For example, in Chinese online chat, "雷(lei)" becomes popular to express "shock" emotion; 2) Emotion keywords often have multi-senses, and hence the problem of word ambiguity cannot be avoided; 3) Emotion context also has the problem of context shift as the sentiment shift (Polanyi and Zaenen, 2004).
even in formal text, emotion detection and classification is not a simple task, and it is a complicated job, which requires in-depth semantic understanding of texts.