HP System Dictionary/XL General Reference Manual Vol 1 (32256-90004)

4- 41

• Every status change a version has undergone since its creation, and the date and time of each change.

• Every version that currently has a particular status.

Accessing Versions

Like domains, versions are part of the access path to a particular dictionary. Therefore, you must specify a

version each time System Dictionary is open in a mode that allows access to versions. Note that you can

specify the version by either version name or version status. As with domains, you can access only one

version at a time, and you may switch versions while the dictionary is open. It is possible, through the

System Dictionary intrinsics, to establish multiple access paths to the same dictionary, specifying a

different version in each access, but you can specify only one version per dictionary access path. You can

reference the version currently in Production status, and the versions most recently assigned to Test and

Archival statuses without knowing their names, by specifying their status.

Linking Versions

Before you can link occurrences in a local domain version to occurrences in a common domain version

(linking is discussed below), the local domain version must be linked to the common domain version. Once

you link the versions, you can only link occurrences contained in the local domain version to occurrences in

the common domain version it is linked to. For example, if you link version MFG1 of local domain OPS to

common domain version A, then you can only link version MFG1 occurrences to common domain version A

occurrences. Note that the linked versions are not required to have the same name.

You can move the link from a local domain version to a different version in the common domain. Before

you can move the link, however, the new common domain version must contain a corresponding occurrence

for each occurrence in the existing common domain version that is linked from an occurrence in the

speciﬁed local domain version. For example, the local domain version MFG1 contains entities LE1 and

LE2 of type RECORD, which are linked to entities CE1 and CE2 of type RECORD in common domain

version A. Before you can move the links from common domain version A to common domain version B,

common domain version B must contain entities CE1 and CE2 of type RECORD.

Deleting Versions

You can remove a version and the set of occurrences it contains from the dictionary as a unit. As with

domains, this feature allows you to see a version as a storage space for temporary deﬁnitions, which you

may delete all at once by simply deleting the version. Note, however, that you cannot delete any version

having the status of Production. You would have to change the status of the version from Production to

either Test or Archival to delete it. Note also, that you cannot delete a version in the common domain

until you delete all links to occurrences it contains, and you delete all links to it from local domain

versions.

Linking Occurrences

One of the major functions of a data dictionary is to ensure the standardization and integrity of the

deﬁnitions used in an information system. However, you can use the domain feature of System Dictionary

to unintentionally defeat this standardization. You can create "non-standard" dictionaries by creating

identical occurrences in different domains, or by creating occurrences in different domains which, though

not identical, should be. For example, an entity named LAST-NAME of type ELEMENT exists in four local

domains. Each entity was created by a different user, and has a different value for one of its attributes,

BYTE-LENGTH. These different values mean that there is possibly no standard length for last names

described in the dictionary. If these differences are due to application requirements, the domain feature

serves a useful purpose, but if they are unnecessary, the domain feature is allowing non-standardization,

and its use should be looked at carefully.