Do I have to create a owl for my app?

I’am planning to create a online chatting app based on solid. I’ve followed this guide: solid-angular and successfully serve the sample application.
But I found that the owl used in the sample application: is not very suitable to my chatting app idea.
Do I have to create my own owl (and how)? Or there are some other suggestion owls.
And I found that the property of RDF is always one direction e.g: Alice knows Bob. Is there anyway to describe a bidirectional property? e.g: Alice <-friends-> Bob