Book contents
- Frontmatter
- Contents
- Acknowledgments
- 1 Introduction
- 2 Classes of update semantics
- 3 Model-based semantics for updates
- 4 Update algorithms for model-based semantics
- 5 Updates with variables
- 6 Lazy evaluation of updates
- 7 Integrity constraints
- 8 Adding knowledge to relational theories
- 9 Implementation
- Bibliography
- Index of definitions
8 - Adding knowledge to relational theories
Published online by Cambridge University Press: 22 March 2010
- Frontmatter
- Contents
- Acknowledgments
- 1 Introduction
- 2 Classes of update semantics
- 3 Model-based semantics for updates
- 4 Update algorithms for model-based semantics
- 5 Updates with variables
- 6 Lazy evaluation of updates
- 7 Integrity constraints
- 8 Adding knowledge to relational theories
- 9 Implementation
- Bibliography
- Index of definitions
Summary
“ … You believers make so many and such large and such unwarrantable assumptions.”
“My dear, we must make assumptions, or how get through life at all?”
“Very true. How indeed? One must make a million unwarrantable assumptions, such as that the sun will rise tomorrow, and that the attraction of the earth for our feet will for a time persist, and that if we do certain things to our bodies they will cease to function, and that if we get into a train it will probably carry us along, and so forth. One must assume these things just enough to take action on them, or, as you say, we couldn't get through life at all. But those are hypothetical, pragmatical assumptions, for the purposes of action: there is no call actually to believe them, intellectually. And still less call to increase their number, and carry assumption into spheres where it doesn't help us to action at all. For my part, I assume practically a great deal, intellectually nothing.”
—Rose Macaulay, Told by an IdiotRelational theories contain little knowledge, that is, data about data. The exact line between knowledge and data is hard to pinpoint; for our purposes, the distinguishing characteristic of knowledge will be our reluctance to change it in response to new information in the form of an update. Under this categorization, the integrity constraints discussed in Chapter 7 are a form of knowledge.
- Type
- Chapter
- Information
- Updating Logical Databases , pp. 159 - 177Publisher: Cambridge University PressPrint publication year: 1990