011_motivation.html

<title>1.1 Motivation</title>

<meta charset="utf-8">

<link rel="stylesheet" href="../style.css">

<link rel="prev" href="0_preface.html">
<link rel="next" href="012_scope.html">

<script src="../script.js"></script>

<h2 id="motivation">1.1 Motivation</h2>

<P>
Computers have been increasingly influencing our lives in the last decades.
Distinct eras of computing have elapsed, driven by technological progress 
and affecting the way we are using computers. These
shifts of paradigms were motivated mostly by advances in hardware and software
technology, but also by changes in the way humans interact with computers.

<P>
The first computers were large machines solely built for dedicated
applications such as numeric computations. There was no real distinction between
software and hardware, and new applications could not be executed without
changing the physical configuration. The instructions were executed directly without
any operating systems underneath and the program had direct access to
all system resources. Also, there was no interaction between the
running program and the user. 
With the advent of punch cards and batch processing, computers became more
flexible tools for processing jobs. 
Not just data--executable programs, too--were now used as input,
defined in low-level, imperative languages.
There
was still no interaction during execution and jobs could only be executed
sequentially.

<P>
Machines were expensive but in great demand. The next innovations were
thus influenced by concepts allowing multiple users to work on the same machine and
multiple programs to run at the same time--mainframe computers, operating
systems,  and time-sharing. Terminal-based command line interfaces provided the
first interactive systems. New programming languages such as FORTRAN or ALGOL 
allowed the development of larger and more reliable applications without using pure assembly code.

<P>
The arrival of networking was also the beginning of a new kind of
computing. Distributed applications not just take advantage of the
resources of multiple machines, they also allow the existence of federated systems that consist
of multiple machines remotely located. It promptly became apparent that
in order to support such systems, additional software on top of a network operating system was necessary.
Others favored a distributed operating system which provided a high degree of transparency
and supported migration functions as part of the operating system.
Early middleware systems based on transaction monitors and remote
procedure calls emerged, easing the development of distributed applications.
Existing networks were linked and a global network was formed; the
Internet. The evolution from mainframes to mini computers, then workstations and
personal computers, not just urged networking. It also introduced new user
interaction mechanisms. Consoles were replaced by graphical displays and
enabled more sophisticated forms of interaction such as direct manipulation. 

<P>
At that time, the idea of object-oriented programming arose and quickly gained
much attention. New programming languages such as Simula and Smalltalk
emerged and embraced this principle.
After a short time, objects were also considered as distributable units for
distributed middleware systems.

<P>
The following era of desktop computing was shaped by personal computers, 
growing microprocessor clock speeds, graphical user interfaces and desktop
applications. 
At the same time, the old idea of non-linear information networks was
rediscovered and its first real implementation appeared.
Dating back to Vannevar Bush's MEMEX device and later Ted Nelson's
concept of documents interconnected through hypertext, the WWW
represented a truly novel distributed information architecture in the Internet.

<P>
With the first commercial usage, the WWW scored an instant
success and soon hit a critical mass of users to become the most popular service
within the whole Internet. This also motivated a complete transformation of our
information economy.
Technological advances at that time predicted the rise of mobile computing that
should eventually proceed into an era of ubiquitous computing. 
Computers were not only going to become smaller and smaller, 
but also omnipresent and produced in various sizes and shapes. 
This introduced the notion of calm technology-
-technology
that immerses into everyday life. Ubiquitous computing also heavily changes the
way we are interacting with computers. Multi-modal and implicit interactions are
favored and provide more natural interactions. Devices such as laptops, tablet
computers, pad computers, mobile phones and smartphones have already blurred the
boundaries between different types of computing devices. Combined with wireless
broadband internet access, they have introduced new forms of mobility, providing
connectivity at all times.

<P>
While we are currently on the verge of ubiquitous computing, there are other
trends as well that are influencing the way we think about and do computing right now. 
The progress of microprocessors has saturated in terms of clock cycles due to 
physical constraints. Instead, modern CPUs are equipped with increasing numbers
of cores. This trend has forced developers, architects and language designers to
leverage multi-core architectures. 
The web has already started to oust desktop applications. Modern browsers are becoming
the new operating systems, providing the basic runtime environment for web-based
applications and unifying various platforms. The web is changing and provides
continuously more user-centric services. Being able to handle and process huge
numbers of users is common for social platforms such as Facebook and Twitter
and corporations like Amazon or Google. Hosting such applications challenges
traditional architectures and infrastructures. Labeled as so-called "Cloud
Computing", highly available, commercial architectures emerged. They are built on large clusters
of commodity hardware and enable applications to scale with varying demand
over time on a pay-per-use model.

<P>
Now let us take a step back and summarize a few important developments:

<P>

<OL>
<LI>The web is a dominant and ubiquitous computing technology. It will
  replace many traditional desktop application environments and provide ubiquitous information access.
</LI>
<LI>Web applications have to cope with increasing demand and scale
  to larger user bases. Applications that incorporate features such
  as collaboration and web real-time interaction are facing new challenges as
  compared to traditional web applications. 
</LI>
<LI>Multi-core and multiprocessor architectures will dominate the processor
  landscape. At least for the next decades, performance gains of processors will mostly be
  attributed to increasing numbers of cores or processors and not to increased
  clock cycle frequencies.
</LI>
<LI>Large, scalable systems can only be designed when taking into
  account the essence of distributed and concurrent systems. Appropriate
  programming languages, frameworks and libraries are necessary to implement
  such systems.
</LI>
</OL>

<P>
In this thesis, we will bring together these individual developments to have a
comprehensive analysis of a particular challenge: 
How can we tackle concurrency when programming scalable web architectures?