United States Imagery System (USIS) Architecture
The Central Imagery Office [CIO] developed the United States Imagery System (USIS) architecture as an enterprise model to share data, services, and resources. Following the Internet and Intelink concept, data sharing allows organizations to exchange imagery, products, and related support data. Data sharing is a prerequisite to service sharing across the enterprise, and both data and service sharing are prerequisites to resource sharing. Resource sharing allows components to use the resources that are distributed throughout the enterprise. Based on generic organization types, the organizational architecture is a means of defining required services, data types, and information flows. USIS organizations' missions, required information, produced information, and required performance within timelines drive the architecture's technical needs. The technical architecture contains bundles of common functionality and standardization interface points. It expresses needs independent from capabilities, allowing for technical requirements definition. Elements are technical building blocks defined by the services that they provide. The integrated architecture defines the complete USIS by assigning elements to organization types and allowing for variable performance between elements and organizations.
The USIS elements (Collection, Processing, Exploitation, Dissemination, Archive, Management, Site Infrastructure, and Global Communications) are the building blocks of the technical architecture. These elements are defined in terms of the services they provide, the interfaces they support, and their performance. The interfaces describe the points at which interoperability is achieved through standards.
The distinctive feature of USIS 2000 is its independence from fielded systems. Unlike a traditional architectural view which describes the connectivity between specific systems and types of equipment, USIS 2000 describes an architecture based upon an arbitrary collection of systems and components that communicate, provide services and exchange information in prescribed ways. How many systems are fielded and where these systems are located relative to one another establish capability and utility, but are not valid architectural descriptors since resources can be modified or added wherever needed without changing the underlying architecture or interrupting the ability the transfer information. Only when the interfaces between elements are changed is the baseline architecture affected.
The idea behind the USIS 2000 is analogous to the plug and play convenience of the internet. The internet is a collection of disparate equipment of varying capabilities at fixed and mobile locations. The equipment and its locations are constantly in flux; however, new technologies such as cellular connectivity and personal digital assistants are added with relative ease. No one can accurately list all the equipment that exists around the world, nor construct a comprehensible wiring diagram to describe its architecture. Despite this seemingly chaotic situation, the internet has an architectural stability that can be described in terms of standards specifying the protocol stack and data structures required to communicate and transfer information. The USIS 2000, like the internet, is system-independent; the key to plug and play interoperability.
With the formation of NIMA in October 1996, the USIS Architecture was replaced by the United States Imagery and Geospatial Information Systems Architecture [USIGS].
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