## ONC

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## Ondine

["Concurrency Introduction to an Object-Oriented Language System Ondine", T. Ogihara et al, 3rd Natl Conf Record A-5-1, Japan Soc for Soft Sci Tech, Japan 1986].

Last updated: 2012-12-31

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## one

The lowest positive integer and the basis for counting. Multiplication by one is an identity operator and, since one is its own reciprocal, so is division by one. One is the result of dividing any non-zero number by itself. One raised to any power is one and raising to the power one is also an identity operator.

<data>

The largest digit in binary, related to the value true in Boolean algebra. Digital computers typically represent one by a high voltage and zero by a low voltage.

Last updated: 2012-12-31

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## one-banana problem

<jargon, abuse>

At computer installations where the computers have operators for routine administrivia, the programmers and hardware people tend to look down on the operators and claim that a trained monkey could do their job. The incentives offered to said monkeys would then describe the difficulty of a task. A one-banana problem is simple; hence, "It's only a one-banana job at the most; what's taking them so long?"

Last updated: 2010-03-20

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## one-dimensional array

<types>

An array with only one dimension; the simplest kind of array, consisting of a sequence of items ("elements"), all of the same type. An element is selected by an integer index that normally starts at zero for the first element and increases by one. The index of the last element is thus the length of the array minus one.

A one-dimensional array is also known as a vector. It should not be confused with a list. In some languages, e.g. Perl, all arrays are one-dimensional and higher dimensions are represented as arrays of pointers to arrays (which can have different sizes and can themselves contain pointers to arrays and so on).

A one-dimensional array maps simply to memory: the address of an element with index i is

```	A(i) = A0 + i * s

```
where A0 is the base address of the array and s is the size of storage used for each element, the "stride". Elements may be padded to certain address boundaries, e.g. machine words, to increase access speed, in which case the stride will be larger than the amount of data in an element.

Last updated: 2014-03-22

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## one-line fix

Used (often sarcastically) of a change to a program that is thought to be trivial or insignificant right up to the moment it crashes the system. Usually "cured" by another one-line fix. See also I didn't change anything!

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## one-liner wars

<games, programming>

A game popular among hackers who code in the language APL (see write-only language and line noise). The objective is to see who can code the most interesting and/or useful routine in one line of operators chosen from APL's exceedingly hairy primitive set. A similar amusement was practiced among TECO hackers and is now popular among Perl aficionados.

Ken Iverson, the inventor of APL, has been credited with a one-liner that, given a number N, produces a list of the prime numbers from 1 to N inclusive. It looks like this:

```  (2 = 0 +.= T o.| T) / T <- iN

```
where "o" is the APL null character, the assignment arrow is a single character, and "i" represents the APL iota.

Last updated: 2000-03-19

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## ones complement

A system used in some computers to represent negative numbers. To negate a number, each bit of the number is inverted (zeros are replaced with ones and vice versa). This has the consequence that there are two reperesentations for zero, either all zeros or all ones.

```	...
000...00011 = +3
000...00010 = +2
000...00001 = +1
000...00000 = +0
111...11111 = -0
111...11110 = -1
111...11101 = -2
111...11100 = -3
...

```
Naive logic for ones complement addition might easily conclude that -0 + 1 = +0.

The twos complement avoids this by using all ones to represent -1.

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<security>

(OTP) A security system that requires a new password every time a user authenticates themselves, thus protecting against an intruder replaying an intercepted password. OTP generates passwords using either the MD4 or MD5 hashing algorithms.

The equivalent term "S/Key", developed by Bellcore, is a trademark of Telcordia Technologies, so the name OTP is used increasingly.

See RFC 1760 - "The S/KEY One-Time Password System" and RFC 1938 - "A One-Time Password System".

Last updated: 2000-01-31

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## One Time Programmable Read-Only Memory

<storage>

(OTPROM, EPROM OTP) A kind of storage device like an EPROM but with no quartz glass window in the package for erasing the contents. This reduces the packaging cost but means the device cannot be erased with UV and so can only be written once. Erasure is possible, but expensive, with X-rays.

Last updated: 1995-04-22

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## one-way function

A function which is easy to compute but whose inverse is very difficult to compute. Such functions have important applications in cryptography, specifically in public-key cryptography.

Last updated: 2001-05-10

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## one-way hash function

(Or "message digest function") A one-way function which takes a variable-length message and produces a fixed-length hash. Given the hash it is computationally infeasible to find a message with that hash; in fact one can't determine any usable information about a message with that hash, not even a single bit. For some one-way hash functions it's also computationally impossible to determine two messages which produce the same hash.

A one-way hash function can be private or public, just like an encryption function. MD5, SHA and Snefru are examples of public one-way hash functions.

A public one-way hash function can be used to speed up a public-key digital signature system. Rather than sign a long message, which can take a long time, compute the one-way hash of the message, and sign the hash.

