The definitions presented in this appendix are architectural terms of reference extracted from the USIGS Glossary [Ugloss98]. They are intended to assist in understanding the architecture, reference model, and standards discussions in the sections of this document.

application
The use of capabilities provided by an information system specific to the satisfaction of a set of user requirements. Note: These capabilities include hardware, software, and data. [IEEE P1003.0]

application platform [entity]
1) A set of resources, including hardware and software, that support the services on which application software will run. The application platform provides services at its interfaces that, as much as possible, make the specific characteristics of the platform transparent to the application software. [IEEE P1003.0]
2) The collection of hardware and software components that provide the services used by support and mission-specific software applications. [TAFIM 3.0]

application program interface (API)
The interface between the application software and the application platform, across which all services are provided. [IEEE P1003.0]

application software
Software that is specific to an application and is composed of programs, data, and documentation. [IEEE P1003.0]

architectural framework
Identifies key interfaces and services, and provides a context for identifying and resolving policy, management and strategic technical issues. Constrains implementation by focusing on interfaces, but does not dictate design or specific technical solutions. [OpenGIS Guide]

architecture
Architecture has various meanings, depending upon its contextual usage. (a) The structure of components, their interrelationships, and the principles and guidelines governing their design and evolution over time. (b) Organizational structure of a system or component. An architecture is a composition of (1) components (including humans) with their functionality defined (Technical), (2) requirements that have been configured to achieve a prescribed purpose or mission (Operational), and (3) their connectivity with the information flow defined (System). [JTA]

architecture of a system
A set of rules that define the structure of a system and inter-relationships between its parts. [RM-ODP]

architecture views
See views, architecture.

Common Facilities {CORBA}
Facilities useful in many application domains and which are made available through OMA- [Object Management Architecture-] compliant class interfaces. [OMA Guide]

Common Object Request Broker Architecture (CORBA)
1) An architecture that enables pieces of programs, called objects, to communicate with one another regardless of what programming language they were written in or what operating system they're running on. CORBA was developed by an industry consortium known as the Object Management Group (OMG). There are several implementations of CORBA, the most widely used being IBM's SOM [System Object Model] and DSOM [Distributed System Object Model] architectures. CORBA has also been embraced by Netscape as part of its Netscape ONE (Open Network Environment) platform. Two competing models are Microsoft's COM [Common Object Model]and DCOM [Distributed Common Object Model] and Sun Microsystems' RMI [Remote Method Invocation]. [PC Webopaedia]
2) An ORB standard endorsed by the OMG (Object Management Group). An ORB is software that handles the communication of messages between objects in a distributed, multi-platform environment. [Freedman 1995]

Common Operating Environment (COE)
See Defense Information Infrastructure Common Operating Environment (DII COE).

Common Support Application (CSA)
CSAs provide the architectural framework for managing and disseminating information flow throughout the system, and for sharing information among applications. CSAs contain facilities for processing and displaying common data formats and for information integration and visualization. [DII COE I&RTS]

component
A stand-alone 'object' that is not bound to a particular program, computer language, or implementation. It is not a complete application, but can be used to build cheap, personalized applications [Shah 1996]

conceptual data model
The relationship and definitions of all data that is used by and influences the other three architecture components - operational, systems, and technical. [UAF-B]

Defense Information Infrastructure Common Operating Environment (DII COE)
The DII COE establishes an integrated software infrastructure which facilitates the migration and implementation of functional mission applications and integrated databases across information systems in the Defense Information Infrastructure (DII). The DII COE provides architecture principles, guidelines, and methodologies that assist in the
development of mission application software by capitalizing on a thorough, cohesive set of infrastructure support services. [DII MP]

Department of Defense Joint Technical Architecture (DoD JTA)
A DoD document designed to provide the minimum set of standards that, when implemented, permit the flow of information in support of the Warfighter. The DoD JTA:

provides the foundation for interoperability among all tactical, strategic, and combat support services systems;

mandates the standards and guidelines for system development and acquisition that will significantly reduce cost, development time and fielding time for improved systems, while minimizing the impact on system performance wherever possible;

communicates to industry DoD's intent to use open systems products and implementations;

reflects the direction of industry's standards-based product development so that today's emerging technologies can be more readily leveraged by tomorrow's military systems. [JTA]

