Real-Time Innovations, Inc. Copyright © 2007 8
In business, many forces, including the rise of outsourcing, the need for business
agility, and the trend towards “on-demand” business, are leading to scenarios
where independently developed systems must be quickly adapted and re-
adapted to realize new business capabilities.
The new emerging class of distributed applications is an integrated “system-of-
systems” (SoS), that brings together multiple independent systems to provide
new capabilities. In general, the different classes of systems form a continuum;
however for the purposes of this paper we broadly classify systems into three
categories, below.
1. Edge systems. These are systems that touch the “real-world” to perform
various functions, including sensing, and actuation. Often, these systems
must operate under “real-time” constraints---i.e. their correct operation
depends on meeting critical design requirements and timing constraints for
various functions. The timescale is at machine-level, sometimes in the
order of microsecond resolution. Examples of edge systems include
instrumentation, robots, radars, communication equipment etc.
2. Enterprise systems. These are the “information technology” (IT) systems
that traditionally include functions such as high-level user interaction,
decision support, storage and retrieval of historical data. Often these
systems provide the executive-level operational “dashboards” that
integrate data from edge systems. Usually, these systems have “soft” real-
time constraints, and the timescale is at a “human” response level in the
order of seconds, minutes, hours, days, etc. Examples of enterprise
systems include application servers, packaged applications, web-servers
etc.
3. Systems-of-Systems (SoS). These are distributed systems composed of
many Edge, and/or Enterprise systems, including other SoS. Successful
examples of SoS include the “World-Wide-Web (WWW)”, and “electronic
mail”, that run on the public Internet. The US DoD’s GiG is envisioned as a
SoS that integrates various DoD assets over the DoD’s private internet.
SoS are loosely coupled, with many independent entry points, under independent
control domains, that effectively inter-operate to realize multiple objectives.