Each query has a single output component, zero or more valid-time
selection components (one per such operator), and zero or more
non-temporal selection-based components (one per such operator). The
taxonomy is summarized in Figure . There, the names
introduced in the taxonomy are used along with punctuation in order to
name a category.
To exemplify the use of Figure for naming categories,
consider the query ``When was ED manager of the Toy
department?'' Using the schema of Figure
(this schema
will be used in the remainder of the document unless explicitly stated
otherwise), this query is in the category shown next (with no
valid-time selection).
It may be observed that the taxonomy gives rise to a large number of categories. For example, assuming a single non-temporal operator and no valid-time operators, there are 38×8 = 304 categories. Adding a single valid-time operator while assuming orthogonality yields 8208 categories!
As a result, it becomes necessary to create classes of categories which then may be used for classifying the queries.
One approach would be to name a class of categories of queries, by simply replacing one or more of the entries with the Kleene star (``*''), e.g.,
The above query category would be in this class. In the next section, we define the classes to be used in the test suite.