distributed computing
A type of computing in which different components and objects comprising an application can be located on different computers connected to a network. So, for example, a word processing application might consist of an editor component on one computer, a spell-checker object on a second computer, and a thesaurus on a third computer. In some distributed computing systems, each of the three computers could even be running a different operating system. Distributed computing is a natural outgrowth of object-oriented programming. Once programmers began creating objects that could be combined to form applications, it was a natural extension to develop systems that allowed these objects to by physically located on different computers. One of the requirements of distributed computing is a set of standards that specify how objects communicate with one another. There are currently two chief distributed computing standards: CORBA and DCOM. [PC Webopaedia]

distributed processing
1) Also called distributed computing, it is a system of computers connected by a communications network. The term is used loosely to refer to any computers with communications between them. However, in true distributed processing, each computer system is sized to handle its local workload, and the network has been designed to support the system as a whole. [Freedman 1995]
2) Information processing in which discrete components may be located in different places, and where communication between components may suffer delay or may fail. [RM-ODP]

domain
1) A distinct functional area that can be supported by a family of systems with similar requirements and capabilities. An area of common operational and functional requirements. [JTA]
2) A concept important to interoperability, it is a distinct scope, within which common characteristics are exhibited, common rules observed, and over which a distribution transparency is preserved. [CORBA 2.2]
3) System context: A class of systems which have similar requirements and capabilities. Application context: The body of knowledge defining the range and scope of an application in terms of elements, rules and behaviors. [OpenGIS Guide]
4) A set of objects, each of which is related by a characterizing relationship, to a controlling object. Every domain has a controlling object associated with it. Examples of domains are: Security domains and Management domains. [RM-ODP]

emerging standard
A specification that is under consideration by an accredited standards development organization, but that has not completed the process of approval by the sponsoring body. Emerging standards are often subject to significant change prior to approval. [IEEE P1003.0]

entity
1) Representation of a collection of data elements in a conceptual schema. [ISO/TC 211]
2) Class of objects with common properties. [ISO/TC 211]
3) Any concrete or abstract thing of interest. While in general the word entity can be used to refer to anything, in the context of modeling it is reserved to refer to things in the universe of discourse being modeled. [RM-ODP]

facility
A collection of object services, with additional functionality, that is used for a specific purpose. [UTA]

framework
A reusable software template, or skeleton, from which key enabling and supporting services can be selected, configured, and integrated with application code. [OpenGIS Guide] See also architectural framework.

framework {object-oriented}
In object-oriented programming, a generalized subsystem design for building applications. It consists of abstract classes and their object collaboration as well as concrete classes. While object-oriented programming supports software reuse, frameworks support design reuse. [Freedman 1995]

Imagery & Geospatial Community (IGC)
The composition of cooperating commands, services, agencies, and departments within the United States Government, foreign governments, and private sector organizations involved in the acquisition, production and exploitation, and dissemination of imagery, imagery intelligence, and geospatial information. The IGC fosters extensive partnerships with others, including commercial and academic institutions, to collaboratively work together to share information. [NIMA SP]

infrastructure
Infrastructure is used with different contextual meanings. Infrastructure most generally relates to and has a hardware orientation, but note that it is frequently more comprehensive and includes software and communications. Collectively, the structure must meet the performance requirements of and capacity for data and application requirements. Again note that just citing standards for designing an architecture or infrastructure does not include functional and mission area requirements for performance. Performance requirement metrics must be an inherent part of an overall infrastructure to provide performant interoperability and compatibility. It identifies the top-level design of communications, processing, and operating system software. It describes the performance characteristics needed to meet database and application requirements. It provides a geographic distribution of components to locations. The infrastructure architecture is defined by the service provider for these capabilities. It includes processors, operating systems, service software, and standards profiles that include network diagrams showing communication links with bandwidth, processor locations, and capacities to include hardware builds versus schedule and costs. [TAFIM 3.0]

interface
1) A listing of the operations and attributes that an object provides. This includes the signatures of the operations, and the types of the attributes. An interface definition ideally includes the semantics as well. An object satisfies an interface if it can be specified as the target object in each potential request described by the interface. [CORBA 2.2]
2) A connecting link or interrelationship between two systems, two devices, two applications, or the user and an application, device, or system. In the OSI [Open Systems Interconnection] Reference Model, it is the boundary between adjacent layers. [TAFIM 3.0]
3) (a) A shared boundary across which information is passed. (b) A hardware or software component that connects two or more components for the purpose of passing information from one to the other. (c) To connect two or more components for the purpose of passing information from one to the other. (d) To serve as a connecting or connected component as in (a). [IEEE 610.12]
4) A shared boundary between two functional entities. A standard specifies the services in terms of the functional characteristics and behavior observed at the interface. The standard is a contract in the sense that it documents a mutual obligation between the service user and provider and assures stable definition of that obligation. [IEEE P1003.0]

