Valerie Wiersma
INFORMATION_ARCHITECTURE
INFORMATION_ARCHITECTURE_274_STUDY
So, Alexander famously advocated on-site improvisation by concerned, empowered users,
as a powerful way to form very workable large-scale initial solutions, maximizing the utility
of a design, and minimizing the design rework.The desire to empower users of architecture
was, in fact, what led Alexander to undertake a pattern language project for architecture in
the first place.== Design problems in a context ==
An important aspect of design patterns is to identify and document the key ideas that make
a good system different from a poor system (that may be a house, a computer program or an
object of daily use), and to assist in the design of future systems.The idea expressed in a
pattern should be general enough to be applied in very different systems within its context,
but still specific enough to give constructive guidance.The range of situations in which the
problems and solutions addressed in a pattern apply is called its context.An important part
in each pattern is to describe this context.Examples can further illustrate how the pattern
applies to very different situation.For instance, Alexander's pattern "A PLACE TO WAIT"
addresses bus stops in the same way as waiting rooms in a surgery, while still proposing
helpful and constructive solutions.The "Gang-of-Four" book Design Patterns by Gamma et
al.proposes solutions that are independent of the programming language, and the
program's application domain.Still, the problems and solutions described in a pattern can
vary in their level of abstraction and generality on the one side, and specificity on the other
side.In the end this depends on the author's preferences.However, even a very abstract
pattern will usually contain examples that are, by nature, absolutely concrete and
specific.Patterns can also vary in how far they are proven in the real world.Alexander gives
each pattern a rating by zero, one or two stars, indicating how well they are proven in realworld examples.It is generally claimed that all patterns need at least some existing realworld examples.It is, however, conceivable to document yet unimplemented ideas in a
pattern-like format.The patterns in Alexander's book also vary in their level of scale – some
describing how to build a town or neighbourhood, others dealing with individual buildings
and the interior of rooms.Alexander sees the low-scale artifacts as constructive elements of
the large-scale world, so they can be connected to a hierarchic network.=== Balancing of
forces ===
A pattern must characterize the problems that it is meant to solve, the context or situation
where these problems arise, and the conditions under which the proposed solutions can be
recommended.Often these problems arise from a conflict of different interests or "forces".A
pattern emerges as a dialogue that will then help to balance the forces and finally make a
decision.For instance, there could be a pattern suggesting a wireless telephone.The forces
would be the need to communicate, and the need to get other things done at the same time
(cooking, inspecting the bookshelf).A very specific pattern would be just "WIRELESS
TELEPHONE".More general patterns would be "WIRELESS DEVICE" or "SECONDARY
ACTIVITY", suggesting that a secondary activity (such as talking on the phone, or inspecting
the pockets of your jeans) should not interfere with other activities.Though quite unspecific
in its context, the forces in the "SECONDARY ACTIVITY" pattern are very similar to those in
"WIRELESS TELEPHONE".Thus, the competing forces can be seen as part of the essence of a
design concept expressed in a pattern.=== Patterns contain their own rationale ===
Usually a pattern contains a rationale referring to some given values.For Christopher
Alexander, it is most important to think about the people who will come in contact with a
piece of architecture.One of his key values is making these people feel more alive.He talks
about the "quality without a name" (QWAN).More generally, we could say that a good
system should be accepted, welcomed and happily embraced as an enrichment of daily life
by those who are meant to use it, or – even better – by all people it affects.For instance,
when discussing a street café, Alexander discusses the possible desires of a guest, but also
mentions people who just walk by.The same thinking can be applied to technical devices
such as telephones and cars, to social structures like a team working on a project, or to the
user interface of a computer program.The qualities of a software system, for instance, could
be rated by observing whether users spend their time enjoying or struggling with the
system.By focusing on the impacts on human life, we can identify patterns that are
independent from changing technology, and thus find "timeless quality" (Alexander).==
Generic structure and layout ==
Usually the author of a pattern language or collection chooses a generic structure for all the
patterns it contains, breaking each into generic sections like context, problem statement,
solution etc.Christopher Alexander's patterns, for instance, each consist of a short name, a
rating (up to two '*' symbols), a sensitizing picture, the context description, the problem
statement, a longer part of text with examples and explanations, a solution statement, a
sketch and further references.This structure and layout is sometimes referred to as the
"Alexandrian form".Alexander uses a special text layout to mark the different sections of his
patterns.For instance, the problem statement and the solution statement are printed in bold
font, the latter is always preceded by the "Therefore:" keyword.