Traversal API Prototype for Neo4j

This project is a prototype for a new traversal API for Neo4j.

Design goals include:

• Allowing the same API to be used both for the Embedded Neo4j Graph Database, and with the Neo4j Graph Database Server.
• Being able to express the intent of traversals simply without having to consider complex details.
• Allow for the traversal engine to optimize traversals from the provided traversal declarations.

Traversal modes intended to support:

• Homogeneous traversals.
• Path based traversals, based on simple and complex path expressions.
• Pattern matching traversals.
• Search: A*, shortest path, et.c.
• Combinations of the above.

Design notes

Possible start entities: * Node * Relationship - bidirectional? * Path - bidirectional? * Traversal result * Index hits

Requirements:

• No user defined callbacks
• Define everything through descriptions - cover all common cases
• Possibly leave an "escape hatch" (callback based?) for "advanced" stuff.
• Optionally be able to construct stateful (start position) descriptions from entities.
• Path filtering.

Traversal positioning is:

1. Where I am.
2. How to continue from here.
3. (optionally) carried state.

Traversal is:

1. Positioning
2. Expand candidates
3. Order candidates
4. Evaluate candidates to create next position
5. Repeat