SQL Databases are a Moving Target

Our position is founded on two assumptions. First, we assume that the SQL data definition language (SQL-DDL) is capable of encoding substantial domain semantics, albeit not in ways syntactically accessible to inference engines. Second, the layered architecture of the Semantic Web, a.k.a. the layer cake, transcends the Semantic Web. In other words, we assume that the hierarchy of increasingly expressive Semantic Web languages embody a generalizable organizational principle. We do not venture to draw parallels to computational hierarchies. Rather, we cast SQL-DDL into a Semantic-Web like layer cake with the intention to make apparent SQL’s ability to embody semantics and to rationalize the approach of mapping relational databases to the Semantic Web. Even though proportionally few applications exploit the full expressive power of SQL-DDL we show that it is important to develop relational database to Semantic Web mappings that anticipate the full expressive power of SQL.