| book details |

Database Repairing and Consistent Query Answering

By (author) Leopoldo Bertossi

| on special |

normal price: R 1,602.95

Price: R 1,522.95

| add to trolley |

| book description |

Integrity constraints are semantic conditions that a database should satisfy in order to be an appropriate model of external reality. In practice, and for many reasons, a database may not satisfy those integrity constraints, and for that reason it is said to be inconsistent. However, and most likely, a large portion of the database is still semantically correct, in a sense that has to be made precise. After having provided a formal characterization of consistent data in an inconsistent database, the natural problem emerges of extracting that semantically correct data, as query answers. The consistent data in an inconsistent database is usually characterized as the data that persists across all the database instances that are consistent and minimally differ from the inconsistent instance. Those are the so-called repairs of the database. In particular, the consistent answers to a query posed to the inconsistent database are those answers that can be simultaneously obtained from all the database repairs. As expected, the notion of repair requires an adequate notion of distance that allows for the comparison of databases with respect to how much they differ from the inconsistent instance. On this basis, the minimality condition on repairs can be properly formulated. In this monograph we present and discuss these fundamental concepts, different repair semantics, algorithms for computing consistent answers to queries, and also complexity-theoretic results related to the computation of repairs and doing consistent query answering. Table of Contents: Introduction / The Notions of Repair and Consistent Answer / Tractable CQA and Query Rewriting / Logically Specifying Repairs / Decision Problems in CQA: Complexity and Algorithms / Repairs and Data Cleaning

| product details |

| other options |

| back |

| your trolley |

To view the items in your trolley please sign in.

| sign in |

| specials |

The Ballerina and the Bull: Anarchist Utopias in the Age of Finance

Johanna Isaacson
Paperback / softback
288 pages
was: R 306.95
now: R 275.95
This title will take longer to obtain, and should be delivered in 6-8 weeks

Our moment has seen the resurgence of an anarchist sensibility, from the uprisings in Seattle in 1999 to the Occupy movement of 2011.

| more |

| add to trolley |

Fifteen Dogs

AndrÃ© Alexis
Paperback / softback
176 pages
was: R 280.95
now: R 252.95
Available from overseas. Dispatched in aprox 4-8 weeks as local supplier is out of stock

A pack of dogs are granted the power of human thought - but what will it do to them? A surprising and insightful look at the beauty and perils of consciousness.

| more |

| add to trolley |

Bonsai Success in Southern Africa

Carl Morrow
Paperback / softback
160 pages
was: R 320.95
now: R 288.95
Stock is usually dispatched in 6-12 days from date of order

In this uniquely Southern African book, Carl Morrow and Keith Kirsten guide readers step by step into the magical realms of bonsai as a hobby, horticultural practice and art form.

| more |

| add to trolley |