Recent Developments in Database Technology: Type Inheritance & Temporal Data (Type Inheritance & T)

Venue: Jurys Great Russell Street Hotel

Location: London, United Kingdom

Event Date/Time: Mar 19, 2003 End Date/Time: Mar 21, 2003
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The overall objective in both cases is to provide a careful explanation of the foundations of the technology in question; thus, the primary focus throughout is on concepts, principles, and theory, rather than on commercial products. However, practical implications are of course discussed wherever appropriate.

Seminar Outline

Part I: Type Inheritance

The concepts of subtyping and type inheritance have been around for many years (especially in the object world); indeed, languages and products supporting those concepts, in one form or another, have also been available in the marketplace for some considerable time. Yet there is no consensus on any well-defined (i.e., formal, abstract, robust, and rigorous) model of inheritance with the consequence that those existing languages and products are all ad hoc to a degree, and they all exhibit surprising (and indeed undesirable) behaviour on occasion. By contrast, Part I of this seminar presents a model of inheritance that certainly is "formal, abstract, robust, and rigorous" (and not ad hoc)i.e., one that does not suffer from the shortcomings of previous approaches.

1. Basic Concepts
· Preliminaries
· Subtypes and supertypes
· Type hierarchies
· Structural vs. behavioral inheritance
· Declared vs. most specific type
· Polymorphism and substitutability

2. Some Implications of these Ideas
· Assignments and comparisons
· Covariance and contravariance
· Changing type
· Mutability

3. Some Questions
· What does inheritance mean?
· The "3 out of 4 rule"
· Read-only vs. update operators
· Code reuse and program immunity

4. Additional Topics
· Signatures
· Union and dummy types
· The Tony Blair problem
· Specialization by constraint
· Object IDs undermine inheritance!
· The 3 out of 4 "rule"
· Subtables and supertables
· Multiple inheritance:
logically required!
· Tuple and relation inheritance:
logically required!
· SQL support

Part II: Temporal Data

Thanks to the ever-decreasing cost of storage and the advent of data warehouse technology, the idea of maintaining historical data has become not just a goal but a reality for many organizations. As a consequence, the ability to deal properly with the time dimension is becoming increasingly important. Yet today's database management systems offer absolutely nothing to help with this important requirement. What is more, the research community has largely failed in this regard as well. Help is on its way, however. The second part of this seminar describes an approach to the problem that looks set to address the (surprisingly complicated!) issue of proper support for temporal databases - an approach that, let it be said immediately, fits squarely into the classical relational framework.

1. A Review of Relational Concepts
· The running example
· Data types
· Relation values and variables
· Integrity constraints
· Relational operators

2. Laying the Foundations
· Time and the database
· What's the problem?
· Intervals
· Interval operators
· Set operators
· The PACK and UNPACK operators
· Relational operators

3. Building on the Foundations
· Database design
· Keys and related constraints
· General constraints
· Database queries
· Database updates
· Stated and logged times
· Point and interval types


The seminar is aimed primarily at technical specialists, not managers, though managers should benefit from it too (most of the technical material needed to understand the overall message is included in the seminar itself). Attendees will be expected to be professionally interested in database management. Thus, the target audience includes (but is not limited to):

· DBMS designers, implementers, and other vendor personnel
· Database consultants
· Data and database administrators
· Information modellers and database designers
· Database application designers and implementers
· Data warehouse personnel
· Computer science professors specializing in database matters
· People responsible for DBMS product evaluation and acquisition

Prior attendance at the seminar Relational Remodelled is highly recommended.

Learning Objectives

On completion of this seminar, attendees will:

· Understand the key principles of type inheritance and see just how existing languages, including the SQL standard and many object languages, typically fail to support those principles

· Understand the complexities of temporal database support, and appreciate the benefits of a truly relational approach to the problem


Chris Date

C. J. Date is an independent author, lecturer, researcher, and consultant, specializing in relational database technology. He is best known for his book An Introduction to Database Systems (seventh edition published in 2000), which has sold well over 650,000 copies and is used by several hundred colleges and universities worldwide. He is also the author of many other books on database management, including most recently Foundation for Future Database Systems: The Third Manifesto (2nd edition, coauthored with Hugh Darwen); The Database Relational Model: A Retrospective Review and Analysis; WHAT Not HOW: The Business Rules Approach to Application Development (all published by Addison-Wesley in 2000); and Temporal Data and the Relational Model (coauthored with Hugh Darwen and Nikos A. Lorentzos, published by Morgan Kaufmann in 2003). Mr. Date enjoys a reputation that is second to none for his ability to communicate complex technical subjects in a clear and understandable fashion.


16-22 Great Russell Street
United Kingdom

Additional Information

Speaker: Chris Date £1145 + VAT = £1345.38