  Networked automation systems (NAS) are characterized by confluence of
control, computation, communication and Information (C3I) technologies. Design
decisions of one domain are affected by the constraints posed by others.
Reliable NAS design should address the requirements of the system, and
simultaneously meet the constraints posed by other domains and this is called
co-design in literature. Co-design requires clear definition of interfaces
among these domains. Control design in NAS is affected by the timing
imperfections posed by other domains. In this investigation, we first study the
different sources of timing imperfections in NAS, and classify them based on
their occurrence. The concept of jitter is used to define the timing
imperfections induced by various system components. Using this analysis, we
classify the jitter based on their behavior and domain of occurrence. Our
analysis shows that the jitter induced in NAS can be classified based on domain
as- hardware, software and communication. Next, we use this analysis to model
the jitter from the components of NAS. Modeling timing imperfections helps in
capturing the interfaces among the domains, and we use the concept of design
contracts to capture the interfaces. Design contracts describe the semantic
mapping among the domains and are specified using the jitter margins.
Implementing design contracts requires knowledge of the jitter margin and, the
results from control theory are used to this extent.
