The association between data, such as attributes in business objects. The data can be related on a one-to-one, one-to-many, or many-to-many basis. Each participant in the relationship is associated with a simple data type, not a business object. Lookup relationships typically transform non-key attributes whose values are represented with codes, such as marital status or currency code. Use a lookup relationship if the data in the attributes is static, that is, if new values are not often added or existing values removed.