A format in computer term is a convention on a representation data on a digital media. It can be:
- Specified :there is a description of the convention used to represent the data and it is sufficiently described to develop a complete implementation
- Open : Convention is public (otherwise the format is said to be closed). It is therefore of an access or of an implementation unrestricted.
- Standardized : the agreement is adopted by standardization agencies (ISO, W3C). Example: PDF / A.
- Proprietary : if the format exploitation is part of private law, it then depends on the existence of the owner. It can be published. Example: PDF or Word.
These four criteria can define the level of sustainability of a format.