Information Technology Reference
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However the influence of the age will not be the same for all document types:
some type of analysis may be valid for several months meanwhile others are valid
for years.
Hence we propose to modify the pertinence of the document depending on a
established age threshold in months. If the document is younger than the threshold
we want the time pertinence to be high (value grater than 0.7). If it is older, we want
the time pertinence to decrease and give a low value.
To fulfill this restriction we propose the next definition.
Definition 34.
Been
D
a document and
A
the age of the it (express in months), we
calculate the
Time pertinence of document D
as
log
B
(
A
)
e
−
P
T
(
D
)=
(23.1)
e
where B
∈
]
1
,
+
∞
]
is a parameter defining the decreasing strength.
Figure 23.4 shows the behavior of the function according to the value
B
. Let note
that the value of
B
is the point where the function has the first value under 0.7 (high
pertinence).
Fig. 23.4
Behavior of the time pertinence
P
T
(
X
)
, according to different values of
B
