RDF, (Resource Description Framework), is a set of engineering specifications for the normalization of the metadatos in XML, we can say that RDF provides a generic tool for the creation, management and search of intelligible data by machines in the Web. It transforms the Web into repositorio of sortable information by machines, the essential advantages is to facilitate the interoperability in the metadatos, provides a semantics for the creation of intelligible metadatos by machines, offers major precision in the recovery of resources that the searches to plaintext. The main target of the RDF concentrates in establishing a mechanism that allows to describe resources that they have like principles to work in multiplatform and the interoperativity of the data. The mechanism used for it must be neutral with respect to the area of application and, at the same time, sufficiently flexible like describing any type of information. Whereas language XML is used for the syntax of the RDF matters for the semantics, because it offers of clear way a series of rules to provide descriptive information.
RDF Integra a great variety of applications, as they can be catalogues of libraries, directories Web, particular collections of music, photos, events, etc. can be used XML like an interchange syntax. Recommendations RDF offer a very powerful structure to support the interchange of knowledge in the Web. RDF has supposed one of the majors advances in the Web. For the understandable bibliographical exchange of information by the computer, format MARC (Legible Cataloguing by Machine), is designed to codify the data of the registry and each one of the elements of the catalogrfica card have assigned a numerical identifier of three numbers. Within each field it counts on indicators that specify their content, codes of subfield that identify a concrete element of the field and delimiters that indicate the location of the field within the registry. .