Which verifiable data structure does sovrin ledger have?

Is the data structure underpinning Sovrin a:

(i) verifiable map? or
(ii) verifiable log-backed map?

Using the classic definitions here:

“verifiable log-backed map”. There are multiple of these for different purposes, with one verifiable log determining order of events across those multiple logs. The “verifiable log” part is the ledger and the “map” part is a patricia trie. In addition to the “map”, there is one more merkle tree for each ledger but this tree is used for producing inclusion proof of events. For more details, refer this and this.