I found this explantion of 2007 Outline Codes on a blog:
http://www.projectified.com/project_server_2007/index.html
Did I hear you ask for more custom fields?
Project Server 2007 makes a major change to the way that enterprise custom
fields are handled. Instead of being tied to a limited set of fields
(Enterprise Text1, Enterprise Text2, etc.) the new system starts with
basically no custom fields and you get to add as may as you want.
The interface allows you to add a new field and that new field has several
attributes that include:
Entity (Project, Task or Resource)
Type (Cost, Date, Flag, Duration, Number and Text)
Summary rollup
Whether the field will use a Lookup Table or a formula or be 'hand entered'
Assignment 'Roll down'
If the field will display it's value or Graphical Indicators
If the field will be required to contain a value
Notice that Type does not include "Outline Code". There will no longer be an
field type called outline code. Since any field can have a hierarchical
lookup table like Project Server 2003 outline codes essentially in 2007 any
enterprise custom field can be an 'outline code'.
Lookup Tables are created independently of the fields themselves which makes
sharing them between fields much easier.
This brings us to the question you are likely asking yourself now: if there
are no enterprise outline codes then how does the OLAP cube get user defined
dimensions? Well I'm glad you asked me that...
Any Project, Resource or Task enterprise custom field can be a dimension!
(Yes ANY!) There is a Cube Configuration page that allows you to pick from
your defined custom fields and decide which ones should be OLAP Cube
dimensions. Ready for part two of that? Any Project, Resource or Task
enterprise Cost, Number or Duration field can be a measure in the cube as
well. These get defined in a central page and then show up as available for
any Data Analysis view (Data Analysis is what Portfolio Analyzer views are
called in Project Server 2007).