A Pattern Language

[Ravi Pandya <ravi>]

The book A Pattern Language, from which I quoted the section on
circulation patterns, is itself a finely crafted hypertext. It
describes a language of interconnected patterns for describing the
process of building and planning.

"The elements of this language are entities called patterns. Each
pattern describes a problem which occurs over and over again in our
environment, and then describes the core of the solution to that
problem.

"For convenience and clarity, each pattern has the same format. First,
there is a picture, which shows an archetypal example of that pattern.
Second, after the picture, each pattern has an introductory paragraph,
which sets the context for the pattern, by explaining how it helps to
complete certain larger patterns. After there is a headline, in bold
type. This headline gives the essence of the problem in one or two
sentences. After the headline comes the body of the problem. It
describes the empirical background of the pattern, the evidence for
its validity, the range of different ways the pattern can be
manifested in a building, and so on.  Then, again in bold type, like
the headline, is the solution - the heart of the pattern - which
describes the field of physical and social relationships which are
required to solve the stated problem, in the stated context. Then,
after the solution, there is a diagram. After the diagram there is a
paragraph which ties the pattern to all those smaller patterns in the
language, which are needed to complete this pattern."

The patterns are presented in order from the most broad to the most
local, giving the book a strong sequence from beginning to end. Each
pattern is connected to about half a dozen larger patterns, and about
the same number of smaller patterns. Furthermore, the linear sequence
is divided into three sections (Towns, Buildings, Construction). There
is an introduction at the beginning of the book, and another for each
section. Each section is divided into groups of about a half dozen
patterns, with a couple of sentences introducing the group. The linear
order of the patterns is important, so that each patterns lies next to
patterns that are of the same scope and in the same realm.

Each pattern is only a half dozen pages long, and very tightly
focused on its subject. The exposition is concise, but detailed and
thorough. Diagrams, photographs, tables, and charts are common. Along
with the effective use of typographic conventions, this makes it very
easy to read the book at different levels of detail. You can find a
few patterns you are interested in, and then skim through the related
patterns by reading just the boldface problem statement and solution,
and looking at the pictures. The references to broader and narrower
patterns are embedded in explanatory text so that you can have an
immediate idea whether it is related in a way you want to pursue.

For example, CIRCULATION REALMS begins with:

"... once you have some rough idea how many buildings you are going to
build -- BUILDING COMPLEX (95), and how high they are to be -- NUMBER
OF STORIES (96), you can work out roughly what kind of layout they
should have to make the access to them clear and comfortable. This
pattern defines the overall philosophy of layout."

and ends with:

"Treat the first entrances to the whole system of circulation realms,
the very largest ones, as gateways -- MAIN GATEWAYS (53); make the
major realms, which open off the gateways, pedestrian streets or
common land -- COMMON LAND (67), PEDESTRIAN STREET (100); then, make
minor realms with individual buildings, and courtyards, and major
indoor streets -- MAIN BUILDING (99), BUILDING THOROUGHFARE (101),
HIERARCHY OF OPEN SPACE (114), COURTYARDS WHICH LIVE (115); and mark
the entrance to these minor realms with minor entrances that still
stand out quite clearly -- FAMILY OF ENTRANCES (102), MAIN ENTRANCE
(110). Make the layout of paths consonant with PATHS AND GOALS
(120)...."

[the ellipses are in the text]

In my earlier message I quoted the boldface problem statement, and the
solution, along with a short passage from the body of the pattern. I
have a copy of the book if anyone's interested in looking at it.