Agile Development & Interaction with Developers

Question

I have read in few blogs that as part of agile development , the product owner closely interact with developers to state their requirements and come up with a solution. However in case of a large project (in terms of number of applications involved) involving multiple systems , is this possible? Shouldn't the project have a business analyst / solution designer in order to capture the requirements properly and come up with a solution which states how the the requirement could be fulfilled and which systems must do what activity?