letters to the editor
Practical Research Yields
Fundamental Insight, Too
Tim Wu’s VieWpOint “Bell Labs and Centralized Inno- vation” (May 2011) was inac- curate regarding a specific example of research at Bell
Wu wrote, “Bell’s scientists did
William Zaumen, Palo Alto, CA
Zaumen is correct. Davisson demonstrated
that all particles, not light, have wave-like
properties; for example, electrons, and even
people, have a wave-like nature. Zaumen is
also correct in saying that Einstein worked
in a field that assumed light was wave-like,
showing its particle-like properties.
Tim Wu, new york
Erik Meijer’s and Gavin Bierman’s article “A Co-Relational Model of Data for
Large Shared Data Banks” (Apr. 2011)
overreached by claiming equivalence
between the Relational Model and
NoSQL “key-value pairs” without regard to the definition of a data model
by E.F. Codd more than 30 years ago.
Finding similarity in NoSQL systems
to some parts of the Relational Model,
Meijer and Bierman mistakenly concluded the two are equivalent.
Codd, in his paper “Data Models in
Database Management” in Proceedings
of the 1980 Workshop on Data Abstraction, Databases and Conceptual Modeling ( http://portal.acm.org/citation.
cfm?id=806891) defined a data model
as comprising three components: data
structures to represent well-formed
expressions in first-order logic; operators closed over these structures,
permitting inferencing; and integrity
constraints to enforce internal consistency.
NoSQL systems have no data model
so defined. All else is commentary.
Meijer and Bierman ignored logic
and inferencing and did not explain
how key-value systems recognize, let
alone enforce, integrity constraints.
They cited referential integrity—a
form of integrity constraint—as an ex-
ogenous cost relational databases bear
to correct for a deficiency. The truth is
actually the opposite; consistency is
a central obligation of any database-
management system. The lack of con-
straint-checking in key-value systems
imposes the constraint-checking bur-
den on the application, a situation the
Relational Model was invented specifi-
cally to correct.
Lowden’s comment contains a number of
errors. Our article was, in fact, explicitly
critical of the lack of an agreed data model
for NoSQL. We didn’t ignore “inferencing,”
proposing instead a query language based
on monad comprehensions—interestingly,
the same query language we prefer for the
relational model. We did not assert that