1. A computer-implemented method for retaining data in a storage layer according to a high-level policy comprising: describing the high-level policy as a table on a regulation layer, the table including a high-level object and attributes of the high-level object, the attributes including a retention time indicating how long the high-level object needs to be retained and a start event from which the retention time is measured; performing a first data mapping of the high-level object in the regulation layer to a data type in a business model layer, said first data mapping performed by substituting the high-level objects in the table in the regulation layer with corresponding data types in the business model layer, wherein for each high-level object defining a row of the table, the high-level object is mapped to one or more data types in a set of {B1,. .. , Bn} on the business model layer wherein attributes of the high-level object row in the table are replaced with attributes of each data type of the set {B1,. .. , Bn} on the business model layer, wherein: one-to-one mapping substitution indicates one high-level object having exactly one corresponding data type {Bi} in the business model layer, one-to-several mapping substitution indicates one high-level object having several corresponding data types {B1,. .. , Bn} in the business model layer, one-to-subtype mapping substitution indicates one high-level object corresponds to a subtype {Si} of a data type {Bi} in the business model layer, and one-to-union of several subtypes mapping substitution indicates that the high-level object corresponds to a union of several subtypes {S1,. .. , Sn} of the set {B1,. .. , Bn} in the business model layer; and mapping the start event in the regulation layer to a start-event-action in the business model layer by substituting the corresponding start-event-action in the business model layer for the start event in the regulation layer, the start-event-action being one of: an action, a set of several actions, subsets of actions, or a pair of a precondition of the start event and a postcondition of the start event in the business model layer; performing a second data mapping of the data type of the business model layer to a data item in the storage layer, said second data mapping performed by: mapping the start-event-action in the business model layer to actual executable steps in the storage layer when the start-event-action is one of the action, the set of several actions or the subsets of actions; transforming, when the start event is mapped to the pair of a precondition of the start event and a postcondition of the start event in the business model layer, the pair of a precondition of the start event and a postcondition of the start event in the business model layer to a similar pair of a precondition of the start event and a postcondition of the start event in the storage layer; deriving a low-level policy from the high-level policy by substituting the high-level object with the data item and substituting the start event with the actual executable steps or the similar pair of a precondition of the start event and a postcondition of the start event; and retaining the data item in the storage level in accordance with the start event, wherein a processor coupled to a memory device perform: the describing, the mapping the high-level objects, the mapping the start event, the mapping the one corresponding data type, the mapping the action, the transforming, and the deriving.