sample semantic explicit relations : 
1 eating together regularly
2 coding together regularly
3 met in clubhouse
4 worked in same project at XXX company
5 did a podcast together

these relations can either describe regular interactions or one-time interactions.

I can think of 2 use cases for semantic explicit relations : 
1 help users better understand their 2nd or higher degree connections by giving information on how exactly these connections connect with users' friends
2 build edge-semantic-explicit social graphs(may need nlp aggregation) for more powerful analysis

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