Metadata Elements
This section explains how to process metadata elements.
Standardized Elements
When File Content Extraction understands the meaning of a metadata field in a document, it outputs that data in a standardized element - a MetadataElement object where:
-
the
standard_keyattribute contains the standard key, which indicates the meaning of the element. For a list of standard keys, refer to theMetadataKeyenumeration or see Standardized Metadata Elements. The standard key will not be equal toMetadataKey.Other. -
the
keyattribute contains a string that is uniquely determined by the standard key. If you are handling the value of a standardized element based on its standard key, you can ignore this value. It is provided so that standardized elements can optionally be handled in the same way as non-standardized elements. - the
has_standard_alternativeattribute isfalse. - the
is_supersededattribute specifies whether this element has been superseded, meaning that this element exists only to preserve backwards compatibility. An element can be superseded to fix issues with the key or value type.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 attribute istrue, the same metadata is available through an improvedMetadataElementreturned by the sameMetadataiterator.
Each standardized element is guaranteed to occur at most once in the metadata output. For example, a Metadata object will contain zero or one MetadataElement objects with the standard key MetadataKey.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:
- the
standard_keyattribute is equal toMetadataKey.Other. - the
keyattribute contains a string representation of a field's key. If a field key exists in the document, that value is returned. Otherwise, File Content Extraction generates a value. - the
has_standard_alternativeattribute specifies whether the element has a standardized alternative. When this attribute istrue, this element contains metadata that also exists in a standardizedMetadataElementreturned by the sameMetadataiterator. The standardized element might present the metadata with different units. - the
is_supersededattribute specifies whether this element has been superseded, meaning that this element exists only to preserve backwards compatibility.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 attribute istrue, the same metadata is available through an improvedMetadataElementreturned by the sameMetadataiterator.