All mark-up languages are derived from SGML (Standard Generalized Mark-up Language), which was used in the 1980s in professional environments for technical and scientific publishing. Based on the same “grammar”, the different “formats” are linked to record profiles called Document Type Descriptions (DTD).
XML (Extensible Markup Language) is widely used across many different communities and enables more functionality than traditional MARC formats. Because of its flexibility and extensibility, it supports the expression of different data models. XML is accepted as an industry standard and therefore facilitates interoperability across sectors and is generally easier to process than alternative options. XML is also more powerful for the presentation of hierarchical or analytical information and allows good link management between bibliographic (and authority) records and digital resources.
XML formats are used in the library and archives world, as well as in the publishing and book trade industry.