Implicit joins in the structural data model

In general, writing a relational query involving many join predicates is cumbersome and prone to errors. One approach to resolving this problem is the implicit join method. This method derives the unspecified join predicates of an incompletely specified query from the semantic dependency-a set of the pairs of semantically dependent attributes-in the database schema. Although the implicit join method has some advantages over the universal relation approach, it frequently derives a complete query differently from what a user would do, and generates redundant subqueries. It is shown that using the structural model removes the problem of redundancy by making the semantic observation of the database schema possible, and provides a complete query that many users would prefer to that of the original implicit join method