Does they correctly use word "Semantic". It may be OK for algorithm title(Latent Semantic Analysis), but results not so "Semantic", it is usual topic detection based on vector-space model. Usually "Semantic analysis" corresponds to next to syntactic level of analysis, some kind of understanding. We have no such analysis here. Also imho(not only my), word "Semantic" is marker for oil snake trader. Is there some quality measures? This algorithm gives 20% of other topic for random article in average.