next up previous contents
Next: Property Theory (PT) Up: Squirrel Documentation Previous: Compiling the grammar

Stages of Translation


Squirrel uses information obtained during a successful parse of a question to produce a formal representation of its meaning expressed in Property Theory. This expression is then translated through the following representations and optimisations to produce the final SQL query.

  1. Property Theory (PT).
  2. First order logic (FOL).
  3. Untyped Relational Calculus (URC).
  4. Domain Relational Calculus (DRC).
  5. First Optimisation (OP1).
  6. Tuple Relational Calculus (TRC).
  7. Second Optimisation (OP2).
  8. Third Optimisation (OP3).
  9. SQL.

The query becomes database specific when it is mapped from the First Order Logic to the Untyped Relational Calculus. It is at this point that information in the the Extended Data Model (EDM) is used to relate semantic constructions derived from the query with the kinds of relations available in the database.

Chris Fox, September 1995