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RDF

Resource Description Framework — a W3C standard data model where information is expressed as subject-predicate-object triples.

Triple Structure

An RDF triple is the atomic assertion:

Component What it is What it can be
Subject The resource being described IRI or blank node
Predicate The property or relationship IRI
Object The value or related resource IRI, blank node, or literal

A triple asserts a single fact: "subject has property predicate with value object." For example, a triple might assert that a particular model element has a name, or that one element owns another.

Named Graphs

A named graph is a set of triples identified by an IRI (the graph name). Adding the graph name to a triple produces a quad: (subject, predicate, object, graph) — the atomic unit of storage in a [[quadstore]] (Architecture).

Named graphs partition the quadstore into addressable, scopeable sets of triples. Flexo uses this partitioning for:

  • Isolation — separate model data per snapshot, so each commit's model state lives in its own named graph
  • Scoping — target [[SPARQL]] queries and updates to specific graphs rather than the entire store

Named Graph Categories in Flexo

Per project, the [[quadstore]] contains three categories of named graphs (Architecture):

Category Contents
Metadata graph Versioning information: commit history (the DAG), deltas, and refs (branches, tags, locks)
Model graph (snapshot) The entire model data for a given commit. A Snapshot object in the Metadata graph associates a Ref to its materialized Model graph
System graphs Flexo's own state: orgs, repos, collections, access policies, cluster config — stored alongside user data

The Flexo MMS Ontology spans these graphs — classes and their relationships travel both within and across named graphs (Architecture).

In Flexo MMS

  • All model content and all system state are stored as RDF (flexo-mms-layer1-service)
  • Models are handled as RDF graphs, exposed via [[SPARQL]] and [[Graph Store Protocol]] endpoints (Architecture)
  • Not limited to SysML — Flexo can store anything expressed as RDF (openmbee.org)

Toward Formalizing State

The RDF data model gives us a precise notion of "state" in Flexo:

  • The state of a model at a given commit = the set of triples in its snapshot's model graph
  • A commit = a [[SPARQL]] Update (INSERT/DELETE) applied to the parent snapshot's model graph, producing a new model graph
  • The commit DAG tracks lineage; each node implies a model graph (materialized or recoverable)

These are distinct objects — the commit is the change description, the model graph is the resulting state — and the [[Key Insight]] explains why maintaining this distinction is necessary for conflict resolution in structured models.

→ [[Flexo Conflict Resolution Mapping]]

References

← [[Flexo MMS]] · [[Flexo Organization Level]]