PrediCalc: A Logical Spreadsheet Management System

Michael Kassoff

Lee-Ming Zen

Ankit Garg

Michael Genesereth

August 30, 2005

Stanford Logic Group VLDB 2005 Demo

Electronic Spreadsheets

• Huge success

• Used by everyone from multinational conglomerates to individuals

• Limitations– Functional definitions– Unidirectional update

From Functions to Constraints

Generalizing formulae to many-to-many constraints allows us to use spreadsheets for a wide variety of applications

• Correct-on-capture data entry (smart forms)– “Start times must be before end times”– “The number of lap infants traveling must not be greater

than the number of adults”

• Enterprise Management policies– “Only senior managers can reserve the third floor

conference room”

• Design / Configuration– “Students must take at least 2 math courses to graduate”

Logical Spreadsheets

We choose to represent many-to-many relationships using logical formulae

start-time(S) and end-time(E) before(S,E) “The start time must be before the end time”

event-owner(O) and senior-manager(O) event-room(room301)

“Only senior managers can reserve the third floor conference room”

The focus is on symbolic data rather than numeric data

Features of PrediCalc

• Distinguishes between user-specified cells and computed cells– Computed cells contain logical

consequences of user-specified cells– Allows for simple retraction of value

assignments

• Propagation can occur in any direction

• Constraints are not independent: p(X) q(X)

q(X) r(X)

User specified

System generated

b

p q

b

a

p q

a

p(X) q(X)

p(X) r(X)

Inconsistency Tolerance

• Uses a novel technique to handle inconsistency of values with constraints

• Gives users feedback about violated constraints

(I can’t explain this in 5 minutes… see the demo!)

Thanks!