Meta Data: Meta data is “data about data”. An item of metadata describes the specific characteristics about an individual data item. In databases, metadata describes the structural components of tables and their elements. For example, metadata about an element could include data types, name of data, size and many more characteristics about that element. It would also give information about the tables the database is storing, information, such as length of fields, number of columns, where the tables are located and other pertinent information. One of the main uses for met data is to provide a link between the information creator and the information users. Meta data allows the users to speed up the search for individual data. This is done by being able to set parameter for searches, allowing the filtering of unwanted information. Meta data can be stored either internally, in the same file as the data or externally, in a separate area. Both have advantages and disadvantages. I f the data is stored internally, the meta data is together with the data making more easily accessible to view or change. However, this method creates high redundancy. If metadata is stored externally, the searches can become more efficient. There is no redundancy but getting to this metadata may be a little more technical. There are certain formats that most be used, such as Uniform Resource Identifier(URI) to get to the meta data, if this format is not used the meta data becomes in accessible. All the metadata is stored in a data dictionary or a system catalog. All programs that access data in the database work through a DBMS. The DBMS use the data dictionary to look up the required components and relationships. Any changes made to the database structure are automatically recorded in the data dictionary. This makes the data dictionary manager’s job a lot easier, because any modification of programs that are affected by changed structure is not necessary.

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