Databases for dummies
A document-oriented database or document store is a computer program designed for storing, retrieving and managing document-oriented information, also known as semi-structured data. Document-oriented databases are one of the main categories of NoSQL databases, and the popularity of the term “document-oriented database” has grown with the use of the term NoSQL itself. XML databases are a subclass of document-oriented databases that are optimized to work with XML documents. Graph databases are similar, but add another layer, the relationship, which allows them to link documents for rapid traversal.
Document-oriented databases are inherently a subclass of the key-value store, another NoSQL database concept. The difference lies in the way the data is processed; in a key-value store, the data is considered to be inherently opaque to the database, whereas a document-oriented system relies on the internal structure of the document in order to extract metadata that the database engine uses for further optimization. Although the difference is often moot due to tools in the systems, conceptually the document-store is designed to offer a richer experience with modern programming techniques.
Document databases contrast strongly with the traditional relational database (RDB). Relational databases generally store data in separate tables that are defined by the programmer, and a single object may be spread across several tables. Document databases store all information for a given object in a single instance in the database, and every stored object can be different from every other. This makes mapping objects into the database a simple task, normally eliminating anything similar to an object-relational mapping. This makes document stores attractive for programming web applications, which are subject to continual change in place, and where the speed of deployment is an important issue.