Virtual node concept is a way of creating graphical constructs. A stem from one branch can be made a child of a node in another branch based on relevance, which again has very significant utility. We all know a set of skills may be used in multiple contexts. For example, a design tool like Photoshop may be used by different types of designers including graphic designers, interior designers, fashion designers. Virtual nodes enable us to retain one place for the Graphic Design tools in the association table and have them related or get associated with multiple contexts. So, Graphic Design tools like Photoshop are maintained in one instance but are associated with Graphic Designers, Interior Designers and Fashion Designers.
This means whichever way a person comes from (while creating a Skills Profile) i.e. as a Graphic Designer or Interior Designer or Fashion Designer, they will see the recommendation of Graphic Design tools.
Even if a user comes to more than one of these, they will see the Graphic Design tools. However, this time, it will show that they have already visited and rated on the Graphic Design tool, e.g. Photoshop.