JSON/BSON

MongoDB is a JSON document database.

You can think of a Mongo document as similar to what a row is in a relational table, but with the difference of not having a schema.

Therefore, a given Mongo document can have fields that no other documents have in the same database. This gives you a lot of flexibility when your data is heterogeneous and you can not anticipate all the details of the schema in advance.

JSON

JSON is a data representation format based on plain text.

The following is an example of how JSON could be used for representing data about Movies

{
title: "Forrest Gump",
year: 1994,
director: "Robert Zemeckis",
writers: [ "Winston Groom", "Eric Roth" ],
stars: [ "Tom Hanks", "Robin Wright", "Gary Sinise" ]
}

and

{
title: "The Matrix",
year: 1999,
directors: [ "Andy Wachowski", "Lana Wachowski" ],
writers: [ "Andy Wachowski", "Lana Wachowski" ],
stars: [ "Keanu Reeves", "Laurence Fishburne", "Carrie-Anne Moss"]
}

Overall, the representation is composed of Key-Value pairs.

• A ”:” symbol connect the key with the value.
• Multiple key-value pairs are separated by commas.
• Values that have multiple entries (arrays) are grouped in square brackets “[...]”.

The data structure can be nested, and this provides a great deal of flexibility on how data can be represented.

BSON

MongoDB uses BSON as the data storage and network transfer format for “documents”.

• BSON is a binary encoded serialization of JSON-like documents.
• BSON is designed to be lightweight, traversable, and efficient.
• BSON, like JSON, supports the embedding of objects and arrays within other objects and arrays.

BSON at first seems BLOB-like, but the Mongo database understands BSON internals. This means that MongoDB can “reach inside” BSON objects, even nested ones. Among other things, this allows MongoDB to build indexes and match objects against query expressions on both top-level and nested BSON keys.