kin - A simple relational algebra system

kin is a system intended to evaluate relational algebra expressions, to help people (specifically, me) develop their understanding of and intuitions around relational algebra. It provides functions to load and store data into relations and to evaluate expressions over those relations. It also provides a parser allowing users to write relational algebra expressions in plain text that roughly resemble the traditional notation. kin is not intended to be directly useful as a data querying tool - in particular, it does not make any attempt to represent data in an efficient way, or to perform queries efficiently.

The text syntax

• P[attr1, attr2, ... attrn](expr) -- projection
• S[(attr1 = 'val' AND attr2 = attr3) OR (attr4 = 'val')](expr) -- selection
• R[oldname -> newname, othername->newername](expr) -- rename
• expr U expr -- union
• expr N expr -- intersection
• expr - expr -- difference
• expr * expr -- cartesian product
• expr >< expr -- natural join
• expr / expr -- division

TODO

• A command-line that allows working with relations using the simplified text syntax
• A pretty-printer that converts the simple text syntax into TeX math expressions