ABSTRACT:
Sequence labeling is a problem of critical importance in many 
application areas such as speech recognition, natural language 
processing, structure prediction in bioinformatics and video analysis. 
In this tutorial, we present recent methods for solving this problem. 
Sequence labeling requires structured prediction which has to consider 
relations among predicted labels. We will first discuss linear 
classification methods like Fisher's linear discriminant, logistic 
regression and support vector machines in the binary and multi-class 
classification problems. We explain the relation between generative and 
discriminative methods for classification and draw parallels between 
multi-class classification and the sequence labeling problem which can 
be considered as a multi-class classification problem with 
exponentially many classes. The traditional approach of hidden Markov 
models for sequence labeling will be briefly covered. Hidden Markov 
models (HMMs)are generative models of sequential observations. HMMs 
have been used in sequence labeling extensively and remain as a 
powerful approach for many problems. The next topic of interest is 
conditional random fields (CRFs). CRFs have been introduced as a 
discriminative alternative of HMMs and are shown to outperform HMMs in 
some problems. The bottleneck of CRFs is that they are computationally 
harder to train and it may be challenging to apply for continuous 
observations. The tutorial will also explore how CRFs can be used for 
continuous observations. We will also explore the use of max-margin
methods for training linear models similar to CRFs for the sequence 
labeling problem. Max-margin methods similar to support vector machines 
for multi-class classification are interesting methods for effective 
training of linear models for sequence labeling. This approach is also 
called structural SVMs and recently some algorithms for fast training 
of model parameters have been proposed in the literature. Some of these 
methods will be briefly covered in the tutorial.