For you who have no single idea about what is going to be discussed in this discourse, the first thing you need to know is what SME stands for. SME is short for subject-matter expert, could also be called as a domain expert. This kind of expert is a person who specializes in being an authority of software for a certain area or topic. It means that to be able to be a subject-matter expert; one should have knowledge at least in two different domains. For example, if there be software for accounting to be made, it should be made by someone who has knowledge in accountancy and software.
As for the project, subject-matter experts often work in a team. The role of the subject-matter experts in the project is to provide a strategy and find a solution for the customer organization of business. To be able to do so, they need to get as much accurate input into the current processes of the business.