Is there such a thing as a schema in a graph database?

Question

Is there such a thing as a schema in a graph database? For example, can you specify which types of node can have relationships with which other types of node?

What does such a schema look like?

Bear in mind that graph databases are far from being as standardized as relational databases adhering to a certain SQL version. So I think it depends on what graph database you use. — das_weezul, Jul 29 '11 at 18:31

score 4 · Answer 1 · answered Jan 02 '14 at 15:45

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Yes. Schemas useful in selecting vertex labels, which are part both Neo4J 2 and Tinkerpop 3. I think writing down the schema helps clarify how the graph should be used, although most databases don't support validations against a schema.

I have a longer post on how to draw the schema as a graph. http://lambdazen.blogspot.com/2014/01/do-property-graphs-have-schemas.html

answered Jan 02 '14 at 15:45

Sridhar Ramachandran

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I was very interested in your blogpost. Sadly the link is broken. – MrIsaacs May 07 '19 at 05:53

score 4 · Answer 2 · edited May 23 '17 at 12:24

Graph databases differ a lot in this area, just like das_weezul says. In the general case I think graph databases which are closer to object databases (OODB) also have built-in schema support. One nice thing about graph databases is that they're very well suited for mixing data and metadata. So a common approach for both dealing with schema support and security is to store this kind of metadata in a (sometimes hidden) part of the very same graph.

When it comes to Neo4j - where I'm on the team - there's currently at least two approaches in use for defining schemas:

Defining the schema in annotations, for example using Spring Data Graph (docs).
Using a meta-model layer on top of the database.

You'll find some more reading on this topic over at myNoSQL.

score 3 · Answer 3 · answered Jul 30 '11 at 14:00

A graph database will always have a rudimentary schema consisting of (at least) Vertex and Edge objects, where an Edge can contain data about a particular relationship. The degree to which you can add to this schema varies widely across implementations. You may be able to customize the schema by inheriting from Edge and/or Vertex objects,for instance.

If the graph database uses an underlying RDBMS or ODBMS then you may have access to more powerful schema creation and manipulation capabilities.

Is there such a thing as a schema in a graph database?

3 Answers3