Expert Systems are a type of Artificial Intelligence (AI) that are designed to mimic the decision-making abilities of a human expert in a specific domain. Some of the main enterprise providers of Expert Systems include:

1. IBM Watson: IBM’s Watson platform offers a range of expert system tools, including Watson Studio, which allows businesses to build, train and deploy expert systems, and Watson Assistant, which allows businesses to build and deploy conversational AI.
2. Artificial Solutions: Artificial Solutions provides an expert system platform called Teneo, which allows businesses to build, train and deploy conversational AI and expert systems for natural language understanding and generation.
3. Inbenta: Inbenta is an expert system provider that specializes in natural language processing (NLP) and natural language understanding (NLU) technologies, and offers a range of expert systems for customer service chatbots, search engines and virtual assistants.
4. Expert System: Expert System is an expert system provider that specializes in semantic intelligence and natural language processing (NLP) technologies, and offers a range of expert systems for text analytics, information retrieval, and content management.
5. Infosys Nia: Infosys Nia is an expert system platform that allows businesses to build, train and deploy expert systems for natural language understanding, text analytics, and data integration.
6. CogniCor: CogniCor is an expert system provider that offers a range of expert systems for customer service chatbots, virtual assistants, and call center automation.

These providers offer a range of expert systems and tools, but they all have their own strengths and weaknesses. IBM Watson is known for its ability to integrate with other IBM products and its wide range of services. Artificial Solutions is known for its ability to provide natural language understanding and generation. Inbenta and Expert System are known for their expertise in natural language processing (NLP).