One database,
endless history

(: Rev 1 — store initial data :)
sirix> jn:store('shop','products','[
          {"name":"Laptop", "price":999},
          {"name":"Phone",  "price":699}
        ]')

(: Rev 2 — price drop on the laptop :)
sirix> let $doc := jn:doc('shop','products')
       return replace json value of $doc[0].price with 899

(: Rev 3 — add a new product :)
sirix> let $doc := jn:doc('shop','products')
       return append json {"name":"Tablet","price":449} into $doc

(: Rev 4 — discontinue the phone :)
sirix> let $doc := jn:doc('shop','products')
       return delete json $doc[1]

(: Time travel — what was the original catalog? :)
sirix> jn:open('shop','products', 1)
=> [{"name":"Laptop","price":999}, {"name":"Phone","price":699}]

(: Track how the laptop price evolved across revisions :)
sirix> let $item := sdb:select-item(jn:doc('shop','products'), 6)
       for $v in sdb:item-history($item)
       return {"rev": sdb:revision($v), "price": $v}
=> {"rev":1, "price":999}
   {"rev":2, "price":899}

(: How did the catalog evolve across all revisions? :)
sirix> for $v in jn:all-times(jn:doc('shop','products'))
       return {"rev": sdb:revision($v), "products": count($v[])}
=> {"rev":1, "products":2}
   {"rev":2, "products":2}
   {"rev":3, "products":3}
   {"rev":4, "products":2}

(: What changed between rev 1 and the latest? :)
sirix> jn:diff('shop','products', 1, 4)
=> {"diffs": [
     {"update": {"path":"/[0]/price", "value":899}},
     {"insert": {"path":"/[1]", "data":"{\"name\":\"Tablet\"}"}},
     {"delete": {"path":"/[1]"}}
   ]}█