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10
Architectural Imperatives for I-2
The efforts to bridge the cyber and physical worlds have progressed along
several directions, as described in Chapter6. Ranging from national and
international initiatives such as smart grid and IPSO Interops to the activi-
ties of hobbyists and do- it- yourselfers, from web- based control of residen-
tial appliances to monitoring individual items in supply chains, the ongoing
endeavors span a broad spectrum. While the vast breadth of activities has
certainly helped stimulate interest, it may have also splintered the focus
of the endeavor. Despite worldwide incubation efforts for nearly a decade
no single initiative has emerged as a clear candidate for, or an embryonic
version of, the envisioned cyber- physical infrastructure. In fact, let alone
an embryonic version of the infrastructure, at present, we do not even have
consensus on a blueprint for the cyber- physical system. There is no global
agreement on what the infrastructure should be, on its denition or its scope.
Instead, characteristic of an endeavor that is yet to reach maturity, there is
a profusion of proposals for the denition, scope, and architecture of the
edgling infrastructure.
Following the terminology used in previous chapters, we will continue
to refer to the emerging cyber- physical infrastructure as Internet 2.0—or
I-2—to separate it from the various models that have been labeled with the
generic term “Internet of Things” in the literature [ IoT- A 2011]. In this chap-
ter we outline the architectural imperatives for I-2, by which we mean the
set of features that must be baked into I-2’s architecture. Our discussion
of the architectural imperatives is guided by the lessons learned from the
Internet and the web. The architectural imperatives are then used to provide
a coarse- grained description of I-2 and its scope. The endpoint of this chapter
is not a proposal for I-2’s architecture. Rather, it is a set of principles that must
be incorporated into I-2, if it is to emerge as a successful Internet- scale infra-
structure. The discussion here will hopefully serve to facilitate convergence
towards a global consensus on I-2’s architecture.
The rest of the chapter is organized as follows. Viewing I-2 as a distrib-
uted complex system, we rst ask and answer the question: what is the right
resolution scale for I-2? The I-2 paradigm encompasses a vast heterogeneity of
physical resources, digital resources, communication protocols, and applica-
tions. While supporting a vast heterogeneity at the edge, à la the Internet, the
core architecture of I-2 must remain essentially simple and homogeneous if
it is to be robust on an Internet- scale. The Internet, and the World Wide Web,
have achieved such simplicity in their core architectures through a judicious

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