The document data store is a database used to manage large numbers of documents
and the structured data that is associated with them. The document contents
are typically stored in compressed form for efficiency. The structured data
consists of document metadata and other information extracted from the documents,
such as links and anchor text (the text associated with a link). A relational
database system can be used to store the documents and metadata. Some applications,
however, use a simpler, more efficient storage system to provide very fast
retrieval times for very large document stores.