Computerized spreadsheets are tremendously popular and useful. Despite their success, computerized spreadsheet systems today have significant and unnecessary restrictions that limit their usefulness. One significant restriction is that the formulas used to specify calculations must be functions. Another unnecessary restriction is that propagation can only occur in one direction. We can lift these restrictions, allowing for many-to-many logical constraints and multidirectional propagation. We call such a spreadsheet a logical spreadsheet. We allow for inconsistency between the constraints of the spreadsheet. To allow for the consequences of the spreadsheet to be shown, we create a new paraconsistent entailment relation and show how it can be computed. We discuss the issues involved in updating a logical spreadsheet, and design a family of domain-independent update operators for updating logical spreadsheets. To allow for domain-dependent behavior, we design a logic called Markov Change Logic that can be used to express update policies for spreadsheets. The design of Markov Change Logic is motivated in part by an analysis of dynamic database constraints, in which we prove that all database constraints can be reduced to Markov dynamic constraints if the schema may be reformulated. We describe the implementation of a logical spreadsheet engine called Webcell which can be used to turn Web pages into logical spreadsheets, and discuss its application to the Stanford Computer Science Master's Program Sheets.program, we can use the insertion and deletion operators to generate a set of insertions and deletions, use the MCL program to generate ... from taking place that are generated by the insertion and deletion operators, we can change Markov Change Logic itself. ... it does not allow one to express conditional statements like awhen p has value a, (use prioritization scheme A); when p has ... Nonetheless, its simplicity makes it very appealing for the circumstances in which it CHAPTER 7.
|Author||:||Michael Adam Kassoff|
|Publisher||:||Stanford University - 2011|