I need to link facts to actions through rules. If a person bought soup 10 times and he is coming at midday every day, then the system should link the fact that the person bought soup so many times, using the rule "person, consecutively buying soup 5 or more times within a month is going to buy soup with 90% confidence", to the conclusion that with 90% confidence today at midday, the same person will show up, ordering soup.
Above is an example of an expert system, however based on the research I've just done, it seems like expert systems have lost their popularity, which they had in 90s-00s. The only "popular" applications are business decision making and some medical systems. I am wondering if I should use expert systems or should I look into more "advanced" alternatives? What are the obvious disadvantages to using an expert system, besides the setup cost of conducting the research?