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

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further qualify relationships and relationship types.
Each relationship in the dictionary has a single internal number that you can use in place of the
relationship’s entity list. Similarly, each relationship type has a single internal number that you can use
in place of the entity type list. A single internal number therefore, replaces up to six names in a
relationship or relationship type.
Restructuring the Dictionary
Whenever you modify the dictionary structure, that is, whenever you add, delete, or modify any entity
types, relationship types, relationship classes, attributes, entity type/attribute pairs, or relationship type/
attribute pairs, System Dictionary requires that you use a process called restructuring to incorporate those
changes into the working dictionary. Restructuring is essentially a compilation of the dictionary structure
into a form easily accessible by the dictionary intrinsics, and reformatting any dictionary occurrences that
are affected by the structure changes.
NOTE The entire dictionary structure is not necessarily recompiled. Only those definitions
that are affected by the changes made to the dictionary structure will be involved in
the restructuring process.
Many structure changes may be incorporated into a single restructuring, thereby increasing the overall
efficiency of the restructuring operation. This grouping of structure changes is controlled by allowing
structure changes to be made only while the dictionary is open in the exclusive customization mode.
You may make as many structure changes as desired during a session open in this mode. However, the
only operations allowed in this mode are:
• Structure changes
• Retrieval of structure information
• Limited retrieval of security information
You cannot perform any operations involving dictionary occurrences while the dictionary is open in
exclusive customization mode. When you close the dictionary, any restructuring required is performed
prior to the actual termination of access. Opening the dictionary with this special mode implies exclusive
access to the dictionary and is limited to the DA scope or scopes with extend capability.
A dictionary structure change can affect occurrences in the dictionary in several ways. For example,
deleting an entity type causes any existing occurrences of that type to be deleted and adding an attribute
to an existing entity type causes all occurrences of that type to be modified. This restructuring of the
dictionary and reformatting of occurrences is completely transparent to you. The different types of
changes are handled in the following manner:
• Adding an attribute to an entity or relationship type causes all occurrences of that type to receive a de-
faulted attribute value for the new attribute.
• Deleting an alias or variable length attribute causes all attribute values associated with the attribute
to be deleted.
• Deleting an attribute from an entity or relationship type causes that attribute to be removed from the
attribute list of the entity or relationship type and causes the attribute value of the attribute to be re-
moved from all occurrences of that type.
• Changing the size of an attribute causes the attribute value to be adjusted in size for all occurrences of
entity and relationship types that have that attribute.
• Deleting a relationship class causes any relationship types that use that class to be deleted.
• Deleting an entity type causes any relationship types that include that entity type to be deleted.