[{"employee":"Joe","areAllAttributesMatched":false,"characteristics":[{"step":"A","name":"house","score":"1"},{"step":"B","name":"car"},{"step":"C","name":"job","score":"3"}]}]

db.collection.aggregate([{"$unwind":"$characteristics"},{"$match":{"characteristics.score":{"$exists":false}}},{"$project":{"employee":1,"name":"$characteristics.name","step":"$characteristics.step",_id:0}}])