Metadata is data about other data. It summarizes basic information about data which can make working with other particular instances of data easier. Examples of basic document metadata include author, date created, and date modified. Metadata can be attached to a file manually or by automated information processing. Manual creation allows the user to input any relevant information and tends to be more accurate. Automated metadata creation can be more elementary.
Advantages of Metadata include consistency of definitions, clarity of relationships, and the clarity of data lineage. Clarity of relationships, for instance, in relation to file metadata helps resolve ambiguity when determining the associations between entities stored through metadata. Some of the challenges include cost, subjectivity, lack of authentication, and lack of interoperability with respect to semantics, vocabularies, and semantics.