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information technology

Government Electronics & Information Technology Association (GEIA)

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Government Electronics & Information Technology Association
2500 Wilson Boulevard, Arlington, VA 22201-3834
703-907-7566
FAX 703-907-7968

A Sector of the Electronic Industries Alliance (EIA).

In March 2007 ITAA President Phil Bond expressed his desire in merging ITAA with another high tech trade association. [2] On January 17, 2008, ITAA announced that it had agreed to so-called "merger of equals" with the Government Electronics and Information Technology Association (GEIA), and that the combined association would retain the ITAA name.

Cray Inc.

Entity-Relationship Model

In software engineering, an entity-relationship model (ERM) is an abstract and conceptual representation of data. Entity-relationship modeling is a database modeling method, used to produce a type of conceptual schema or semantic data model of a system, often a relational database, and its requirements in a top-down fashion. Diagrams created by this process are called entity-relationship diagrams, ER diagrams, or ERDs.

The definitive reference for entity-relationship modelling is Peter Chen's 1976 paper[1]. However, variants of the idea existed previously, and have been devised subsequently.[2]

[1] "The Entity Relationship Model: Toward a Unified View of Data".

[2] A.P.G. Brown, "Modelling a Real-World System and Designing a Schema to Represent It", in Douque and Nijssen (eds.), Data Base Description, North-Holland, 1975, ISBN 0-7204-2833-5

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The first stage of information system design uses these models during the requirements analysis to describe information needs or the type of information that is to be stored in a database. The data modeling technique can be used to describe any ontology (i.e. an overview and classifications of used terms and their relationships) for a certain area of interest. In the case of the design of an information system that is based on a database, the conceptual data model is, at a later stage (usually called logical design), mapped to a logical data model, such as the relational model; this in turn is mapped to a physical model during physical design. Note that sometimes, both of these phases are referred to as "physical design".

There are a number of conventions for entity-relationship diagrams (ERDs). The classical notation mainly relates to conceptual modeling. There are a range of notations employed in logical and physical database design, such as IDEF1X.

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An entity may be defined as a thing which is recognized as being capable of an independent existence and which can be uniquely identified. An entity is an abstraction from the complexities of some domain. When we speak of an entity we normally speak of some aspect of the real world which can be distinguished from other aspects of the real world.[3]
An entity may be a physical object such as a house or a car, an event such as a house sale or a car service, or a concept such as a customer transaction or order. Although the term entity is the one most commonly used, following Chen we should really distinguish between an entity and an entity-type. An entity-type is a category. An entity, strictly speaking, is an instance of a given entity-type. There are usually many instances of an entity-type. Because the term entity-type is somewhat cumbersome, most people tend to use the term entity as a synonym for this term.
Entities can be thought of as nouns. Examples: a computer, an employee, a song, a mathematical theorem. Entities are represented as rectangles.

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A relationship captures how two or more entities are related to one another. Relationships can be thought of as verbs, linking two or more nouns. Examples: an owns relationship between a company and a computer, a supervises relationship between an employee and a department, a performs relationship between an artist and a song, a proved relationship between a mathematician and a theorem. Relationships are represented as diamonds, connected by lines to each of the entities in the relationship.

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Entities and relationships can both have attributes. Examples: an employee entity might have a Social Security Number (SSN) attribute; the proved relationship may have a date attribute. Attributes are represented as ellipses connected to their owning entity sets by a line.

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Every entity (unless it is a weak entity) must have a minimal set of uniquely identifying attributes, which is called the entity's primary key.

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Entity-relationship diagrams don't show single entities or single instances of relations. Rather, they show entity sets and relationship sets. Example: a particular song is an entity. The collection of all songs in a database is an entity set. The eaten relationship between a child and her lunch is a single relationship. The set of all such child-lunch relationships in a database is a relationship set. In other words, a relationship set corresponds to a relation in mathematics, while a relationship corresponds to a member of the relation.

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Certain cardinality constraints on relationship sets may be indicated as well.

Information Technology Association of America (ITAA)

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From http://www.itaa.org/newsroom/headline.cfm?ID=3023:

09-Dec-08

ITAA Contact - Charlie Greenwald, cgreenwald@itaa.org

The Boards of Directors of AeA (formerly the American Electronics Association) and the Information Technology Association of America (ITAA) have approved the merger of the two trade associations' memberships and programs. The combined associations will become The Technology Association of America. The merger, which will close by the end of the year, will give rise to a stronger voice for the technology industry by bringing together the largest number of tech companies throughout the United States.

General Dynamics

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From http://www.generaldynamics.com/:

Defense industry contractor for shipbuilding and marine systems, defense systems, land and amphibious combat systems and munitions

From Wikipedia: General Dynamics:

General Dynamics Corporation is a U.S. defense conglomerate formed by mergers and divestitures, and as of 2008 it is the fifth largest defense contractor in the world. The company has changed markedly in the post-Cold War era of defense consolidation. The company has four main business segments: Marine Systems, Combat Systems, Information Systems and Technology, and Aerospace. The company's former Fort Worth Division manufactured the F-16 Fighting Falcon, the most-produced Western jet fighter, but that subsidiary was sold to Lockheed in 1993. GD reentered the airframe business in 1999 with their purchase of Gulfstream Aerospace.

Dr. Peter Pin-Shan Chen

Organisation(s)
Related standards/methodologies

The initial approach to IDEF information modeling (IDEF1) was published by the ICAM program in 1981, based on current research and industry needs. The theoretical roots for this approach stemmed from the early work of Edgar F. Codd on relational theory and Peter Chen on the entity-relationship model. The initial IDEF1 technique was based on the work of Dr. R.R. Brown and Mr. T.L. Ramey of Hughes Aircraft and Mr. D.S. Coleman of D. Appleton & Company, with critical review and influence by Charles Bachman, Peter Chen, Dr. M.A. Melkanoff, and Dr. G.M. Nijssen.

Northrop Grumman

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From Wikipedia: Northrop Grumman:

Northrop Grumman Corporation (NYSE: NOC) is an American aerospace and defense technology company formed by the 1994 purchase of Grumman by Northrop. The company was the fourth largest defense contractor in the world in 2008, and the largest builder of naval vessels. Northrop Grumman employs over 122,000 people worldwide. Its 2007 annual revenue is reported at US$32 billion. Northrop Grumman ranks #76 on the 2008 Fortune 500 list of U.S. industrial companies. It is headquartered in Los Angeles, California.

Institute of Electrical and Electronics Engineers (IEEE)