KeyView 24.4
KeyView XML Export SDK C Programming Guide

# 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- `bIsSuperseded` specifies whether this element has been superseded, meaning that this element exists only to preserve backwards compatibility. An element can be superseded to fix issues with the key or value type.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`.

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Version 24.4 | Last updated September 2024

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Product: IDOL KeyView 24.4

Topic Title: Metadata Elements