Confluence

In geography, a confluence is the meeting of two or more bodies of water. Also known as a conflux, it refers either to the point where a tributary joins a larger river, called the main stem, or where two streams meet to become the source of a river of a new name, such as the confluence of the Monongahela and Allegheny rivers in Pittsburgh, Pennsylvania creating the Ohio River.

The term is also used to describe the meeting of tidal or other non-riverine bodies of water, such as two canals or a canal and a lake. A one-mile (1.6 km) portion of the Industrial Canal in New Orleans accommodates the Gulf Intracoastal Waterway and the Mississippi River-Gulf Outlet Canal; therefore those three waterways are confluent there.

Notable confluences

Confluence (convention)

Confluence is an annual science fiction convention that has been occurring in Pittsburgh for several years since 1996. Confluence 2009 was held in the Doubletree Hotel from July 24–26, 2009.

History

Confluence has been in existence for many years. The ninth annual convention garnered over 400 science fiction fans in 1996. The original name was derived from the meaning of Confluence, a gathering, and the fact that Pittsburgh is at the confluence of three rivers.

Events

Confluence is a smaller convention, focused primarily on the literature and art of science fiction. Events include panel discussions, talks, poetry readings, filk concerts, a video room, and more.

References

External links

Confluence (abstract rewriting)

In computer science, confluence is a property of rewriting systems, describing which terms in such a system can be rewritten in more than one way, to yield the same result. This article describes the properties in the most abstract setting of an abstract rewriting system.

Motivating examples

The usual rules of elementary arithmetic form an abstract rewriting system. For example, the expression (11 + 9) × (2 + 4) can be evaluated starting either at the left or at the right parentheses; however, in both cases the same result is obtained eventually. This suggests that the arithmetic rewriting system is a confluent one.

A second, more abstract example is obtained from the following proof of each group element equalling the inverse of its inverse:

This proof starts from the given group axioms A1-A3, and establishes five propositions R4, R6, R10, R11, and R12, each of them using some earlier ones, and R12 being the main theorem. Some of the proofs require non-obvious, if not creative, steps, like applying axiom A2 in reverse, thereby rewriting "1" to "a⁻¹ ⋅ a" in the first step of R6's proof. One of the historical motivations to develop the theory of term rewriting was to avoid the need for such steps, which are difficult to find by an unexperienced human, let alone by a computer program.