RE: [Repast-developer] Context - Topology vs. Model - Graph

[Tom H. <th...@sr...>]

I'm feel like the Topology needs to have an internal type as well as the
context.  Here's why:

You have a Context called Workplace.  In this Context, there is a
Reports-To topology,
a gets-advice-from topology and a friends topology. (Apologies to
Krackhardt).  But they all fall under the Context called workplace.

I do like the comparison with Servlets, etc.  This is very much how I
was thinking of the Context stuff.  If we think of Context at the
SimModel level, though, I think that we need to have the ability for
nested Contexts.  Using the scenario above, I could see a situation
where someone interacts in a WorkPlaceContext as well as a
FamilyContext.  These would need to be nested inside GeneralContext at
the model level.  I actually think that this is a very good idea.  It
would fall into line with many of the ideas David has about situation
theory.

Let me know what you think.

-Tom

-----Original Message-----
From: rep...@li...
[mailto:rep...@li...] On Behalf Of Mark
R. Diggory
Sent: Sunday, July 20, 2003 10:10 AM
To: repast-developer
Subject: [Repast-developer] Context - Topology vs. Model - Graph


I've been trying to get this concept of mapping between Topologies, 
Graphs and Spaces a little clearer in my own head. Basically I think it 
boils down to the following:


Context:
Simply a Map of existing Topologies based on key "type". Adding a Agent 
to the Context actually adds it to all the Topologies that are in that 
Context, removing does the opposite.

Topology:
DiscreteSpace, Graph or Other Object that encapsulates the relationships

between a Set of Objects.


1.) I'm concerned about Topologies having "type" defined internally 
within them. theres always room for errors where the type in the 
Topology may be able to get out of sync with the type it is mapped to in

the context. I recommend removing or internalizing/finalizing this and 
only focusing on mapping by the key/value pairs of the Context.

2.) I'm starting to think that a Generic Context could be written into 
SimModels (or SimModelImpl/SimpleModel) in such a way that we begin to 
define "Context" in terms of its "generic" definition and the way it is 
usually applied in the programming community.

For example, in the JSP/Servlet API, Context refers to attribute 
"mappings" of various "scopes". ServletContext, SessionContext, 
RequestContext are various scopes where attribute mappings can occur, 
each has a certain scope of longevity (Servlet the longest -- request 
the shortest). There are also usage of Contexts in other Applications; 
JNDI/LDAP, Jelly, JXPath, Jaxen, Xalan, Saxon to name a few. Mostly 
oriented to Webapplications, I believe this is where the design pattern 
originated. In all cases the concept of a "Context" is approximately the

same. It keeps a set of mapped attributes (or topologies in our case) in

scope for a specific hierarchy of events/objects that are being
processed.

It may be possible to look at a "basic" Repast model to begin to see 
this applications power:


Global Context
(1.SimModel)
    |
Spatial Topology --------->  Localized Context
(2.Space, Graph...)          (3. Agent)
                                 |
                              Game Topology -----> Ultimate Decision
                              (4. a set of possible Decisions)


This sort of structure would allow one not only to "hot swap" various 
Spatial and Graph Topologies at level 2, but to also "hot swap" various 
Gaming strategies applied at the "scope" of each Agent. A Game then 
becomes a topology of related "decisions" that an Agent may decide 
between when being processed, different decision topologies would have 
different content and structure thats independent of the actual 
"Decisions".

I've been playing around with "Functors" on another project. Functors 
are basically Objects that can perform a "function" on a set of objects.

If "Decisions" were "Functors" in a RePast model then they could 
encapsulate a coded "action" that is to be performed on an Agent in a 
Topology of that model. In a generic "Gaming" framework, the user would 
only need to write "Decisions" that would be performed. The framework 
could provide generic API's upon which these Decisions would be coded.

-Mark




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