How to facebookAPI designed

I have a few experience for design database and when I use a Facebook API I wonder with a object-id facebook. why facebook knows what kind of objectId is, such as I call Facebook API where facebook.com/post_id, page_id, event or note ,how facebook knows that it's a post_id or note and facebook knows post_id can use which edges and note also sometime they are different edges.So I would like to know how to design database like this

Something like this

And this

Can you recommend me about documents or desgin pattern something likes this?