**2. Toward a definition of EC**

The most immediate context for the emergence of edge computation is more general computation and the information sciences. Far from the roots of the abacus, the human "computers" in use during the Babbage age, and the Bletchley mechanical computers of Turing's time, the exponential growth of electronic information processing has been dramatic from the initial solitary transistor to more than 42 million transistors in current integrated circuits, following the prophetic Moore's Law. This has, of course, required an equally significant development of network systems designed by electronic engineers to take advantage of this increase in potential computing power. In the 1950s, electronic engineers began using a fuzzy circular icon in their otherwise very specific circuit design schematics to indicate an important but not specified part of the system, which came to be called the "cloud." This term has been applied as a metaphor in current usage and actually refers to the plethora of data centers using many sophisticated information processing schemes and interconnected by extensive arrays of communication links, including cable and wireless transmission modes. This has been a great opportunity for proprietary interests to market "cloud services," while many individual and corporate users have only a vague and metaphorical awareness of the real physical constituents of the "cloud," which otherwise may seem amorphous and impenetrable.

In truth, the cloud is a market-segmented information processing arrangement that uses the same general technology as more local computation but with a muchenlarged scope and scale. Like its less complex origins in "personal computing," the cloud of course is subject to issues of available computing power and efficient system design. In an effort to establish a specific boundary condition in information processing, the term "edge computing" has enjoyed a similar metaphorical usage functioning as the use of any type of computer program that delivers low latency nearer to requests. Of course, an air-gapped laptop carries out this function without the benefit of network availability. MIT's MTL Seminar, in 2015, defined edge computing broadly as all computing outside the cloud happening at the edge of the network, and more specifically in applications where real-time processing of data is required. In their definition, cloud computing operates on big data while edge computing operates on "instant data," which is real-time data generated by sensors or users. This, of course, begs the question, where is the edge of the cloud? According to The State of the Edge report, edge computing concentrates on servers "in proximity to the last mile network." Alex Reznik, Chair of the ETSI MEC ISG standards committee, loosely defines the term as "anything that is not a traditional data center could be the 'edge' to somebody."

For our purposes, edge computation will be the use of electronic data acquisition, processing, analysis, and actionable feedback with little and intermittent assistance from larger data processing resources. This definition demetaphorizes the use of "cloud" to indicate the use of literally nonlocal system intervention, although contact with larger systems is also a potential use of EC. Later in this chapter, a number of examples of integrated data acquisition, algorithmic analysis, and feedback systems will be described, most of which do not need "cloud services" to function.

The current scale and scope of global overall computing are massive with almost 200 zettabytes predicted by 2025, less than two years hence. With the rapid growth of IoT and particularly the internet of healthy things (IoHT), limitations of centralized data center nodes will become increasingly cumbersome and even prohibitive. The growing use of personal devices including smartphones and wearable devices, as well as smart objects and secure network gateways, will catalyze more autonomous EC. Such development will require a high degree of effective privacy, security and personal data retention, and ownership practices and privileges.
