Contextual Query Language (CQL), previously known as Common Query Language, is a

formal language In logic, mathematics, computer science, and linguistics, a formal language consists of words whose letters are taken from an alphabet and are well-formed according to a specific set of rules. The alphabet of a formal language consists of s ...

for representing queries to information retrieval systems such as

search engine A search engine is a software system designed to carry out web searches. They search the World Wide Web in a systematic way for particular information specified in a textual web search query. The search results are generally presented in a ...

s, bibliographic catalogs and

museum A museum ( ; plural museums or, rarely, musea) is a building or institution that cares for and displays a collection of artifacts and other objects of artistic, cultural, historical History (derived ) is the systematic study and th ...

collection information. Based on the

semantics Semantics (from grc, σημαντικός ''sēmantikós'', "significant") is the study of reference, meaning, or truth. The term can be used to refer to subfields of several distinct disciplines, including philosophy, linguistics and compu ...

Z39.50 Z39.50 is an international standard client–server, application layer communications protocol for searching and retrieving information from a database over a TCP/IP computer network, developed and maintained by the Library of Congress. It i ...

, its design objective is that queries be human readable and writable, and that the language be intuitive while maintaining the expressiveness of more complex

query language Query languages, data query languages or database query languages (DQL) are computer languages used to make queries in databases and information systems. A well known example is the Structured Query Language (SQL). Types Broadly, query language ...

s. It is being developed and maintained by the Z39.50 Maintenance Agency, part of the

Library of Congress The Library of Congress (LOC) is the research library that officially serves the United States Congress and is the ''de facto'' national library of the United States. It is the oldest federal cultural institution in the country. The librar ...

Examples of query syntax

Simple queries: dinosaur "complete dinosaur" title = "complete dinosaur" title exact "the complete dinosaur" Queries using

Boolean logic In mathematics and mathematical logic, Boolean algebra is a branch of algebra. It differs from elementary algebra in two ways. First, the values of the variables are the truth values ''true'' and ''false'', usually denoted 1 and 0, whereas in ...

: dinosaur or bird Palomar assignment and "ice age" dinosaur not reptile dinosaur and bird or dinobird (bird or dinosaur) and (feathers or scales) "feathered dinosaur" and (yixian or jehol) Queries accessing publication indexes: publicationYear < 1980 lengthOfFemur > 2.4 bioMass >= 100 Queries based on the proximity of words to each other in a document: ribs prox/distance<=5 chevrons ribs prox/unit=sentence chevrons ribs prox/distance>0/unit=paragraph chevrons Queries across multiple

dimensions In physics and mathematics, the dimension of a mathematical space (or object) is informally defined as the minimum number of coordinates needed to specify any point within it. Thus, a line has a dimension of one (1D) because only one coord ...

: date within "2002 2005" dateRange encloses 2003 Queries based on

relevance Relevance is the concept of one topic being connected to another topic in a way that makes it useful to consider the second topic when considering the first. The concept of relevance is studied in many different fields, including cognitive sc ...

: subject any/relevant "fish frog" subject any/rel.lr "fish frog" The latter example specifies using a specific

algorithm In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing ...

for

logistic regression In statistics, the logistic model (or logit model) is a statistical model that models the probability of an event taking place by having the log-odds for the event be a linear function (calculus), linear combination of one or more independent var ...

.Relevance Ranking Context Set version 1.1

References

External links

*
Z39.50 Maintenance Agency
at the Library of Congress

Information retrieval systems Library science Library of Congress Query languages Knowledge representation languages {{LOC-stub