Logical schema to allow access to a relational database without using knowledge of the database structure

A computer system comprising:

• a memory for storing a logical schema for providing an interface for a user to access data stored in a plurality of relational database tables, each of said relational database tables having at least one field, wherein the logical schema comprises a plurality of logical schema tables, each corresponding to a relational database table and participating in at least one logical relationship, each logical relationship comprising a pair of logical schema tables, a loin field common to both of the logical schema tables in the pair, and a loin operator for joining the pair of logical schema tables based on the join operator, the logical relationship being one of One-to-One, One-to-Zero-or-One, One-to-Zero-or-More, and One-to-One-or-More, the logical schema defining a multilevel hierarchy of the logical schema tables wherein a first table and a second table of a pair of tables in a logical relationship are at an equal hierarchy level if the logical relationship is one of One-to-One and One-to-Zero-or-One and the first table is at a higher hierarchy level than the second table if the logical relationship is one of the One-to-Zero-or-More and One-to-One-or-More;
• and
• a display for displaying fields of the logical schema tables.

A computer-implemented method for providing a hierarchical view of data stored in a plurality of relational database tables comprising the steps of:

• providing a logical schema for at least two logical schema tables, each logical schema table corresponding to a relational database table, wherein the logical schema is defined by pairwise logical relationships between the logical schema tables, each logical schema table participating in at least one logical relationship, wherein a logical relationship is defined by a join operator on a join field common to both logical tables in the pair, and a logical relationship is one of One-to-One, One-to-Zero-or-One, One-to-Zero-or-More, and One-to-One-or-More;
• and
• establishing a multilevel hierarchy among the logical schema tables, wherein a first table and a second table of the pair of tables in each logical relationship are at an equal hierarchy level if the logical relationship is one of One-to-One and One-to-Zero-or-One, and the first table is at a higher hierarchy level than the second table if the logical relationship is one of One-to-Zero-or-More and One-to-One-or-More.