of windows. Introducing so-called minimum rectangular 
frames (MRF) 
- made the uniqueness problem negligible by trans- 
ferring it to small areas and 
- together with CADLL contained scatter tables and B*- 
trees provides powerful support on searching. 
It should also be noticed that it makes a difference 
upon setting up a window whether pattern channel 
contained labels 
- come in consequence of a predetermined or 
- require to recognize from their arrangement the 
shape of a 
polygon-oriented window. Thorough solutions to the second 
procedure tend to become time consuming, but for most 
applications it is sufficient finding the corresponding 
MRF which can easily be accomplished. 
If the shape of a window is known it may at any time be 
-  enterd into any pattern channel as long as this 
does not imply collission with labels of different 
windows, 
- erased from its pattern channel without losing it 
nor any previously entered annotation on the window 
(cf. section 7), 
- Modified if it is not pattern channel contained. 
There are various means of referencing a window, namely 
by 
- name (string of characters), 
- numerical identification with respect to a user 
defined rectangular page-oriented overlay, 
- simply referring to the locus of any of its pixels 
if its shape is pattern channel contained, 
about properties (cf. section 7). 
  
inquiries