Multicriteria Information Retrieval in Textual Corpora - Geographical Information Retrieval in Textual Corpora - page 67

Figure3.3(a))andanintervaloftimewiththeTF“inearlyJanuary2001”(see TF #9 ,
Figure 3.3(b)).

a) b)

Figure 3.3. Example of an application of tiling: a) spatial features on a
communal administrative tiling and b) temporal features on a monthly
calendar tiling - illustration taken and then adapted from [PAL 10d, PAL 11]

Standardization by tiling will then be performed in two steps: the choice of the
segmentation for each dimension and then the representation of the information of
each first-level index in this tile-based grid. Thus, the spatial information needs a
regular or administrative tiling (commune, county, etc.) of the zone covered by the
document repository and a calculation of intersections of the SFs of the index and of
this tiling. Similarly, temporal standardization needs a regular or calendar tiling (day,
week,month,etc.)oftheperiodcoveredbythedocumentrepositoryandacalculation
of intersections of the TFs of the index and of this tiling.

Figure 3.3(a) illustrates the communal administrative tiling of the zone. The SF
“near Bayonne” (SF #5 ) is in intersection with seven tiles (communes surrounding
Bayonne).Similarly,Figure3.3(b)illustratesthemonthlycalendartilingoftheperiod.
The TF “in early January 2001” (TF #9 ) is included in the T 9 tile (month of January
2001).

The index excerpt presented in Table 3.1 illustrates the application of temporal
tiling described in Figure 3.3(b): we can find the corresponding frequencies for the
tiles T 1 , T 2 ,...,T n .For example, TF #6 is in intersection with four tiles (T 2 , T 3 , T 4 ,
T 5 ); the binary frequency relative to each of these tiles will be increased by 1. As for
the tile T 3 , it is in intersection with two TFs (TF #2 and TF #6 ); consequently, it will
haveastandardweightof2.Theproportionalfrequencytakesintoaccountthesurface
ofcoveragecorrespondingtotherepresentationofafeatureandtothatofatile.Italso
takes into account the scale of the feature with respect to that of the tile. For example,
such a calculation will determine a proportional frequency of 1.08 for the application
of TF #2 and TF #6 on the tile T 3 .