1. A method of providing a unified view of data existing in multi layered hierarchical structure in an enterprise application by modeling the data at multiple levels of abstraction and capturing the relationships existing between the modeled data, the method comprising the processor implemented steps of: defining a global schema using a conceptual modeling framework to provide an aggregated view of the data; defining a source schema at multiple levels using a conceptual model for at least one level and a relational model or a conceptual model for subsequent levels; capturing a relationship between data existing at multiple levels within an hierarchical structure; establishing mappings and mapping rules to codify captured relationships existing between the defined global schema and set of source schema; initializing a query on the global schema and rewriting into an equivalent source schema such that the query in the source schema is maximally contained in the global schema; capturing relationship derivation dependencies between the data contained in the defined global schema and source schema by constructing a directed acyclic graph from the established mapping rules and conceptual models; processing the directed acyclic graph to construct a mapping system, the mapping system having alternate global-as-view (GAV) and local-as-view (LAV) mapping layers; translating the queries down multiple levels of the conceptual model into physical model queries by applying the obtained alternate GAV and LAV mapping layers; and executing the translated physical model query either directly or indirectly by translating the query into a data flow graph that can optionally be exported into third party Extract, Transform, Load (ETL) tools.