HP 3000 Manuals

HP System Dictionary XL Gen. Ref. Vol. 1

Domains and Versions 

One important function of a data dictionary is to maintain
standardization of the data in an information system.  As shown in the
previous chapter, System Dictionary includes this capability by providing
you with a standard set of structure definitions, but also the means to
extend them to meet your particular needs.

Similarly, System Dictionary provides you with the means for maintaining
a standard set of occurrences--the entities and relationships.  However,
though most of the occurrences in a data dictionary are meant to be
shared by all users, there are sometimes circumstances, applications, or
users that need separate sets of occurrences.

System Dictionary handles these needs by allowing multiple spaces called
domains within a single dictionary.  Domains are similar in some ways to
accounts in the MPE file system, and you can use them as separate
partitions for different applications, or as "name spaces" to separate
duplicate names used for different purposes.

Figure 4-1 shows examples of domains that could exist within a particular
configuration of System Dictionary.  The center area represents the
common domain, which is the domain provided with System Dictionary.  The
other spaces represent user-created domains, called local domains.  The
common domain and local domains are discussed further on in this chapter.


          Figure 4-1.  Dictionary Domains 

MPE/iX 5.0 Documentation