Trait's for Codd's Relational Calculus?

Before I re-invent the wheel: Has anybody written larch traits for
relational tables with select, join, insert, etc?

I think the original articles were:

       author =       "E. F. Codd",
       title =        "A Relational Model of Data for Large Shared Data
       journal =      "Comm. of the ACM",
       volume =       "13",
       number =       "6",
       pages =        "377",
       month =        jun,
       year =         "1970",
       keywords =     "CACM",
       note =         "Reprinted in M. Stonebraker, Readings in Database
                      Sys., Morgan Kaufmann, San Mateo, CA, 1988",

       author =       "E. F. Codd",
       title =        "Relational Database: {A} Practical Foundation for
       journal =      "Comm. of the ACM",
       volume =       "25",
       number =       "2",
       pages =        "109",
       month =        feb,
       year =         "1982",
       keywords =     "CACM",

Then, on to more ambitious theories:
How about transaction mechanisms?

Daniel W. Connolly        "We believe in the interconnectedness of all things"
Research Scientist, MIT/W3C     PGP: EDF8 A8E4 F3BB 0F3C  FD1B 7BE0 716C FF21 
<connolly@w3.org>                  http://www.w3.org/pub/WWW/People/Connolly/