Commentary on 0518_Scribe.pdf r208:

"Design Space":
---------------

The term "design space" refers to a set of possible design
alternatives.  A design space may be characterized formally or
informally. Some ways of characterizing a design space formally
include the Pareto Front (which requires formalizing the metric or
objective space) or a morphological analysis (which formalizes the
design decisions).

What is the relationship between designs in a design space? Are they
totally ordered, like the integers? Usually not. It is more common
that the designs in a design space are partially ordered, and that
there is no distinguished supreme design in that ordering.

In a total order, any two elements can be compared and the result of
that comparison is either <, >, or =. In a partial order a comparison
may result in <, >, =, or ?: i.e., there may be pairs of unequal
elements for which we cannot determine which is better than the other.

For example, in Lab 1 we looked at four designs for a simple
calculator program. None of these designs is strictly better than the
others. They all represent different trade-offs.


Partial Orders / Hasse Diagrams
-------------------------------

Drop the heading "On Hasse Diagrams" and drop the blurb under it.
Replace with something along these lines:

The following Hasse diagram shows the set of all subsets of the set
{x, y, z}, ordered by inclusion (i.e., the subset relation).  This is
an example partial order [from the Wikipedia page on partial orders].
For example, we see that the set {x, y} includes (is "greater than")
the set {x}.  However, the sets {x, y} and {x, z} do not include each
other and are not equal: they are "incomparable". 

The partial order depicted in this Hasse diagram has a distinguished
greatest element, namely the set {x, y, z}. It also has a
distinguished least element, namely the empty set.

Design spaces rarely have distinguished top and bottom elements: there
is usually no single best nor worst design. Imagine this Hasse diagram
with the top and bottom removed: that's what most design spaces look
like. 


"What are the axes on this graph?" This question is wrong. The
question I asked in class was "what are the axes on the graph that
Bill Moggridge uses to contrast different design disciplines?" We
studied that graph on a previous day. The point of the question is to
remind people about Bill Moggridge, who gives the listing of Core
Skills of a Designer that we discuss next.


Note when answers are given by the class. For example, you have class
answers to both the core skills and idea generation questions.


I mispoke in class: it was Alan Turing who like to run long distances,
not Alan Kay. Alan Kay has his own shower in the basement of Xerox
PARC.


The "weak form" and "strong form" refer to generating new ideas by
changing the technology.


Relational column stores are not just trendy: they do some things
better than relational row stores (and some things worse). Look this
up and correct the notes.


I particularly like your question #3.


Question #4 should be rephrased: say "behind" the Pareto front instead
of "above". In the example Pareto front we saw "behind = above"
because we're trying to minimize both objectives. If we were trying to
maximize both objectives then "behind" would be "below". 

Perhaps change question #4 to say "what does it mean if a design is
dominated? (in the context of a Pareto Front)". There exists at least
one other design that is strictly better than it on every criteria
under consideration.