maintained manually. Experience Manager Assets and other software automatically determine technical metadata and the metadata may change when the asset is modified. The available technical metadata of an asset depends largely on the file type of the asset. Some examples of technical metadata are:

  • Size of a file.
  • Dimensions (height and width) of an image.
  • Bit rate of an audio or video file.
  • Resolution (level of detail) of an image.

Descriptive metadata is metadata concerned with the application domain, for example, the business that an asset is coming from. Descriptive metadata cannot be determined automatically. It is created manually or semi-automatically. For example, a GPS-enabled camera can automatically track the latitude and longitude and add geotag the image.

The cost of manually creating descriptive metadata information is high. So, standards are established to ease the exchange of metadata across software systems and organizations. Experience Manager Assets supports all relevant standards for metadata management.

Encoding standards

There are various ways to embed metadata in files. A selection of encoding standards are supported:

  • XMP: used by Assets to store the extracted metadata within the repository.
  • ID3: for audio and video files.
  • Exif: for image files.
  • Other/Legacy: from Microsoft Word, PowerPoint, Excel, and so on.

XMP

Extensible Metadata Platform (XMP) is an open standard that is used by Experience Manager Assets for all metadata management. The standard offers universal metadata encoding that can be embedded into all file formats. Adobe and other companies support XMP standard as it provides a rich content model. Users of XMP standard and of Experience Manager Assets have a powerful platform to build upon. For more information, see XMP.

ID3

Data stored in these ID3 tags is displayed when you play back a digital audio file on either your computer or a portable MP3 player.

ID3 tags are designed for the MP3 file format. Additional information on formats:

  • ID3 tags work in MP3 and mp3PRO files.
  • WAV has no tags.
  • WMA has proprietary tags that do not allow open-source implementation.
  • Ogg Vorbis uses Xiph Comments embedded in the Ogg container.
  • AAC uses a proprietary tagging format.

Exif

Exchangeable image file format (Exif) is the most popular metadata format used in digital photography. It provides a way of embedding a fixed vocabulary of metadata properties in many file formats, such as JPEG, TIFF, RIFF, and WAV. Exif stores metadata as pairs of a metadata name and a metadata value. These metadata name-value-pairs are also called tags, not to be confused with the tagging in Experience Manager. Modern digital cameras create Exif metadata and modern graphics software support it. Exif format is the lowest common denominator for metadata management especially for images.

A major limitation of Exif is that a few popular image file formats such as BMP, GIF, or PNG do not support it.

Metadata fields defined by Exif are typically technical in nature and are of limited use for descriptive metadata management. For this reason, Experience Manager Assets offers mapping of Exif properties into common metadata schemata and into XMP.

Other metadata

Other metadata that can be embedded from files include Microsoft Word, PowerPoint, Excel, and so on.

Metadata schemata

Metadata schemas are predefined sets of metadata property definitions that can be used in various applications. Properties are always associated with an asset, meaning that the properties are ‘about’ the resource.

You can also design your own metadata schemata if none exists that meet your needs. Do not duplicate existing information. Within an organization, separating schemata makes it easier to share metadata. Experience Manager provides you with a default list of the most popular metadata schemata. The list helps you to jumpstart your metadata strategy and quickly pick the metadata properties that you need.

The supported metadata schemata supported are listed below.

Standard metadata

  • DC - Dublin Core is an important and widely used set of metadata.
  • DICOM - Digital Imaging and Communications in Medicine.
  • Iptc4xmpCore and iptc4xmpExt - International Press Communications Standard contains many subject-specific metadata.
  • RDF - Resource Description Framework - for generic semantic web metadata.
  • XMP - Extensible Metadata Platform.
  • xmpBJ - Basic Job Ticketing.

Application-specific metadata

The application-specific metadata includes technical and descriptive metadata. If you use such metadata, other applications may not be able to use the metadata. For example, a different image-rendering application may not be able to access Adobe Photoshop metadata. You can create a workflow step that changes an application-specific property to a standard property.

  • ACDSee - Metadata managed by the ACDSee program. See www.acdsee.com/.
  • Album - Adobe Photoshop Album.
  • CQ - Used by Experience Manager Assets.
  • DAM - Used by Experience Manager Assets.
  • DEX - Optima SC Description explorer is a collection of tools for metadata and file management for Windows operating systems.
  • CRS - Adobe Photoshop Camera Raw.
  • LR - Adobe Lightroom.
  • MediaPro - iView MediaPro.
  • MicrosoftPhoto and MP - Microsoft Photo.
  • PDF and PDF/X.
  • Photoshop and psAux - Adobe Photoshop.

Digital Rights Management metadata

Photography-specific metadata

  • Exif - Technical information from camera, including GPS position.
  • CRS - Camera Raw schema.
  • iptc4xmpCore and iptc4xmpExt.
  • TIFF - image metadata (not only for TIFF images).

Multimedia-specific metadata

  • xmpDM - Dynamic Media.
  • xmpMM - Media Management.

Metadata-driven workflows

Creating metadata-driven workflows help you automate some processes, which improves efficiency. In a metadata-driven workflow, the workflow management system reads the workflow and as a result performs some pre-defined action. For example, some of the ways you could use metadata-driven workflows:

  • The workflow can check whether an image has a title or not. If it does not, the system notifies to add a title.
  • The workflow can check whether a copyright notice on an asset allows for distribution or not. So, the system sends the asset to one server or the other.
  • A workflow can check for assets without pre-defined, mandatory metadata or assets with invalid metadata.

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