This book constitutes the refereed proceedings of the 21st International Conference on Applications of Natural Language to Information Systems, NLDB 2016, held in Salford, UK, in June 2016.The 17 full papers, 22 short papers, and 13 poster papers presented were carefully reviewed and selected from 83 submissions.

A Methodology for Biomedical Ontology Reuse.- Tamil Morphological Analyzer Using Support Vector Machines.- The Role of Community Acceptance in Assessing Ontology Quality.- How to Complete Customer Requirements: Using Concept Expansion for Requirement Refinement.- An Information Gain-Driven Feature Study for Aspect-Based Sentiment Analysis.- ESSOT: An Expert Supporting System for Ontology Translation.- Adapting Semantic Spreading Activation to Entity Linking in Text.- Evaluating Multiple Summaries without Human Models: A First Experiment with a Trivergent Model.- PatEx: Pattern Oriented RDF Graphs Exploration.- Multilingual Protest Event Data Collection with GATE.- A Multi-lingual Approach to Improve Passage Retrieval for Automatic Question Answering.- Information Extraction on Weather Forecasts with Semantic Technologies.- Keyword Identification Using Text Graphlet Patterns.- Disentangling the Structure of Tables in Scientific Literature.- Extracting and Representing Higher Order Predicate Relations between Concepts.- Towards Evaluating the Impact of Anaphora Resolution on Text Summarization from a Human Perspective.- An LDA-based Approach to Scientific Paper Recommendation.- Topic Shifts in Stack Overflow: Ask it Like Socrates.- Semantic-Syntactic Word Valence Vectors for Building a Taxonomy.- Generating Tailored Classification Schemas for German Patents.- A Platform Based ANLP Tools for the Construction of An Arabic Historical Dictionary.- Extracting Knowledge Using Wikipedia Semi-Structured Resources.- Mixing Crowdsourcing and Graph Propagation to Build a Sentiment Lexicon: Feelings Are Contagious.- Comparing Two Strategies for Query Expansion in a News Monitoring System.- An Active Ingredients Entity Recognizer System Based on Profiles.- Improving the Sentiment Analysis Process of Spanish Tweets with BM25.- Validating Learning Outcomes of An E-Learning System Using NLP.- Aspects from Appraisals!! A Label Propagation with Prior Induction Approach.- Mining HiddenKnowledge from the Counterterrorism Dataset Using Graph-Based Approach.- An Empirical Assessment of Citation Information in Scientific Summarization.- PIRAT: A Personalized Information Retrieval System in Arabic Texts Based on a Hybrid Representation of a User Profile.- YATS: Yet Another Text Simplifier.- Are Deep Learning Approaches Suitable for Natural Language Processing.- An Approach to Analyse A Hashtag-Based Topic Thread in Twitter.- Identification of Occupation Mentions in Clinical Narratives.- Multi-Objective Word Sense Induction Using Content and Interlink Connections.- Re-expressing Business Processes Information from Corporate Documents into Controlled Language.- Using Semantic Frames for Automatic Annotation of Regulatory Texts.- Automatic Evaluation of a Summary's Linguistic Quality.- Extracting Formal Models from Normative Texts.- Sentiment Analysis in Arabic.- Automatic Creation of Ontology Using a Lexical Database: An Application for the Energy Sector.- Computer-generated Text Detection Using Machine Learning: A Systematic Review.- Sentiment Analysis for German Facebook Pages.- An Information Retrieval Based Approach for Multilingual Ontology Matching.- Automatic Text Summarization with a Reduced Vocabulary Using Continuous Space Vectors.- A Platform for the Conceptualization of Arabic Texts Dedicated to the Design of the UML Class Diagram.- Reversing the Polarity with Emoticons.- Spatial-Temporal Representation and Reasoning About Objects and Regions.- Bias Based Navigation for News Articles and Media.- Learning to Rank Entity Relatedness through Embedding-Based Features.- Arabic Quranic Search Tool Based On Ontology.