Acronym it. This has become such a problem that it is even evaluated at the level of medical academies such as the American Academy of Dermatology. Acronyms are often taught as mnemonic devices, for example in physics the colors of the visible spectrum are said to be "ROY G. BIV" ("red-orange-yellow-green-blue-indigo-violet"). They are also used as mental checklists, for example in aviation: "GUMPS", which is "Gas-Undercarriage-Mixture-Propeller-Seatbelts". Other examples of mnemonic acronyms are "CAN SLIM", and "PAVPANIC" as well as "PEMDAS". It is not uncommon for acronyms to be cited in a kind of false etymology, called a "folk etymology", for a
Conjunctive query The query evaluation, and thus query containment, is LOGCFL-complete and thus in polynomial time. Acyclicity of conjunctive queries is a structural property of queries that is defined with respect to the query's hypergraph: a conjunctive query is acyclic if and only if it has hypertree-width 1. For the special case of conjunctive queries in which all relations used are binary, this notion corresponds to the treewidth of the dependency graph of the variables in the query (i.e., the graph having the variables of the query as nodes and an undirected edge formula_17 between two variables if and only if there