The qualifier system is a subtle modification of the item and item type relationship, which is most easily understood using an example.

We have already looked at the concept of 'sub-groups' in which we can create a second-level hierarchical relationship between lookup items (e.g. Protected Characteristics, containing groups for Race, Religion etc.) but here, we create the relationship at the very basic level.

Sub-groups are not suitable for when the relationship needs to be created in use within the application, or where a lookup item might be in several groups. For example: an individual could be both an Author and an Editor of the same item in the catalogue, or could be an Author or an Editor on other items, separately. We just do not know beforehand.

This is where the Qualifiers system comes in. First we create a Lookup Group to contain the Lookup Items (in our example case, 'Contributors'.

Next, we create a second group called 'Contributor Types' and set its Focus to 'Qualifier', and the field now labelled 'Qualifies:' to the group 'Contributors', which we just created.

No further work is required within the Manage Lookup dialog other than creating a series of qualifier Items within this group (Author, Illustrator, Editor etc.), and a series of conventional Items (e.g. names of authors) within the associated type. The rest of the work needs to be done as we are creating Items - we add Contributors to the item as normal, but Pergamon will detect that it is also associated to a Qualifier group and automatically provide the means to select a qualifier value.

It would be perfectly possible to therefore have two records, each containing:

• Item Title: I, Robot
  
• Contributor: Isaac Asimov
  
• Qualifier: Author

• Item Title: Nebula Award Stories (8)
  
• Contributors: Isaac Asimov
  
• Qualifier: Editor

The actual use of the qualifier is made when attaching 'Isaac Asimov' (the same lookup item) to a catalogue record using the Manage Index Items dialog.

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