Semi-Supervised Granular Classification Framework for Resource Constrained Short-texts: Towards Retrieving Situational Information During Disaster Events.

During the time of disasters, lots of short-texts are generated containing crucial situational information. Proper extraction and identification of situational information might be useful for various rescue and relief operations. Few specific types of infrequent situational information might be critical. However, obtaining labels for those resource-constrained classes is challenging as well as expensive. Supervised methods pose limited usability in such scenarios. To overcome this challenge, we propose a semi-supervised learning framework which utilizes abundantly available unlabelled data by self-learning. The proposed framework improves the performance of the classifier for resource-constrained classes by selectively incorporating highly confident samples from unlabelled data for self-learning. Incremental incorporation of unlabelled data, as and when they become available, is suitable for ongoing disaster mitigation. Experiments on three disaster-related datasets show that such improvement results in overall performance increase over standard supervised approach.