Experiments in topic indexing of broadcast news using neural networks

The paper deals with the problem of extracting topic information from news show stories by statistical methods. It is shown that the traditional topic-dependent n-gram language modeling approach can be decomposed in order to apply neural networks for topic indexing. Two specific problems in training of these networks are addressed: a very sparse data distribution in the stories and the superposition of different topics in a story. The first problem is tackled by an integrated smoothing approach in the backpropagation method; an expansion of the neural network structure can be used to cope with topic mixtures in stories. Due to the efficient parameter sharing the application of neural networks results in a small improvement in topic indexing performance on a small corpus of broadcast news compared to the traditional topic-dependent n-gram method.