Hierarchical Database

• Only allow each child to have one parent
• same tree structure like file system

Network Database

The network database model was a progression from the hierarchical database.

• This model allows each child to have multiple parents

Cons

• The lack of a declarative query mechanism for navigational database management systems.
  • The user would have to tell the database what to do instead of just being able to ask a question and having the database provide the answer.
  • Easy to store data, but hard to get it back out?
• Although more flexible than the hierarchical model, it still has flexibility problems after data is populated
• The programmer still has to understand the data structure well in order to make the model efficient.

Vendor

• CA IDMS
• IBM IMS
• Oracle CODASYL DBMS
• IDS
• Raima Database Manager

Graph database

Graph Query Language

Ref

Cypher

• Developed by Neo4j
• Expressive syntax that closely resembles natural language makes it easy to read
• Providers
  • SAP HANA Graph
  • RedisGraph

Apache Gremlin

• Imperative
• More powerful and flexible than Cypher
• Often compared to SQL in terms of its expressiveness and versatility
• Providers
  • Amazon Neptune
  • Azure Cosmos DB
  • JanusGraph
    • on IBM Bluemix
  • Gremlin-server

SPARQL

• a declarative graph query language
• developed by the World Wide Web Consortium (W3C) as a standard for querying RDF (Resource Description Framework) data.
  • RDF is a data model that is used to represent information on the web
• particularly well-suited for querying linked data and semantic web applications.
• Providers: RDF stores
  • Virtuoso
  • Stardog
  • GraphDB
  • Neo4j
  • Amazon Neptune

Other Vendor

• AllegroGraph
• Dex
• FlockDB
• InfiniteGraph
• OrientDB
• Sones