基本概念和术语

在本章中，我们将讨论ArangoDB的基本概念和术语。掌握与我们正在处理的技术主题相关的基本术语是非常重要的。

ArangoDB的术语如下所示−

• 文件
• 收藏
• 集合标识符
• 集合名称
• 数据库
• 数据库名称
• 数据库组织

从数据模型的角度来看，ArangoDB可以看作是一个面向文档的数据库，因为文档的概念是后者的数学思想。面向文档的数据库是NoSQL数据库的主要类别之一。

层次结构是这样的：文档被分组到集合中，集合存在于数据库中

显然，Identifier和Name是集合和数据库的两个属性。

通常，存储在文档集合中的两个文档（顶点）由存储在边集合中的文档（边）链接。这是ArangoDB的图形数据模型。它遵循有向标记图的数学概念，只是边不仅仅有标签，而且是完整的文档。

Having become familiar with the core terms for this database, we begin to understand ArangoDB’s graph data model. In this model, there exist two types of collections: document collections and edge collections. Edge collections store documents and also include two special attributes: first is the _从 attribute, and the second is the _至 attribute. These attributes are used to create edges (relations) between documents essential for graph database. Document collections are also called vertex collections in the context of graphs (see any graph theory book).

Let us now see how important databases are. They are important because collections exist inside databases. In one instance of ArangoDB, there can be one or many databases. Different databases are usually used for multi-tenant setups, as the different sets of data inside them (collections, documents, etc.) are isolated from one another. The default database _系统 is special, because it cannot be removed. Users are managed in this database, and their credentials are valid for all the databases of a server instance.