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One pretty easy way to include some “built-in” database documentation for your databases (which could be the beginnings of a data dictionary) is to add extended properties on your objects.

Placing a document under version control is very unintrusive. Vermongo only adds a version number property (an int32 called _version) to the document. It does not touch any other fields. In particular, it also does not place any requirements on the contents of the _id field. Older revisions are stored in a separate collection that shadows the original collection. They are MongoDB documents themselves, and can be queried.

When creating, updating, or deleting documents, you just have to follow the Vermongo protocol outlined here. There will be (at least) a Java library to facilitate this. The only major downside is that documents have to be updated one-by-one (no bulk updates possible), and that there is some overhead in retrieving and copying the old version. Query operations can just proceed as normal.

After inserting into collection 'foo' a document { a=>"x"}, updating it to { a: "y"}, then to { a: "z" }, and finally deleting it, the shadow collection will contain the following (the original collection will not contain the document anymore, as it has been deleted): > db.foo.vermongo.find() { "_id" : { "_id" : ObjectId("4c78da..."), "_version" : 1 }, "a" : "x", "_version" : 1 } { "_id" : { "_id" : ObjectId("4c78da..."), "_version" : 2 }, "a" : "y", "_version" : 2 } { "_id" : { "_id" : ObjectId("4c78da..."), "_version" : 3 }, "a" : "z", "_version" : 3 } { "_id" : { "_id" : ObjectId("4c78da..."), "_version" : 4 }, "_version" : "deleted:4" }