Source of Metadata

Metadata can be extracted from various sources that are available from system. We distinguish four main categories [16] of metadata sources

• Document content analysis: One obvious source for metadata about an object is the object itself. An objectbased indexer generates metadata using the object independent from any specific usage. Typical content analyzers are keyword extractors, language analyzers for text documents or pattern recognizers for images.
• Document context analysis: When an object is used in a specific context and data about that context are available, we can rely on the context to obtain information about the object itself. One single learning object typically can be deployed in several contexts which provide us with metadata about it.
• Document usage: Real use of objects can provide us with more flexible and lively metadata than the sometimes more ''theoretical'' values provided by other metadata sources, or even by human indexers. Systems that track and log the real use of documents by learners are therefore a valuable source. These logs for example store the time spent reading a document or solving exercises. This metadata source category could be considered as a ''usage context'', and as such as a special case of document context analysis.
• Composite documents structure: In some cases, learning objects are parts of a whole but stored separately. In such a case, the metadata available for the whole is an interesting source for metadata about a component. Not only is the enclosing object a source, also the sibling components can provide relevant metadata. For example, one slide in a slide show often gives relevant context about the content of the next slide.This could be considered as a special case of document context, namely ''aggregation related context''.