What is Patterns

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What is Patterns?

• Dr M G Srikanthan

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Introduction
All buildings are the result of applying sets of
rules. When this expertise fails to be passed on,
bad buildings and broken communities result.

• Result of this is birth of the concept of
  Patterns.
• Alexander codified best building practice by mean
  of 253 individual but related Patterns.

Christopher Alexander
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Alexanders word

• 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, in such a way that you can use this
  solution a million times over, without ever doing
  it the same way twice.
• Christopher Alexander, A Pattern Language
  Towns/Buildings/Construction, 1977, New York
  Oxford University Press

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My word

• A Pattern is a formalised instruction, so I can
  say
• If you encounter this problem, then solve it
  like that .
• But the problem must describe by contexts
• Pattern (Problem Solution )in a context
• So we can apply the concept of Patterns all most
  any where when we encounter any problem. But
  solution to the problem must be well-tried
  solutions or experts advices.

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Pattern in Real Life a strategic Pattern

• Problem with Context
• You are a student living at Waterloo, London and
  need to get to lecture at St.Patricks College
  London, in less than an hour. RMT Union announce
  strike - only limited tube services are
  available. Travelling by bus would take too long
  because of traffic jams and you dont have access
  to a bike. You only have a limited amount of
  money and need to buy lunch, pay some library
  fines and get home somehow. You could take a
  taxi, but that costs too much. The train is not
  an option. Your flatmate jogs to University of
  Westminster, but you are incredibly unfit to jog.
• Solution
• Walk to the college. Its only take 20 minutes.
  So you can reach the college before the lecture
  start.

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Pattern in Real Life preserving the pattern

• Name Punctuality on the tube strike day
• Problem How do you get to class on time?
• Solution Walk to College.
• Context Living within your financial, temporal
  and physical limits you can get to class.
• Example/known use It might take 20 minutes to
  walk to Oxford Street.
• Related Patterns Avoid Library Fine and Lunch to
  catch Black Taxi, Buy a Bike.

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Patterns in real life - summary

• Patterns also can be found in real life and the
  pattern could be a well-tried solutions to the
  real problems.
• Patterns help to
• reduce the problem solving time,
• provide reusable solutions,
• solve specific problems,
• act as templates,
• pass on knowledge from experts to novices.

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Patterns for Projects

• Instead of re-inventing the wheel for any
  project, capitalise on existing work and deploy
  it.
• Benefits
• reduced project time as one improvement will
  improve all projects
• improved quality because of through testing in a
  variety of situations
• they help through learning by example
• pass knowledge on from expert to novice
• magic words reuse
• Patterns support the modularity. So that changes
  can be made internally without affecting other
  things.

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• Qualities of a pattern There are three
  essential qualities of any true pattern
• Quality Without a Name (QWaN) Fundamentally,
  QWaN means that, when applied correctly to solve
  an applicable problem, the resulting solution
  provides a structure that can evolve over time to
  meet unanticipated future needs. Christopher
  Alexander, the originator of the concept of
  patterns, wrote extensively on this quality in
  his book 'A Timeless Way of Building.'
• Rule of Three In order for a solution to really
  be a 'pattern', there must already exist known
  uses of the solution, with results that can be
  observed. The Rule of Three, originally proposed
  by Ralph Johnson, states that, for any solution
  to be a true pattern, there must be at least
  three known instances of that solution.
• Pattern Format Patterns are documented following
  a loosely standardized format. We will discuss
  these formats in the next section. Minimally,
  though, each pattern must state its name,
  purpose, solution, the potential forces it
  resolves and the consequences of applying it.

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Do not confuse!

• Untested theories
• Solutions that have worked only once
• Applicable to every context

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How to preserve the patterns?

• Element of Components of Patterns can be used
  to document the newly identified patterns.
• Which can be called as pattern catalogue.
• Element of Patterns

• Name
• Problem
• Context
• Forces
• Solution

• Examples
• Resulting Context
• Rationale
• Related Patterns
• Known uses

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Finaly Alexanders words again ...

• They tell us what to do
• they tell us how we shall, or may, generate
  them
• and
• they tell us too, that under certain
  circumstances, we must create them.
• Each pattern is a rule that describes what you
  have to do to generate the entity that it
  defines.
• Alexander, The Timeless Way of Building, pp.
  181-182)

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Thank You