HP 3000 Manuals

Getting Started with HP IMAGE/SQL

Defining the Data Sets 

Once you have added the necessary key attributes that support the
relationships, you have completed the majority of the work in designing
the TurboIMAGE/XL database.  Before the database can be completed, paths,
a distinction of TurboIMAGE/XL, must be defined.

Paths are fixed relationships between entities that provide fast access
to data and define referential integrity.  Relationships are defined by
designating entities as Master Data Sets and Detail Data Sets, and then
linking them with paths.

Note that the Composers and Albums entities each have only one key item,
whereas the other entities have more than one.  A Master set, by
definition, has one key item, whereas a Detail set may have up to
sixteen.  A Detail set contains one or more entries linked to a Master
entry where the key values agree.

For example, Album Code 0019 is assigned to the Beethoven's hits album
mentioned before.  This information is in the Albums entity.  There are
two selections on the album:

   *   Beethoven's Fifth Symphony
   *   Beethoven's Ninth Symphony

These entries are in the Selections entity.

If a query is made for Album Code 0019 against Albums, one entry is
returned.  There should only ever be one entry returned.  If the same
Album Code is requested from Selections, two entries are returned, equal
to the number of selections on the album.

Albums, then, is a candidate for being a Master data set and Selections
will be a Detail data set.  Selections also has a second key, Composer
Name, a condition that forces it to be a Detail set.

One other distinction within TurboIMAGE/XL before continuing with our
design:  Master sets are either Manual Masters or Automatic Masters.
Each has a single key, but Automatic Masters can contain no other
attributes.  Manual Masters can have other attributes per entry.

Also, Automatic Master key values are added and deleted automatically;
their function is to provide fast access paths to data.  Manual Master
key values and their associated attributes must be added and deleted
explicitly, thereby supporting the referential integrity concept
discussed earlier and providing fast access to data.

The TurboIMAGE/XL database designed so far is shown in Figure 4-1 .


          Figure 4-1.  Database Design 

Composers and Albums are Manual Master data sets, Selections and Log are
Detail data sets.  Because Selection Name is a key value in both
Selections and Log, a supporting Automatic Master was created to supply
the keyed access to these two entities.

Before you see the schema to create this database, a final design
consideration must be addressed:  security.

MPE/iX 5.0 Documentation