interoperability
1) The ability for a system or components of a system to provide information portability and interapplication, cooperative process control. [OpenGIS Guide]
2) (a) The ability of two or more systems or components to exchange and use information. (b) The ability of systems to provide and receive services from other systems and to use the services so interchanged to enable them to operate effectively together. [TOGAF 3]
3) The ability of the systems, units, or forces to provide and receive services from other systems, units, or forces, and to use the services so interchanged to enable them to operate effectively together. The conditions achieved among communications-electronics systems or items of communications-electronics equipment when information or services can be exchanged directly and satisfactorily between them and/or their users. [JPUB 1-02]

interoperability {CORBA}
The ability for two or more ORBs to cooperate to deliver requests to the proper object. Interoperating ORBs appear to a client to be a single ORB. [CORBA 2.2]

interoperability {DII COE}
The ability of two or more systems or components to exchange and use information (IEEE STD 610.12). This definition is extended in the context of a COE to include levels of interoperability, and relate interoperability to interfacing (lowest, least desirable level) versus true integration (highest, most desirable level). [DII COE I&RTS]

Joint Technical Architecture (JTA)
See Department of Defense Joint Technical Architecture (DoD JTA).

Mission Area Application (MAA)
Mission area applications implement specific end-user requirements or needs (e.g., payroll, accounting, materiel management, personnel, control of real-time systems, analysis of order of battle). [TAFIM 3.0]

object request broker (ORB)
Provides the means by which clients make and receive requests and responses. [CORBA 2.2] See also Common Object Request Broker Architecture (CORBA).

open system
1) A system that implements sufficient open specifications for interfaces, services, and supporting formats to enable properly engineered components to be utilized across a wide range of systems with minimal changes, to interoperate with other components on local and remote systems, and to interact with users in a style that facilitates portability. An open system is characterized by the following:

well defined, widely used, non-proprietary interfaces/protocols, and

use of standards which are developed/adopted by industrially recognized standards bodies, and

definition of all aspects of system interfaces to facilitate new or additional systems capabilities for a wide range of applications, and

explicit provision for expansion or upgrading through the incorporation of additional or higher performance elements with minimal impact on the system. [JTA]

to be ported with minimal changes across a wide range of systems from one or more suppliers;

to interoperate with other applications on local and remote systems;

to interact with people in a style that facilitates user portability. [IEEE P1003.0]

platform
1) Computer hardware, including microcomputers, workstations, and mainframe computers, or for underlying software, like an operating system, that provides services to layered software. When discussing software, platform independence implies the software can be run on any computer. [OpenGIS Guide]
2) The entity of the Technical Reference Model that provides common processing and communication services that are provided by a combination of hardware and software and are required by users, mission area applications, and support applications. [TAFIM 3.0]

profile of a standard
The tailoring of a standard to satisfy a specified need. Tailoring is accomplished by selecting a subset of the standard or by selecting options within the standard. A profile is selected to apply across an application area of a standard rather than across a single application. [USIS 95] Contrast with profile, standards.

profile, standards
A set of one or more base standards, and, where applicable, the identification of chosen classes, subsets, options, and parameters of those base standards, necessary for accomplishing a particular function. [IEEE P1003.0] Contrast with profile of a standard.

