If you are looking to use PI Vision extensibility to develop a custom symbol, then the data item that is passed to the dataUpdate method has a metadata field called Path that contains exactly what you want.
To reduce the response size and improve performance, these metadata fields are returned on the first request and only periodically afterward. The symbol update code should only process updates for these fields if they actually exist in the response.
You can use scope.symbol.datasources and scope.runtimeData.metaData to get datastreams. This includes PI and AF attributes.
Lal Babu Shaik