Metadata Elements

This section explains how to process metadata elements using the KeyView API.

Standardized Elements

When KeyView understands the meaning of a metadata field in a document, it outputs that data in a standardized element - a KVMetadataElement object where:

  • eKey is the standard key, which indicates the meaning of the element. For a list of standard keys, see Standardized Metadata Elements. The standard key will not be equal to KVMetadataKey_Other.
  • pKey is uniquely determined by eKey. If you are handling the value of a standardized element based on its eKey, you can ignore pKey. pKey is provided so that standardized elements can optionally be handled in the same way as non-standardized elements.

  • pValue is converted to a standard type, and, where appropriate, standard units.

  • bHasStandardAlternative is false.

  • bIsSuperseded specifies whether this element has been superseded, meaning that this element exists only to preserve backwards compatibility. An element can be superseded to fix issues with the key or value type. When this value is true, the same metadata is available through an improved KVMetadataElement in the same KVMetadataList.

Each standardized element is guaranteed to occur at most once in the metadata output. For example, the metadata output will contain zero or one KVMetadataElement objects with eKey equal to KVMetadataKey_Title.

Non-standardized Elements

Non-standard elements represent native metadata fields. Some non-standard elements might have been used to create a standardized element, and therefore have a standardized alternative. User-created metadata fields, and fields that are unique to one file format, are usually available only as non-standard elements. For a non-standard metadata element:

  • eKey is set to KVMetadataKey_Other.
  • pKey contains a string representation of a field's key. If a field key exists in the document, pKey is set to that string. Otherwise, KeyView generates a value.
  • pValue contains the field's value, stored in an appropriate data type.
  • bHasStandardAlternative specifies whether a non-standardized element has a standardized counterpart. When this member is true, this element contains metadata that also exists in a standardized KVMetadataElement in the same KVMetadataList. The standardized element might present the metadata with different units.
  • bIsSuperseded specifies whether this element has been superseded, meaning that this element exists only to preserve backwards compatibility. An element can be superseded to fix issues with the key or value type. When this value is true, the same metadata is available through an improved KVMetadataElement in the same KVMetadataList.