INTRODUCTION
Digital systems design teams are facing exponentially growing complexities and need processes and tools that reduce the time needed to gain insight into difficult system integration problems.
A digital system is a data technology that uses discrete (discontinuous) values. By contrast, non-digital (or analog) systems use a continuous range of values to represent information. Although digital representations are discrete, the information represented can be either discrete, such as numbers, letters or icons, or continuous, such as sounds, images, and other measurements of continuous systems. The design of digital systems begins with the development of a set of specifications outlining the requirements of the desired system. These specifications are usually composed of block diagram, timing diagrams, flow-charts and natural language. Initial requirements for new digital systems and products that are generally expressed in a variety of notations including diagrams and natural language can be automatically translated to a common knowledge representation for integration, for consistency and completeness analysis, and for further automatic synthesis.
An example of digital system is digital information. All digital information possesses common properties that distinguish it from analog communications methods:
Synchronization: In written or spoken human languages synchronization is typically provided by pauses (spaces), capitalization, and punctuation. Machine communications typically use special synchronization sequences.
Language: All digital communications require a language, which in this context consists of all the information that the sender and receiver of the digital communication must both possess, in advance, in order for the communication to be successful.
Errors: Disturbances in a digital communication do not result in errors unless the disturbance is so large as to result in a symbol being misinterpreted as another symbol or disturb the sequence of symbols. It is therefore generally possible to have an entirely error-free digital communication
Copying: Because of the inevitable presence of noise, making many successive copies of an analog communication is infeasible because each generation increases the noise. Because digital communications are generally error-free, copies of copies can be made indefinitely.
Granularity: When a continuously variable analog value is represented in digital form there is always a decision as to the number of symbols to be assigned to that value. The number of symbols determines the precision or resolution of the resulting datum. The difference between the actual analog value and the digital representation is known as quantization error. This property of digital communication is known as granularity.
Digital integration is the idea that data or information on any given electronic device can be read or manipulated by another device using a standard format. Examples of digital integration are
•Cell phone calendar to public digital calendar (online calendar)
In this example, a user has a cell phone with a calendar, as well as a calendar on the Internet. Digital Integration would allow the user to synchronize the two, and the following features could result:
•The user could plan events and have other users notified. If the Public Digital Calendar is integral with a Blog, then the user could write about the event in it.
•Building services integration for energy management and building control
A home owner or commercial building manager could utilize digital integration products to connect intelligent services within a built environment. An intruder detection or access control system could be used in conjunction with light level sensors to turn lights on and off. So when you walk into a dark room the lights turn on (if you are allowed to be there) and when you leave they turn off behind you, thus making energy savings by preventing lights from being left on.
The same techniques could be used to control HVAC (Heating Ventilation and Air Conditioning) systems. Home owners and commercial building managers can use Web based digital integration to control and manage services within their buildings via a web browser interface. The intelligent controllers in Air Conditioning units for example may be "Web Enabled" using digital integration solutions and products.
The digital revolution is upon us in every form. Computer performance doubles every 18 months. Networks of high performance servers are replacing mainframes at a dizzying pace. Personal communication systems are pervasive, from remote sales tools to medical information systems to networked work group tools. What is behind this 4 Revolution ? This work describes consequences of Integration in digital systems design in terms of their implications in the system integration phase. 5