CHPG/QL

Compound Hierarchal Property Graph and Query Language

CHPG is a lightweight graph database for storing property graphs (attributed, multi-relational graphs) with hierarchical and compound relationships. Like SQLite, which serves as an embedded database that can be serialized to a single single cross-platform file format, CHPG is a queryable in memory graph database that serializes to a single cross-platform file format. The graph APIs and query language mimic much of the design and user experience of the Atlas program graph and query language, but is not specific to code property graphs.

Nodes and Edges

Both nodes and edges in SPGQLite are GraphElement objects. GraphElement objects are uniquely addressed and equality is based on the equality of the addresses between the given graph elements. A Node is simply a GraphElement, but an Edge consists of two Nodes that form a directed edge between the from node and the to node.

Attributes and Tags

All GraphElement objects contain an attribute map that maps a String attribute key to an Object value. Conceptually, a tag is an attribute whose value is true, of which the presence of the tag denotes that the GraphElement is a member of a set. Nodes and edges can be queried in a graph by selecting by the presence of a tag or attribute or by filtering by GraphElement objects with the given attribute and attribute value.

Tag Hierarchy

All tags denote a set membership, however some tags may be implicit depending defined the tag hierarchy relationships.

Containment Edges

Containment edges are hierarchal edge tags that denote structural nesting of nodes and form compound nodes.

Graph Schema

• TODO: document

Query Language

• TODO: document

Serialization

• TODO: document

TODOs

See TODO.md.