Prior to starting an AI project, the first choice you need to make is whether to use an expert system (a rules based system) or machine learning. Basically the choice comes down to the amount of data, the variation in that data and whether you have a clear set of steps for extracting a solution from that data. An expert system is best when you have a sequential problem and there are finite steps to find a solution. Machine learning is best when you want to move beyond memorizing sequential steps, and you need to analyze large volumes of data to make predictions or to identify patterns that you may not even know would provide insight — that is, when your problem contains a certain level of uncertainty.

Think about it in terms of an automated phone system.

Older phone systems are sort of like expert systems; a message tells the caller to press 1 for sales, 2 for customer service, 3 for technical support and 4 to speak to an operator. The system then routes the call to the proper department based on the number that the caller presses.

Newer, more advanced phone systems use natural language processing. When someone calls in, the message tells the caller to say what they’re calling about. A caller may say something like, “I’m having a problem with my Android smart phone,” and the system routes the call to technical support. If, instead, the caller said something like, “I want to upgrade my smartphone,” the system routes the call to sales.

The challenge with natural language processing is that what callers say and how they say it is uncertain. An angry caller may say something like “That smart phone I bought from you guys three days ago is a piece of junk.” You can see that this is a more complex problem. The automated phone system would need accurate speech recognition and then be able to infer the meaning of that statement so that it could direct the caller to the right department.

With an expert system, you would have to manually input all the possible statements and questions, and the system would still run into trouble when a caller mumbled or spoke with an accent or spoke in another language.

In this case, machine learning would be the better choice. With machine learning, the system would get smarter over time as it created its own patterns. If someone called in and said something like, “I hate my new smart phone and want to return it,” and they were routed to sales and then transferred to customer service, the system would know that the next time someone called and mentioned the word “return,” that call should be routed directly to customer service, not sales.

When you start an AI program, consider which approach is best for your specific use case. If you can draw a decision tree or flow chart to describe a specific task the computer must perform based on limited inputs, then an expert system is probably the best choice. It may be easier to set up and deploy, saving you time, money and the headaches of dealing with more complex systems. If, however, you’re dealing with massive amounts of data and a system that must adapt to changing inputs, then machine learning is probably the best choice.

Some AI experts mix these two approaches. They use an expert system to define some constraints and then use machine learning to experiment with different answers. So you have three choices — an expert system, machine learning or a combination of the two.