Introduction of the Project
This project, as a part of the Information
Storage and Retrieval course is about the visualization of
document similarity. We show the document space that represents
the similarity / dissimilarity between the documents. In our
project, we also consider query as a document and therefore
represent it in the document space. For the purpose of calculating
the distance between the documents and query, we have used Euclidean
distance and Cosine Measure. Along with these distance measure
methods, the FastMap algorithm is used to map the position of
documents and query. The visualization is represented in 2D
and 3D graphics therefore it is possible to compare how the
document space features are represented differently.
Document space is the representation
of the set of documents. There can be different ways of representing
documents, however mostly it is used to show the distance or
the similarity between different documents. When documents are
close each other in the document space this represents that
they are similar or relevant document in the set. When documents
are far apart each other in the document space this means they
are not similar or relevant each other. Therefore, to represent
documents in document space, the distances between documents
are necessary.
Document distances can be calculated
with several distance measurement methods. Mainly used methods
are vectorbased such as Euclidean measure and Cosine measure.
In vectorbased models, documents and query are represented
with their weights which correspond to the importance of the
term in the document. Here in our project, term weights are
related to the frequency of the terms in the document. Each
terms in the document will have a vector value, by which the
distace between documents will be calculated. The vector
is calculated as following formula for the first term in a document,
for example.
Vector
= ( term 1 frequency )/sqrt[( term 1 freq )^{2}+(
term 2 freq )^{2}+......+( term n freq )^{2}]

We used Euclidean Distance Measure
for calculating the document distances between two documents
or between document and query. Euclidean distance is calculated
with the formula below.