Metadata has been used in IT for many years. Especially, with the ubiquity of WWW , the increasing need for access to different distributed information and the increased use of various sources all demand common representation of metadata.
Metadata is sticked to data and interpret data. Using the attached metadata, the data in metadata processing systems is deciphered. For example, for WWW and systems engineering, metadata is essential for e-business from advertising through directory information items through oringinal enquiry to contract, purchase, delivery and subsequent guarantee or maintenance.
Role of Metadata
Metadata is data about data. Metadata can describe a data source, a particular collection of data, including a file, a database, a table in a relational database, a class in an object-oriented database, an instance of data like tuple in a relational database table and object instance in a class within an object-oriented database, or data associated with the values of an attribute within a domain like the particular value of an attribute in one instance; metadata can describe data models, processes, including an overall processing system environment, a processing system, a process, a component of a process; It can describe a software, a program, or a specification; It can describe an event system, an individual event, a constraint system and an individual constraint; it can describe people and their roles in an IT system; it can describe an organisation, a department, individuals or individuals in a certain role. Metadata can be divided into five types: descriptive, administrative, structural, technical, and use metadata.
Different type of metadata own different standardisation to aid in data exchange, such as the standard of engineering, healthcare, or libraries. Exchange metadata for internet resources – the Dublin Core - has been proposed and used, and a general metadata model, RDF (Resource Description Framework) has been proposed with the implementation language XML.
Importance of metadata
Due to complexity of society, the increasing number of electronical information sources and the increasing number of users, metadata has increasingly become important. It is essential to be used in effective queries, explaining answers, coodinating between information sources. Metadata becomes the glue that holds together the large amount of information and e-Businesss on the internet. Metadata is essential for WWW to be used effectively, for finding relevant information and for holding together data and information from different sources. Metadata is necessay for simplifying queries so that they select those information that the user wants. Metadata is essential for understanding the structural information, its quality and its relevance. Metadata is essential in interprating answers from some complex IS. The following contents introduce the detailed impotance of metadata.
- Metadata can act as an accelerator and improver to searching for resources. For example, through web browser to search and download a certain free software, we can quickly find it by using the relative descriptive metadata.
- Metadata can also be used to find files manually. For Example, when searching historical file administered and stored in a metadate repository, using metadata queries like " type=history", we can quickly find it.
- Metadata can reduce semantic gap and increase linked word phrases to data. For example, if a search engine understands that "VAn Gogh" was a "Dutch painter", it can answer a search query on "Dutch painters" with a link to a web page about Vincent Van Gogh, although the exact words "Dutch painters" never occur on that page.
- Metadata is an important structural data for the application of DBMS. For example, when developing a DBMS, establishing central database is the first step. Thus, we need to define entities, attributes, relationship between them using metadata. In the following illustration, using metadata to describe the type of each field. The field name in each table is known as metadata.
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5. Technical metadata has improved search engine in World Wide Web. In order to obtain useful information from the mass of information available, it is necessary to use metadata to add value for ensuring consistency and variety.
6. Data warehousing is managed by the application of metadata to conveniently organize and retrieve a great deal of business or organicational information and data.
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