In this example, we have introduced the concept of units nested within a product. A slightly 
different method, which is used in many real-time and archival applications, creates subsets 
of data within a product. That is to say, all data objects of a specific type are collected 
together into units which may be further aggregated into a product. 
Additional objects and units may be added to the product as necessary. 
Identification information is comprised of catalog information and production information. 
The former includes such items as data type, start/end time, instrument identification, etc. 
The latter can include the time and location of the creation of the product, the 
representation of binary values, the machine and operating system used to create the 
product, etc. Global identification information applies to the whole product. The instance 
identification information is applied to a particular instance and thus can, in general, change 
from instance to instance. 
STANDARD FORMATTED DATA UNITS 
The Standard Formatted Data Unit (SFDU) concept provides the protocols needed to 
enable the access and understanding of information on a global basis by providing: 
1) a means for aggregating instances of application data, ancillary data and metadata 
(data about data) into data products, 
2) a means for globally defining and identifying data products, and 
3) a means for administering the data product definitions to ensure their accessibility 
and understanding. 
The SFDU methodology promotes documentation rigor through the administrative services