Stemming is a common word conflation method that perceives stems embedded in the words and decreases them to their stem (root) by conflating all the morphologically related terms into a single term, without doing a complete morphological analysis. This article presents STEMUR, an enhanced stemming algorithm for automatic word conflation for Urdu language. In addition to handling words with prefixes and suffixes, STEMUR also handles words with infixes. Rather than using a totally unsupervised approach, we utilized the linguistic knowledge to develop a collection of patterns for Urdu infixes to enhance the accuracy of the stems and affixes acquired during the training process. Additionally, STEMUR also handles English loan words and can handle words with more than one affix. STEMUR is compared with four existing Urdu stemmers including Assas-Band and the template-based stemmer that are also implemented in this study. Results are processed on two corpora containing 89,437 and 30,907 words separately. Results show clear improvements regarding strength and accuracy of STEMUR. The use of maximum possible infix rules boosted our stemmer's accuracy up to 93.1% and helped us achieve a precision of 98.9%.

The research work in this paper discusses an improved Petri net model of railway crossing regions which are important and critical components of a railway networks. A control algorithm has been developed showing the interaction of the controller to other component of the system. A formal approach viz. Petri net (PN) is applied to model the safety requirement of trains along the crossing regions in railway networks. For the modeling, the component based modeling and the state-oriented modeling approaches have been integrated. First the track components and the control component are identified. The interaction of identified components, satisfying the safety requirements, is also defined in the high level architecture. Finally, state-oriented modeling approach has been adopted to design the detailed model of crossing region. Further, this paper uses the coverability tree to verify the specifications of crossing regions. By taking the crossing point as center, a circular region is introduced for safety purpose. Further, safety properties have been defined in term of place-invariants which have been verified by the state-space analysis.