The term expert system comes from the world of artificial intelligence. Originally, it comprised the idea that computer programs can be devised to solve complex problems of decision making, as well as, or even better than human experts. Although in some technical domains this ambitious goal is still valid, it is generally relaxed for applications in legal and administrative domains. Here the term expert system – or knowledge-based system – refers to a category of computer programs that use coded knowledge to help solve problems of decision making. One simple, everyday example is a computer program that helps a tax payer fill in his tax returns and informs him about the implications his answers will have in terms of the amount of tax to be paid. A second, quite different example is a system which, based on a textual summary of a case at hand, can help a legal professional in finding applicable case law.