HP 3000 Manuals HP 3000 Manuals
Versions As Copies You can also think of versions as copies of the entities and relationships in a domain. In this sense, the version feature allows the creation of different versions of entities and relationships. For example, a domain called ADDRESSES contains two versions, ADRSHORT and ADRLONG. Both versions contain an entity called ZIP-CODE of type RECORD, which is described by the attribute BYTE-LENGTH. In version ADRSHORT the value of BYTE-LENGTH is 5, meaning that the entity ZIP-CODE in this version describes a 5-digit zip code. In version ADRLONG, however, the value of the attribute BYTE-LENGTH is changed to 9. The entity ZIP-CODE in version ADRLONG is therefore a different version of the entity ZIP-CODE in version ADRSHORT, and describes a 9-digit zip code. You can copy an entire set of version occurrences from one version to another. This is useful, for example, when creating a test version with all the occurrences of the current production version. Note, however, that it is not necessary for each version of a domain to contain all the entities and relationships in that domain. A version of a domain can contain more occurrences than other versions of the domain, or fewer, or may even be empty (a newly created version is always empty). With certain exceptions, the attribute values of a given entity or relationship may vary from one version to another. In fact, the main purpose of the version feature is to allow you to experiment with one version by changing attribute values or adding new definitions while other versions remain undisturbed. All versions of an occurrence use the same name and occurrence-scope associations, however, because these are defined at the domain level, as are the values for the following attributes for occurrences: * scope-owner * sensitivity * id-number (entities only) The values for all other attributes are assigned at the version level, and may be different for each version of an occurrence.