Graph model

Deliver an online site where patients can view and respond to a series of questions that help to determine their eligibility for a clinical trials*. A patient should be able to save their data and come back at a later date to update or complete the survey. 

I was asked to draw a model for surveys recently. The surveys have questions and answers. A few years back I worked on a system that popped up questions in order to diagnose problems reported by customers. So based on the answers new questions will be posed on a site to enable diagnosis. So at that time we used a RDBMS and it did not seem to be a natural way of representing complex branches of questions and answers.

Now I realize a graph model represented in Neo4J graph DB can be a more flexible model. So a graph looks like a more realistic model of a survey.

1. A proper model matching the problem
2. Versioning and storage of historical records of entire surveys are possible
3. Querying for historical records based on timestamped versions is possible. In this case ‘TimeUnit’ can be shown as a first-class graph node and not just data in a RDBMS.
4. Reusability of answers and questions are clearly represented.

I am neither a RDBMS expert or a graph expert but the model shown below seems flexible enough.