Ad hoc is a Latin phrase meaning "for this". It generally signifies a solution designed for a specific problem or task, non-generalizable, and not intended to be able to be adapted to other purposes. Compare A priori.
Common examples are organizations, committees, and commissions created at the national or international level for a specific task. In other fields the term may refer, for example, to a military unit created under special circumstances, a tailor-made suit, a handcrafted network protocol, or a purpose-specific equation.
Ad hoc can also mean makeshift solutions, shifting contexts to create new meanings, inadequate planning, or improvised events.
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Ad hoc organizations, including committees and private non-profit organizations, are used when an objective needs consideration and no standing organization or committee within said organization can absorb that issue into its scope. Usually these committees are used on a temporary basis, such as temporary oversight of an issue, or review of the standing rules or the constitution of that organization.
An ad hoc organization may have, in some cases, a long-term or indefinite duration of existence. In these cases, an initial workgroup or forum may give place to a more permanent form of organization. An exaggerated typical example is the OSCE.
Under the Anglo-American Cataloging Rules, ad hoc events such as athletic contests, exhibitions, expeditions, fairs, and festivals are considered to be corporate bodies, and can be used as corporate body access points.
In science and philosophy, ad hoc means the addition of extraneous hypotheses to a theory to save it from being falsified. Ad hoc hypotheses compensate for anomalies not anticipated by the theory in its unmodified form. Scientists are often skeptical of theories that rely on frequent, unsupported adjustments to sustain them. Ad hoc hypotheses are often characteristic of pseudoscientific subjects.[1] Much of Ad hoc hypotheses are not necessarily incorrect, however. An interesting example of an apparently supported ad hoc hypothesis was Albert Einstein's addition of the cosmological constant to general relativity in order to allow a static universe. Although he later referred to it as his "greatest blunder," it has been found to correspond quite well to the theories of dark energy.[2]
Ad hoc querying is a term in information science.
Many application software systems have an underlying database which can be accessed by only a limited number of queries and reports. Typically these are available via some sort of menu, and will have been carefully designed, pre-programmed and optimized for performance by expert programmers.
By contrast, "ad hoc" reporting systems allow the users themselves to create specific, customized queries. Typically this would be via a user-friendly GUI-based system without the need for the in-depth knowledge of SQL, or database schema that a programmer would have.
Because such reporting has the potential to severely degrade the performance of a live system, it is usually provided over a data warehouse.
Ad hoc querying/reporting is a business intelligence subtopic, along with OLAP, data warehousing, data mining and other tools.
In military, ad hoc units are created during unpredictable situations, when the cooperation between different units is needed for fast action. An example would be a military breakout.
The term ad hoc networking typically refers to a system of network elements that combine to form a network requiring little or no planning.