1. A method for accessing data comprising: identifying a first schema information library, wherein the first schema information library includes first schema information which contains a data access path to data in a hierarchical database, external schema information, and conceptual schema information; converting using a computer memory, the first schema information to second schema information, wherein the second schema information is tree-structured data; storing the second schema information in a second schema information library; expanding the second schema information to define a tree-structured database; storing the tree-structured data information in a tree-structured database storage section; receiving a first access request from an application program for data contained in the hierarchical database; identifying, in response to the step of receiving, a single node of the tree-structured data information, wherein the single node contains information required to access the data in the hierarchical database; generating a second access request from the information retrieved from the single node; and using the second access request to access the data in the hierarchical database.