ISO 14721:2012 defines the reference model for an open archival information system (OAIS). OAIS also defines the information model that needs to be adopted. This includes not only the digital material but also any metadata used to describe or manage the material and any other supporting information called Representation Information. For the "modelling" part, the ISO standard recognizes three types of formats for the representation of the contents (SIP - AIP - DIP) and specifies what must be represented: the Content Information, the Preservation Description Information (the origin, the context, the identification and integrity of the published content), Packaging and Content Description. On the other hand, OASIS does not define specific data formats.