Criteria

Three criteria for an appropriate taxonomy of queries are suggested.

• The taxonomy should be schema and instance independent. This criterion helps ensure that the taxonomy will persist when the database schema evolves as new versions of the test suite appear. Ideally, this will allow for an incremental mode of work, where only new queries need to be categorized and existing queries do not need re-categorization.
• The taxonomy should provide extensive coverage of queries. Extensiveness is desirable to avoid holes and point to many categories of queries.
• The taxonomy should be useful when structuring the presentation of the test suite. Most importantly, it should provide sufficient structure. Thus, taxonomies that have only few categories and that map many queries to single categories are problematic. If the number of categories is excessive for presentation purposes, classes of categories may be identified with individual sections.