Lambda the Ultimate

NEXCEL, a Deductive Spreadsheet, Iliano Cervesato. 2006.

Usability and usefulness have made the spreadsheet one of the most successful computing applications of all times: millions rely on it every day for anything from typing grocery lists to developing multimillion dollar budgets. One thing spreadsheets are not very good at is manipulating symbolic data and helping users make decisions based on them. By tapping into recent research in Logic Programming, Databases and Cognitive Psychology, we propose a deductive extension to the spreadsheet paradigm which addresses precisely this issue. The accompanying tool, which we call NEXCEL, is intended as an automated assistant for the daily reasoning and decision-making needs of computer users, in the same way as a spreadsheet application such as Microsoft Excel assists them every day with calculations simple and complex. Users without formal training in Logic or even Computer Science can interactively define logical rules in the same simple way as they define formulas in Excel. NEXCEL immediately evaluates these rules thereby returning lists of values that satisfy them, again just like with numerical formulas. The deductive component is seamlessly integrated into the traditional spreadsheet so that a user not only still has access to the usual functionalities, but is able to use them as part of the logical inference and, dually, to embed deductive steps in a numerical calculation.

This is a neat paper about using Datalog-style relations to extend spreadsheets with some deductive database features. It seems like Datalog represents a real sweet spot in the design space for logic programming -- I've seen a lot of people put it to effective use.