Operating Systems and Middleware: Supporting Controlled Interaction

From the introduction:

Suppose you sit down at your computer to check your email. One of the
messages includes an attached document, which you are to edit. You click
the attachment, and it opens up in another window. After you start edit-
ing the document, you realize you need to leave for a trip. You save the
document in its partially edited state and shut down the computer to save
energy while you are gone. Upon returning, you boot the computer back
up, open the document, and continue editing.
This scenario illustrates that computations interact. In fact, it demon-
strates at least three kinds of interactions between computations. In each
case, one computation provides data to another. First, your email program
retrieves new mail from the server, using the Internet to bridge space. Sec-
ond, your email program provides the attachment to the word processor,
using the operating system’s services to couple the two application pro-
grams. Third, the invocation of the word processor that is running before
your trip provides the partially edited document to the invocation running
after your return, using disk storage to bridge time.
In this book, you will learn about all three kinds of interaction. In all
three cases, interesting software techniques are needed in order to bring the
computations into contact, yet keep them sufficiently at arm’s length that
they don’t compromise each other’s reliability. The exciting challenge, then,
is supporting controlled interaction. This includes support for computations
that share a single computer and interact with one another, as your email
and word processing programs do. It also includes support for data storage
and network communication. This book describes how all these kinds of
support are provided both by operating systems and by additional software
layered on top of operating systems, which is known as middleware.