Context-Aware Applications - Guide to Cloud Computing for Business and Technology Managers - page 500

23.1.1 Concept of Patterns
The concept of patterns used in this topic originated from the area of real
architecture. Alexander gathered architectural knowledge and best prac-
tices regarding building structures in a pattern format. This knowledge was
obtained from years of practical experience. A pattern according to Alexander
is structured text that follows a well-defined format and captures nuggets
of advice on how to deal with recurring problems in a specific domain. It
advises the architect on how to create building architectures, defines the
important design decisions, and covers limitations to consider. Patterns can
be very generic documents, but may also include concrete measurements
and plans. Their application to a certain problem is, however, always a man-
ual task that is performed by the architect. Therefore, each application of a
pattern will result in a differently looking building, but all applications of
the pattern will share a common set of desired properties. For instance, there
are patterns describing how eating tables should be sized so that people can
move around the table freely, get seated comfortably, find enough room for
plates and food, while still being able to communicate and talk during meals
without feeling too distant from people seated across the table. While the
properties of the table are easy to enforce once concrete distances and sizes
are specified, they are extremely hard to determine theoretically or by pure
computation using a building's blueprint.
In building architecture, pattern-based descriptions of best practices and
design decisions proved especially useful, because many desirable prop-
erties of houses, public environments, cities, streets, etc., are not formally
measurable. They are perceived by humans and, thus, cannot be computed
or predicted in a formal way. Therefore, best practices and well-perceived
architectural styles capture a lot of implicit knowledge how people using
and living in buildings perceive their structure, functionality, and general
feel. Especially, the indifferent emotion that buildings trigger, such as awe,
comfort, coziness, power, cleanness, etc., are hard to measure or explain and
are also referred to as the quality without a name or the inner beauty of a building .
How certain objectives can be realized in architecture is, thus, found only
through practical experience, which is then captured by patterns. For exam-
ple, there are patterns describing how lighting in a room should be real-
ized so that people feel comfortable and positive. Architects capture their
knowledge gathered from existing buildings and feedback they received
from users in patterns describing well-perceived building design. In this
scope, each pattern describes one architectural solution for an architectural
problem. It does so in an abstract format that allows the implementation in
various ways. Architectural patterns, thus, capture the essential proper-
ties required for the successful design of a certain building area or function
while leaving large degrees of freedom to architects.
Multiple patterns are connected and interrelated resulting in a pattern
language . This concept of links between patterns is used to point to related