Disclosed is a method of constructing at least one data structure from at least one data source. A representation is constructed of the data source and at least one previous view of the data source. From the representations, at least one compulsory entity (eg. "branch") is then identified. This may generally be performed by a user selection. The method then constructs the data structure comprising the compulsory entity and one or more context entities, where the context entities are obtained from the representation and context data obtained from the previous view. Typically the data source is hierarchical and the data structure is hierarchical.