E-mail signature block analysis

Hao Chen, Jianying Hu, and Richard Sproat

The signature block is a common structured component found in e-mail
messages.  Accurate identification and analysis of signature blocks
are important in many multimedia messaging and information retrieval
applications such as e-mail text-to-speech rendering.  It is also a
very challenging task, because signature blocks often appear in
complex two-dimensional layouts which are guided only by loose
conventions.  Traditional text analysis methods designed to deal with
sequential text cannot handle 2-dimensional structures, while the
highly unconstrained nature of signature blocks makes the application
of 2-dimensional grammars very difficult.  In this paper we describe
an algorithm for signature block analysis which combines
two-dimensional structural segmentation with one-dimensional
grammatical constraints. The information obtained from both
geometrical and linguistic analysis are integrated in the form of
weighted finite state transducers (WFST), and the final solution is
the optimal interpretation under both constraints.