public specifications
Specifications that are available, without restriction, to anyone for implementation, sublicensing, and distribution (i.e., sale) of that implementation. [IEEE P1003.0]

reference model
1) A reference model is a generally accepted abstract representation that allows users to focus on establishing definitions, building common understandings and identifying issues for resolution. Reference models provide a mechanism for identifying key issues associated with portability, scalability, and interoperability. [JTA]
2) A structured collection of concepts and their relationships that scope a subject and enable the partitioning of the relationships into topics relevant to the overall subject and that can be expressed by a common means of description. [IEEE P1003.0]

service
1) A function that is common to a number of programs, such as performing some extensive calculation or retrieving a category of data. An example of a service is a function that accepts a request to transform a point from one coordinate system into another. [DII COE I&RTS]
2) A distinct part of the functionality that is provided by an entity on one side of an interface to an entity on the other side of the interface. [IEEE P1003.0]

service area
A set of capabilities grouped into categories by function. The JTA defines a set of services common to DoD information systems. [JTA]

standard
1) A document, established by consensus and approved by an accredited standards development organization, that provides, for common and repeated use, rules, guidelines, or characteristics for activities or their results, aimed at the achievement of the optimum degree of order and consistency in a given context. [IEEE P1003.0]
2) A document that establishes uniform engineering and technical requirements for processes, procedures, practices, and methods. Standards may also establish requirements for selection, application, and design criteria of material. [JTA]

standard (IT)
IT standards provide technical definitions for information system processes, procedures, practices, operations, services, interfaces, connectivity, interoperability, information formats, information content, interchange and transmission/transfer. IT standards apply during the development, testing, fielding, enhancement, and life-cycle maintenance of DoD information systems. IT standards include non-government national or international standards, Federal standards, military standards, and multinational treaty organization standardization agreements. They may take numerous forms including standards, handbooks, manuals, specifications, commercial item descriptions, standardized drawings, all referred to collectively here as standards. [DISA CFS]

standardized profile
A balloted, formal, harmonized document that specifies a profile. [IEEE P1003.0]

standards profile
See profile, standards.

system
1) (a) People, machines and methods organized to accomplish a set of specific functions. (b) An integrated composite of people, products, and processes that provides a capability or satisfy a stated need or objective. [JTA]
2) A collection of components organized to accomplish a specific function or set of functions. [IEEE 610.12]
3) Something of interest as a whole or as comprised of parts. Therefore a system may be referred to as an entity. A component of a system may itself be a system, in which case, it may be called a subsystem. For modeling purposes, the concept of a system is understood in its general, system-theoretic sense. The term "system" can refer to an information processing system but can also be applied more generally. [RM-ODP]
4) A set of different elements so connected or related as to perform a unique function not performable by the elements alone. The most important and distinguishing characteristic of a system, therefore, is the relationships among the elements. [DII COE I&RTS]

systems architecture view
The systems architecture view is a description, including graphics, of systems and interconnections providing for, or supporting, warfighting functions. For a domain, the systems architecture view shows how multiple systems link and interoperate, and may describe the internal construction and operations of particular systems within the architecture. For the individual system, the systems architecture view includes the physical connection, location, and identification of the key nodes (including materiel item nodes), circuits, networks, warfighting platforms, etc., and specifies system and component performance parameters (e.g., mean time between failure, maintainability, availability). The systems architecture view associates physical resources and their performance attributes to the operational view and its requirements per standards defined in the technical architecture. [C4ISR AF]

technical architecture view
The technical architecture view is the minimal set of rules governing the arrangement, interaction, and interdependence of system parts or elements, whose purpose is to ensure that a conformant system satisfies a specified set of requirements. The technical architecture view provides the technical systems-implementation guidelines upon which engineering specifications are based, common building blocks are established, and product lines are developed. The technical architecture view includes a collection of the technical standards, conventions, rules and criteria organized into profile(s) that govern system services, interfaces, and relationships for particular systems architecture views and that relate to particular operational views. [C4ISR AF]

Technical Reference Model (TRM) {DoD}
A target framework and profile of standards for the DoD computing and communications infrastructure. [JTA] See also reference model.

United States Imagery and Geospatial Information System (USIGS)
The extensive network of systems used by the Department of Defense (DoD) and the Intelligence Community that share and exploit imagery, imagery intelligence, and geospatial information. These systems provide capabilities involved with the integrated information management, collection, production, exploitation, dissemination and archive, and infrastructure of this information. Organizations which have some level of interface with USIGS, but are not part of DoD and the Intelligence Community, are considered participants in USIGS if they adhere to the technical and system standards. [NIMA SP]

user
(a) Any person, organization, or functional unit that uses the services of an information processing system. (b) In a conceptual schema language, any person or any thing that may issue or receive commands and messages to or from the information system. [TAFIM 3.0]

views, architecture
Perspectives that logically combine to describe an architecture. [C4ISR AF] See operational architecture view; systems architecture view; technical architecture view. See also conceptual data model.