Bio-medical Ontologies Maintenance and Change Management

100 L. Stanescu, D. Dan Burdescu, and M. Brezovan
For a usual implementation, the calculation of quadratic distance is much more
complex than calculation of distances based on Minkowski form, because it is
calculated the similarity between all the elements.
The complexity of the method is O(m 2 × n) where m represents the number of
colors resulted from the quantization process and n represents the number of images
in the database.
3.6.4 Evaluation of the Retrieval Efficiency
The scope of the indexing operations and similarity comparing is to obtain a good
efficiency for the retrieval operation. The performance of the information retrieval
operation is measured normally with three parameters [86]: speed, recall and precision.
These three parameters are determined by the indexing schema and the
method used for similarity comparing.
The meaning of the speed parameter is obvious. The performance is higher as
the speed is higher.
The recall and precision parameters are used together to measure the efficiency
of the retrieval process [36, 84].
The recall parameter measures the ability of the system to find relevant information
in the database. Recall signifies the proportion of relevant images in the
database that are retrieved in response to a query [41, 84]. To test the system performance,
an expert has to determine the number of relevant articles in the database,
for each query that is tested. The performance is higher as the value of this
parameter is higher.
The precision parameter measures the accuracy of the retrieval operation. Precision
is the proportion of the retrieved images that are relevant to the query [41,
84]. If it is taken into consideration only this parameter, the performance of the
retrieval operation is higher as the value of this parameter is higher.
Let consider A, the collection of relevant articles and B the collection of retrieved
articles. The a, b, c and d are defined next (figure 3.6):
• a = relevant retrieved articles
• b = not relevant retrieved articles
• c = relevant articles that are not retrieved
• d = not relevant articles that are not retrieved
a c
b
B
d
Fig. 3.6. A – relevant articles collection; B – retrieved articles collection
A