FAQ on Queueing Theory

FAQ=frequently asked questions
Last updated: June, 2006.

Q: What is a queue and what is queueing thory?

A: According to The American College Dictionary, a queue (as a noun) is (1) a braid of hair worn hanging down behind, (2) a file or line of persons, etc.
As a verb, "to queue" means to form a line while waiting for something.
The etymology is from the Latin coda, meaning tail.
QUEUEING THEORY is the mathematical study of waiting lines.
For a further discussion of queueing theory, go to "Definitions of Queueing Theory".

Q: What is the proper spelling -- "queueing" or "queuing?"

A: They are both correct spellings. The vast majority of queueing theory researchers use "queueing." On the other hand, most American dictionaries and spell checkers prefer the spelling "queuing." The list of well known researchers who use "queueing" includes P. Brill, J.W. Cohen, R. Cooper, D.R. Cox, D. Gross, F. Haight, C. Harris, B. Hnedenko, L. Kleinrock, M. Neuts, E. Parzen, N. Prabhu, S. Ross, T. Saaty, L. Takacs, R. Wolff.
In addition, INFORMS, NSERC (Natural Sciences and Engineering Research Council of Canada), CORS (Canadian Operations Research Society), and the journal Queueing Systems: Theory and Applications, all use "queueing" in their publications.
For an interesting set of letters and comments on the two spellings, see OR/MS Today (October, 1992, p. 10 and December, 1992, p. 10).
One of the special features of the spelling QUEUEING is that it has five consecutive vowels (the other words with lots of vowels are obscure: like miaoued, iouea, euouae (6), uoiauai (7). See
http://members.aol.com/gulfhigh2/words6.html for additional information.

Q: What are some of the applications of queueing theory?

A: Queueing theory is useful in telecommunications, traffic control, determining the sequence of computer operations, predicting computer performance, health services (eg. control of hospital bed assignments), airport traffic, airline ticket sales, the mining industry, layout of manufacturing systems. It is even useful in determining when to remove a goalie in a hockey game.

When did mathematical queueing theory start?

Agner Krarup Erlang (ref. An Introduction to Queueing Theory, by Kashyap and Chaudhry, 1988, p. 1) published his first paper on the subject in 1909 (according to Cooper, Introduction to Queueing Theory (Second Edition), 1981). Erlang was an Danish engineer who worked for the Copenhagen Telephone Exchange. Although Erlang was preceded slightly by work of Johannsen (1907), Erlang is still considered the father of mathematical queueing theory. A good summary of the history of queueing theory up to 1961 can be found in Saaty's Elements of Queueing Theory, 1961, pp. 20-25. Also see Syski's article in the book Frontiers in Queueing (1997).