1 Introduction  
2 Identity Overview  
2.1 Philosophical Problems  
2.2 Practical Problems  
3 Alternative Identity Links  
3.1 Weak-Identity and Similarity Predicates  
3.2 Contextual Identity  
4 Identity Management Services  
4.1 Centralized Identity Management  
4.2 Identity Observatories  
5 Erroneous Identity Links Detection  
5.1 Inconsistency-based Detection Approaches  
5.2 Content-based Approaches  
5.3 Network-based Approaches  
6 Conclusion & Discussion