The term was introduced intuitively, without a formal definition. Because of that, today there are various definitions. The most common one is the literal translation: Metadata is “data about data”, of any sort in any media. Metadata is text, voice, or image that describes what the audience wants or needs to see or experience. The audience could be a person, group, or software program. Metadata would document data about data elements or attributes, data about records or data structures and data about data. Metadata may include descriptive information about the context, quality and condition, or characteristics of the data.
An example of metadata occurs within file systems. Associated with every file on the storage medium is metadata that records the date the file was created, the date it was last modified and the date the file (or indeed the metadata itself) was last accessed.
Metadata is used to facilitate the understanding, usage, and management of data by human and computers. The metadata required to effectively work with data varies with the type of data, their context of use, and their purpose.
Often data providers will provide users access to a variety of metadata fields, which can be used individually or in combinations, and applied by different users to achieve different goals. These users can be human, or other computing systems.
Metadata has many different applications and these are some of them:
- Metadata is becoming an increasingly important part of electronic discovery. Application and file system metadata derived from electronic documents and files can be important evidence.
- Metadata has become important on the Word Wide Web because of the need to find useful information from the mass of information available.
- Metadata is used to speed up and enrich searching for resources. In general, search queries using metadata can save users from performing more complex filter operations manually.
- Metadata may also be associated to files manually. This is often the case with documents which are scanned into a document storage repository such as FileNet or Documentum.
- Metadata provide additional information to users of the data it describes. This information may be descriptive or algorithmic.
- Metadata helps to bridge the semantic gap. By telling a computer how data items are related and how these relations can be evaluated automatically, it becomes possible to process even more complex filter and search operations.
Metadata can be classified by:
- Content. Metadata can either describe the resource itself or the content of the resource .
- Mutability. With respect to the whole resource, metadata can be either immutable or mutable
- Logical function. There are three layers of logical function:
- Subsymbolic layer: contains the raw data itself
- Symbolic layer : metadata describing the raw data
- Logical layer: containing metadata that allows logical reasoning using the symbolic layer
Finally, we can find five types of metadata:
- descriptive metadata.
- administrative metadata.
- structural metadata.
- technical metadata.
- use metadata
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