When you describe the Update function:
- I take it that c is a child table which you haven't described. Could this
be a library of geometries??
- Set c.the_geom = ? (Parent geometry??)
Bob
----- Original Message -----
From: "Sufficool, Stanley" <[EMAIL PROTECTED]>
To: "PostGIS Users Discussion" <[email protected]>
Sent: Monday, June 02, 2008 10:06 AM
Subject: RE: [postgis-users] Creating a Flow Diagram
Comments below
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On
Behalf Of Bob Pawley
Sent: Monday, June 02, 2008 9:30 AM
To: PostGIS Users Discussion
Subject: [postgis-users] Creating a Flow Diagram
Hi Stanley
I'm still in the primary learning stage with Postgis.
I would appreciate you critiquing my thoughts.
With the two tables - entity and entity_relationship - the idea is to
establish a parent geometry (perhaps a point known to be
within established
boundries) and establish the position of child entities ( in
my case,
process graphics) in relationship to the parent.
That is correct. The entitity table would contain 2d/3d Polygons of your
diagram entities. Points in this table would not work due to st_centroid
in the would-be trigger function. A slight modification would fix this.
Furthermore, you seem to indicate that any entity can be both
a parent
and/or a child to another entity.
Yes, this allows for one to many relations of parent to child (1-->2 &&
1-->3) and for network diagrams
You also indicate that the placement of the child entity can
be established
in relation to the relative geometric sizes of the entities.
Yes, examples:
For a parent entity (1) with a child (2) placed to the right of the
parent, you would have entity_relation (1,2,1,0,0)
For a parent entity (1) with a child (2) placed to the top of the
parent, you would have entity_relation (1,2,0,1,0)
For a parent entity (1) with a child (2) placed to the left of the
parent, you would have entity_relation (1,2,-1,0,0)
*If anyone actually produces a 3d diagram using the ratio_z, this would
be a first in my book and would be very interesting to see.
Have I been somewhat correct so far?
Bob
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