Generation of Metadata

In the case of structured databases, the norm is to use schema descriptions and associated information (such as database statistics) as metadata. In the case of unstructured textual data and information retrieval, metadata is generally limited to indexes and textual descriptions of data. Metadata in such cases provides a suitable basis for building the higher forms of information
Metadata is commonly generated via three methods [12] :

• Analyzing raw data In many cases, media objects are analyzed and metadata is generated according to the focus of analysis. This is also known as explicit metadata generation.
• Semi-automatic augmentation Semi automatic augmentation of media results in addition meta-information, which cannot be derived from the raw material as such. Examples are the diagnostic findings of a doctor related to computer tomography image, which are based on doctor's experience and state of art in medicine.
• Processing with implicit metadata generation Metadata can be generated implicitly when creating raw media data. For example, a digital camera can implicitly deliver time and date for picture and video taken. Similarly, an SGML editor generate metadata according to document type definition when document is edited.

Generating the metadata can easily be a tedious task although using automatic tools may help. The task is more daunting when attempting to generate a huge volume of metadata without knowing the data, its usage, its background knowledge, and its accuracy, etc. Before generating the metadata, it is necessary to review all the relevant documentation about the data.