Last updated: 2001-05-10

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## on-line

<jargon>

1. Ready for use. E.g. "The graph plotter's fixed and on-line again".

2. Interactive as opposed to batch. Accessible via a computer (or terminal), rather than on paper or other medium.

3. Of a user, actively using a computer system, especially the Internet. E.g "I haven't been on-line for three days."

"On-line" should be hyphenated because it is compounded from two words but the hyphen is often omitted in names of organisations or services.

Last updated: 1998-12-22

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## On-Line Analytical Processing

<database>

(OLAP) A category of database software which provides an interface such that users can transform or limit raw data according to user-defined or pre-defined functions, and quickly and interactively examine the results in various dimensions of the data.

OLAP primarily involves aggregating large amounts of diverse data. OLAP can involve millions of data items with complex relationships. Its objective is to analyze these relationships and look for patterns, trends, and exceptions.

The term was originally coined by Dr. Codd in 1993 with 12 "rules". Since then, the OLAP Council, many vendors, and Dr. Codd himself have added new requirements and confusion.

Richard Creeth and Nigel Pendse define OLAP as fast analysis of shared multidimensional information. Their definition requires the system to respond to users within about five seconds. It should support logical and statistical processing of results without the user having to program in a 4GL. It should implement all the security requirements for confidentiality and concurrent update locking. The system must provide a multidimensional conceptual view of the data, including full support for multiple hierarchies. Other aspects to consider include data duplication, RAM and disk space requirements, performance, and integration with data warehouses.

Various bodies have attempted to come up with standards for OLAP, including The OLAP Council and the Analytical Solutions Forum (ASF), however, the Microsoft OLE DB for OLAP API is the most widely adopted and has become the de facto standard.

Usenet newsgroup: comp.databases.olap.

[What's a "multidimensional conceptual view"?]

Last updated: 1996-09-24

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## Online Computer Library Center, Inc.

<library>

(OCLC) A nonprofit membership organisation offering computer-based services and research to libraries, educational organisations, and their users. OCLC operates the OCLC Cataloging PRISM service for cataloging and resource sharing, provides on-line reference systems for both librarians and end-users, and distributes on-line electronic journals. OCLC's goals are to increase the availability of library resources and reduce library costs for the fundamental public purpose of furthering access to the world's information. The OCLC library information network connects more than 10,000 36,000 libraries worldwide. Libraries use the OCLC System for cataloguing, interlibrary loan, collection development, bibliographic verification, and reference searching. Their most visible feature is the OCLC Online Union Catalog (OLUC) WorldCat (the OCLC Online Union Catalog).

Last updated: 2000-03-23

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## On-Line Computer system

(OLC) A predecessor of the Culler-Fried System from UCSB ca. 1966.

[Sammet 1969, p.253].

Last updated: 1995-11-25

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## Online Media

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## On-line Process Synthesizer

(OPS) A system for discrete simulation under CTSS developed by M. Greenberger at MIT ca. 1964.

[Sammet 1969, p.660. Versions: OPS-3, OPS-4. "On- line Computation and Simulation: The OPS-3 System", M. Greenberger et al, MIT Press 1965].

Last updated: 2003-04-05

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## Online Public Access Catalog

<library>

(OPAC) A computerised system to catalogue and organise materials in a library (the kind that contains books). OPACs have replaced card-based catalogues in many libraries. An OPAC is available to library users (public access).

Last updated: 2000-07-17

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## On-Line Transaction Processing

<database>

(OLTP) The processing of transactions by computers in real time.

[Details? Products?]

Last updated: 1997-05-14

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## Ontic

<language>

Object-oriented language for an inference system with a Lisp-like appearance, but based on set theory.

["Ontic: A Knowledge Representation System for Mathematics", D.A. McAllester, MIT Press 1989].

Last updated: 1996-06-24

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## onto

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## ontology

1. A systematic account of Existence.

2. (From philosophy) An explicit formal specification of how to represent the objects, concepts and other entities that are assumed to exist in some area of interest and the relationships that hold among them.

For AI systems, what "exists" is that which can be represented. When the knowledge about a domain is represented in a declarative language, the set of objects that can be represented is called the universe of discourse. We can describe the ontology of a program by defining a set of representational terms. Definitions associate the names of entities in the universe of discourse (e.g. classes, relations, functions or other objects) with human-readable text describing what the names mean, and formal axioms that constrain the interpretation and well-formed use of these terms. Formally, an ontology is the statement of a logical theory.

A set of agents that share the same ontology will be able to communicate about a domain of discourse without necessarily operating on a globally shared theory. We say that an agent commits to an ontology if its observable actions are consistent with the definitions in the ontology. The idea of ontological commitment is based on the Knowledge-Level perspective.

3. The hierarchical structuring of knowledge about things by subcategorising them according to their essential (or at least relevant and/or cognitive) qualities. See subject index. This is an extension of the previous senses of "ontology" (above) which has become common in discussions about the difficulty of maintaining subject indices.

Last updated: 1997-04-09

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## OnX

A graphics package from LAL Orsay.

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