Databases Reference
In-Depth Information
to specify
associations
among the target sets. Two types of associations are
considered in AQUA. The first one is the
structural association
(S-Association).
This occurs according to a structural relationship (relative position) between two
examples. For example, if two examples are on the same page, it gives an S-
Association that objects from the target sets must be on the same page. The second
one is the
value association
(V-Association). This occurs if values of the example
objects are the same. When some associations are specified among the target sets,
only some combinations of data objects are qualified. Note that an association
serves as a kind of join condition.
Figure 10: Specification for the example scenario
Figure 10 illustrates the visual specification in AQUA to obtain the Web structure
in Section 4.1. The user has to drag-and-drop data objects from the DataBoxes
into the Canvas. We explain the operations in the chronological order. (1)First, we
open the Canvas and declare the construction of an HTML page. (2)We drag and
drop the image 'Batter Index' from the Palette into the Canvas. (3)We drag and
drop the 'ListItem' object from the Palette into the Canvas. (4)'James' in TP is
specified as an example. The default target set includes those players who appear
first in the player list on each team page. Next, 'Patrick' in TP is specified as an
'Another' object. The system uses rules to generalize the relationship between
positions of 'James' and 'Patrick,' so that the target set of this example is extended
to include all players of all teams. (5)We drag and drop the “James” from TP into
the Canvas. (6)We put a repetition mark (*) on the list item object. As a result, all
the players' names are listed in this page. Otherwise, a new page is produced for
each player. (7)'James' objects in PP and VD are specified as examples. Note that
the three target sets of 'James' objects in TP, PP, and VD have V-Association,
which specifies equality joins between their target sets. (8)We declare the
construction of a SMIL page. (9)We drag and drop the HypertextLink object from
