Alberto Mendelzon at Princeton:The Blossoming of Relational

Database Theory

David Maier

Dept. of Computer Science

Portland State University

DB Theory: Toronto to Princeton

• Dennis Tsichritzis (Toronto) goes to IBM Yorktown Heights for the summer to work on OS. Finds database work with Frank King, Don Chamberlin and Ray Boyce more interesting (1973).

• Returns to Toronto, announces to OS group (including Phil Bernstein) that they are now the DB group.

• Phil does PhD on 3NF synthesis (1975), remains at UT as a postdoc.

• Catriel Beeri arrives at Toronto for a postdoc (75-76), shares an office with Phil. Switches from automata to database theory.

The Word Spreads

• Phil goes to Harvard (1976)• Catriel goes to Princeton (1976), teaches DB class,

gets Ullman and Aho interested in relational databases

• Most of Ullman’s PhD students start working on relational database theoryAlberto arrives in Fall 1975, becomes one of the first of

Ullman’s students working on database theory

Main Questions

• Dependency implication+ What kind of dependencies are there?

• What’s a good DB scheme?+ What’s a good a good class of DB schemes?

• When are two DB schemes equivalent?+ What does “equivalent” mean?

• When are two queries equivalent?

Realizations

• 2 3• Not every dependency is an FD• Real DBs aren’t always the projection of a single

instance

First Papers

JDU

AVA

CB

RF

J. Howard

PAB

N. Goodman

YS

MY

1977 1978

We Get Hyper

JDU

AVA

CB

RF

PAB

YS

MY

1977 1978 1979 1980

MYV

FS

AOM

DM

ES

HFK

CHPPH R.E.Ladner

1979-80 Work

• MVDS: Independence of inference axioms• Chase: Tableaux as mappings, tableaux as templates

[MMS]• Equivalence: Same set of fixpoint instances (vs.

embedding equivalent FDs) [BMSU]• Adequacy of decompositions: Distinguishing

Rissanen’s, Arora & Carlson’s notions [MMSU]• Generalized mutual dependencies [MM]

Are We Cyclic Yet?

JDU

AVA

CB

RF

PAB

YS

MY

1977 1978 1979 1980 1981

MYV

FS

AOM

DM

ES

HFK

CHPPH

D.S.Parker

C.Delobel

DSW

1981-2 Topics

• Acyclic database schemes: 9 characterizations end up being equivalent; JD = MVDs [BFMMUY]

• Weak instance model, testing equivalence w/ tableaux

• Equivalence of queries with dependencies [GM]

Need to Stop Somewhere

JDU

AVA

CB

RF

PAB

YS

MY

1977 1978 1979 1980 1981 1982

MYV

FS

AOM

DM

ES

HFK

CHPPH

DSW

M.Casanova

M.Graham

S.Walecka S.Kuck

M.Graham

J.SteinD.Rozenshtein

S.Salveter

1983 & Beyond

Publishing with students at Toronto

Graphical query languages

Deductive databases