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does not need to establish an account to use the 
directories and no passwords are required. Users guides 
to the directories are available (Shipe, 1993; Shipe and 
Bailey, 1993), but no training is necessary to use the 
system to get information on Earth and space science data 
sets as well as information on selected data information 
systems, spacecraft, sensors, and data gathering projects 
or campaigns. 
Figure 2 is a picture of the current and potential new 
nodes of the IDN. Two types of nodes are shown. The 
coordinating nodes have completely identical databases at 
each location (U.S., Italy, and Japan). They are open to 
use by the general community and are particularly 
intended for access by users in the continental vicinity in 
which they are located (i.e., America, Europe, and Asia). 
Access information for these nodes is supplied in Table 1 
fora variety of mechanisms. The other cooperating 
nodes share information with the coordinating nodes but 
have databases which may be a subset of those of the 
coordinating nodes. In some cases, such as in Canada, 
the cooperating node maintains a complete copy of the 
database. Cooperating nodes contribute information to 
the overall network but may only be used by a small 
group for local data management and information 
purposes. Many of these types of nodes exist now and 
more are being considered for the future as indicated by 
the dashed lines to some of these nodes. Access 
information for both coordinating and cooperating nodes 
[J] COORDINATING NODE 
C COOPERATING NODE 
Wow FUTURE COOPERATING NODE 
  
  
  
     
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is summarized in the brochure entitled "International 
Directory Network". These brochures are available from 
the authors. 
The glue which binds the IDN is a standard method of 
describing dataset information called the Directory 
Interchange Format (DIF). All dataset information 
exchanged among the nodes is transferred in this form. 
Contributions of information on datasets by the general 
community are encouraged. Creation of a DIF file 
describing a dataset is a relatively simple process and, 
once this file is created, it can be automatically loaded 
into the directory databases and shared with the other 
directory nodes. Thus, the information is quickly spread 
throughout the world. The Directory Interchange Format 
Manual (1993) is the definitive document for this format. 
The IDN provides more than just dataset information, 
however. When the user accesses a particular dataset 
description there is sometimes an indication that an 
automatic connection is available to another information 
system which has more detailed information about this 
dataset. Whereas directories just have brief, overview 
information about datasets, the other information systems 
may offer more complete information about the dataset 
such as calibration information, sensor characteristics, 
detailed usage information, etc. These types of 
information systems are classified as "guide" systems. 
Still others contain details about the elements of the 
    
  
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Figure 2: The International Directory Network 
237