External representations

External representations consist of

1. the represented world - the content of a representation (e.g., content of a weather map would be temperatures around the country)
2. the representing world - the format of the representation (e.g., temperatures can be represented by different colors in pictorial form, or by a table)
3. what aspects of the represented world are being represented (e.g., weather map may have states delineated, but not cities)
4. what aspects of the representing world are doing the modelling (e.g. colors map to temperatures)
5. the correspondence between the two worlds (how the content is mapped to the format)

(Palmer, 1977).