Freebase的數據存儲格式叫Graph，nodes定義為/type/object，邊被定義為/type/link.
Freebase文檔中Topic的概念：topic就是entity，topic對應於圖中的節點，但並不是所有的節點都是topic，還有Compound Value Types(組成似的的值類型，例如1997年溫哥華的人口)
Freebase中的Topic有type，而且是一個topic對應多個type，而一個type又類似於一個模板或屬性集合（文檔中把type比作一個relational table）
type的集合叫做domain，每個domain都被分配了id，如：/business, /music等的第一級目錄，而type的標識是第二級目錄，如：/music.album，同樣地，propert是第三級目標，如：/automotive/engine/horsepower
官方發summary：
- A type is a conceptual container of related properties commonly needed to describe a certain aspect of a topic.
- A topic can be assigned one or more types (the default type being
/common/topic) - As properties are grouped into types, types are grouped into domains.
- Domains, types, and properties are given IDs in a namespace/key hierarchy.
- Common well-known topics are given IDs in the
/ennamespace, which are human-readable English strings. - Topics are uniquely identified within Freebase by GUIDs.
- Properties are multi-value by default, and multi-value properties and single-value properties can be queried in the same way.