Tom wrote:

> Hi Alan / Alain

> I don't seem to have been very successful in steering away from
philosophy towards the empiricism of measurement.

> As you guessed, I am not qualified to expound the philosophy of
space, in relativistic,  quantum or any other models.  As Alain said, I
was being rhetorical, bringing in the aether as an absurdity to bounce
us back into "How SS can ACTUALLY help to look at the way a building
is used."

> However, I think you agreed that what you ACTUALLY measure are
relationships between objects or the physical limits of activity
(although I am still a little puzzled by the form of words).  In fact the
Ordinance Survey often measure the 'Spaces between' physical
surfaces for us, in making the maps we work from.

Tom - go back and re-read my description of representation maps. The
relations we ACTUALLY measure are between elements of space, not really
objects (although one can also do that and it has been done). The ordnance
survey don't measure anything in the same way that we do. That is they
survey space and built form and represent it as maps, but they do not then
analyse that map in any specific way to quantify particular properties of
the morphology.

> I am suggesting that drawing the diagram of convex spaces / axial
lines is a process of mapping "spaces for . . ." onto this map of
"spaces between . . .."  It is a microcosm of the social-space mapping
Alan mentioned before, because the axial lines / convex spaces mark
the physical limits of co-presence (where co-presence means that
people at any two locations can see each other and move to meet
each other) ie. they are "spaces for . . ."

Tom, at the risk of getting slightly pedantic, although one interpretation
of the empirical success of convex and axial maps in explaining social
phenomena is to do with visual co-presence, it is not obvious that this is
the reason why the analysis is explanatory. So although I go along with your
point and often use this 'explanation' in describing the methodology to
people to try and help them understand, to be quite honest I think that it
is only part of the story.

> And this is important in finding "How SS can ACTUALLY help to look at
the way a building is used."  To mark out systems of co-presence
encourages us to look for causal relations between human interaction
and higher level social phenomena.  Because co-presence includes
co-visibility it raises questions related to human vision, such as the
cognitive complexity of routes.  Because it includes co-accessibility,
we should ask about the physical pre-requisites of human movement,
such as route density.

> The danger I see in describing SS in abstract terms of 'space as
space' is that it becomes detached from this grounding in reality.  It is
no longer obvious that the measurements relate to the affordance of
the sort of activities which we are designing for.  Of course the data
becomes more abstract as you process it with mathematical tools of
topology and graph theory, but this should be processing information
about particular, specified phenomena.

I wonder whether you are actually hoping for a relatively 'mechanistic'
causal explanation. I am suggesting that although that may well be the case,
the evidence so far doesn't let us distinguish between a causal and a more
abstract explanation. To give an example - about 70% of variance in observed
aggregate movement rates in urban space can be 'explained' by software
agents with 'vision' taking their next step at random from their visual
field, and re-evaluating every three steps. These 'agents' have no
psychology and are effectively randomly sampling the spatial environment.
What they suggest is that a good proportion of the observed regularity in
human behaviour may be no more than mathematical necessity - no need to
invoke psychology or cognition at this level.

> Doubtless the axial line gathers up a whole lot of different affordances,
of varying importance in different situations.  But we can't see them, so
we can't relate it to our work.  It looks like a mysterious object which
has been FOUND in the world, instead of an abstract measurement
OF the world.  Perhaps it is time to 'unpack' the axial line and have a
look at the social / spatial ideas inside it, which  can ACTUALLY help
to look at the way a building is used.

Perhaps.

Alan