the relational model are not the same thing; indeed, SQL has little to do with the relational model.) As for “a… type should be an interface that does not name its implementations,” and to the extent we even understand this remark, types in the relational model meet this criterion.

We would never publish a critique of (for example) Hewitt’s actor model without understanding it well; why then does he feel he can publish a critique of the relational model, when he demonstrably does not understand it?

C.J. Date, healdsburg, CA, and

D. mcGoveran, Deerfield Beach, Fl

Reference

1. Date, c.j., Dar wen, h., and lorentzos, n.a. Temporal Data and the Relational Model. morgan kaufmann, san francisco, 2003.

 

Relational model outgrown Unfortunately, Date and McGoveran make no good arguments against the limitations of the relational model, as outlined in my letter (Jan. 2013), partly because we are using incommensurable terminology (such as “negation,” “disjunction,” “concurrency,” and “abstraction”); for details, see articles in Proceedings of Inconsistency Robustness 2011 ( http://robust11.org), especially regarding the requirement for inconsistency robustness. My point is not to dismiss relational databases as a failure but to build on their success and overcome their limitations.

Such an effort must meet several requirements:

Compatibility. All capabilities of current relational databases must continue to be implemented; in addition, incrementally integrating inconsistent information from multiple relational databases with incompatible schemas (something awkward in the relational model) must become standard practice; and

Natural language + gestures (as lingua
franca for communication with computer
systems). Semantics of natural language
and coordinated gestures of multiple
participants must be expressible. An
important consequence is expressions
and gestures must be able to mutu-
ally refer to each other, something
awkward in the relational model; for ex-
ample, if Alice points her finger at Bob
and charges, “I accuse you of harassing
me,” and Bob retorts, “I deny it!,” then
the mutual co-reference of language
and gesture must be expressible.

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Reference

1. hewitt, c. Tutorial for ActorScript. arxiv. cornell university, Ithaca, ny, mar. 2013; http://arxiv.org/ abs/1008.2748

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