One and only one
From Academic Kids
A principle, especially in software development, that values avoiding the hazards of redundancy. Duplication
- increases the difficulty of change,
- may decrease clarity, and
- leads to opportunities for inconsistency.
In mathematics and logic, the phrase "there is one and only one" is associated with unique existence, i.e. the unique existential quantifier, represented by the symbol ∃! .
See external link: Once And Only Once (http://c2.com/cgi/wiki?OnceAndOnlyOnce)
