What Happened to Theory Anyway?

1
What Happened to Theory Anyway?

• Role of Theory
• What Makes a Good Theory?
• Prospects

2
The 2 Most Annoying Things I Like to Say

1. Theoreticians stop playing games and start
   worrying about what this stuff is good for.
2. Implementers take a little time to appreciate
   the theory in the area where you are about to
   create a major hack.

3
Example Universal Relation

• There is a theory about what happens when you
  imagine that all your relations are projections
  of a single relation.
• Some things become simpler (natural joins, e.g.)
  other things become harder.
• Ted Codd hated the idea.
• Rule 217 Thou shalt not use the ideas of
  Maier-Ullman-Vardi.

4
UR --- (2)

• Whatever you may think of the idea, it keeps
  getting rediscovered.
• Moshe Vardi kept a file of over a dozen papers
  that thought they had discovered a remarkable,
  new interface to databases.
• Good example of why it pays to learn the theory
  before you proceed.

5
But Theory is no Less Guilty

• Confession Ive been guilty of at least the
  following
• Working on stuff just because it is fun.
• Or so that I could get a paper out and maybe
  tenure.
• Or to impress my friends.

6
What Makes a Good Theory?

• The first test is always whether it accomplishes
  something important.
• But theories take a long time to develop.
• Incremental work OK here.
• Decide where to put effort by cleanliness
  theory should offer a high ratio of power to
  mechanism.

7
Example Relational Model

• The relational model is the best example by far
  in our field.
• One basic construct.
• Good for anything.
• Perfect for almost nothing.

8
Example Database logic

• We thought Datalog was going to take over for
  SQL it didnt.
• But it is natural and clean, and the study turned
  out to be worth the effort --- for reasons we
  didnt anticipate.
• Prolog baroque execution model.
• AI/logic way too much mechanism.

9
Application Information Integration

• Logical rules seem better tuned to data
  transformation than querying.
• name(XY) - first(X) last(Y)
• Work of Halevy, collaborators, many others.

10
Application Data Exchange

• Work of Fagin, Kolaitis, c.
• Data sharing, peer-to-peer.
• Uses not only logic, but related dependency
  theory and also some ideas from the
  universal-relation theory.

11
Application Software Security

• Work of Monica Lam, c.
• Datalog to express program analysis.
• More than rules --- stratified negation, e.g.
• Datalog compiled into BDDs to exploit regularity
  in data.
• Atypical for normal databases.

12
Application Networks

• Work of Hellerstein c.
• Describes network properties and constraints in
  Datalog.
• Clean, succinct descriptions of network
  protocols.
• Rapid prototyping.

13
Future

• Funny data models.
• I mean XML.
• Data with regularity.
• Is there more to BDDs as a database
  implementation?
• Data mining.
• Lets get those terrorists.

14
Tree/Graph Data Models

• It seems very hard to switch from relations to
  semistructured data models.
• Which seem rather clean at first face.
• Is there a compromise that will give us the
  composability of relational algebra clean
  queries in the Datalog (or even SQL) style?

15
Structure Within Data

• BDDs work for apps when the data has regularity.
• Aside BDDs are a notation for boolean functions
  that are terrible except for the functions one
  actually cares about.
• BDDs have good algorithms for relational algebra
  operations.
• Can the technique carry over to challenging DB
  apps, e.g., design DBs?

16
Data Mining

• Database systems offers an under-appreciated view
  of data mining its queries, not building
  statistical models.
• Example given a set of numbers, compute AVG, not
  the mean of the most likely Gaussian
  distribution.
• Move beyond association rules.

17
Data Mining on Steroids

• Biggest data-mining problem track terrorism
  while protecting privacy.
• Petabytes of unstructured data.
• x phoned y z bought ammonium nitrate with credit
  card c.
• Algorithms for multijoin queries that cant
  possibly be evaluated fully.

18
Thanks

• While its terrific to receive an award like
  this, it really acknowledges the work of students
  and colleagues who developed the ideas and those
  who, in the fullness of time, put them into
  practice.