Preparing Attribute Data For Themes; Setting Up Your Attribute Database - Autodesk 15606-011408-9330 - MAPGUIDE R6.3 SITE LIC-UPG R6 User Manual

Preparing Attribute Data for Themes

As mentioned in the previous sections, you can use the data in a linked
attribute table as the basis for themes. Themes draw the map features on a
layer according to particular values. For example, on a map layer that
contains cities, you could use different symbols to represent cities that fall
within different population ranges. Themes also help to differentiate features
in a layer. For example, on a roads layer, you could draw interstate highways
differently from city streets, even though they're on the same layer.
When setting up your attribute data, you should consider whether you will
be creating themes, and whether the data in the table lends itself easily to
this task. For example, for a roads layer, do you already have a column that
contains the text "Interstate" or "City Street" for each feature in the table? If
so, it will be very simple to specify this column as the theme column and
specify that if the column contains "Interstate," the feature will be drawn as
a thick yellow line, and if the column contains "City Street," the features will
be drawn as a thin black line. However, if you want your roads to be drawn
in such a way as to show how heavy the traffic is, a column indicating
whether it's an interstate highway or city street will not be useful—you will
need a column that indicates how much traffic each road has. You can then
use this third column to specify how the roads are drawn to show traffic.
For example, you might create four theme categories: fewer than 200 cars per
month, between 201 and 5,000, between 5,001 and 10,000, and greater than
10,000. You can then specify the display attributes separately for each of
these categories, so that roads with the lightest traffic are drawn in thin black
lines and roads with heaviest traffic are drawn in thick red lines, and so on.
If you are using point or text data, you need to consider which symbols you
will want to use for each theme category. For more information, see
"Working with Symbols" on page 109.

Setting Up Your Attribute Database

You need to take the following points into consideration when setting up
your attribute database:
Before Autodesk MapGuide can use your databases, you must set them up


and configure them as OLE DB data sources or Autodesk DWG data
sources. For more information, see "Setting Up Your Data Sources" on
page 78.
You can limit users' access to data sources by setting up passwords for users


or for groups or by assigning access keys to the resource. For more infor-
mation, see "Managing Server Security" on page 80.
Working with Attribute Data
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