One type per spec concern.

using OKF4net;

var bundle = Bundle.Load("./my_bundle");           // §3 — permissive walk
var report = BundleValidator.Validate(bundle);      // §9 — diagnostics
Console.WriteLine(report.IsConformant
    ? $"conformant with OKF v{OkfSpec.Version}" : $"{report.ErrorCount} error(s)");

var id = ConceptId.Parse("tables/orders");        // §2
foreach (var link in bundle.LinksFrom(id))          // §5
    Console.WriteLine($"{id} -> {link.Target} (exists: {link.Exists})");
foreach (var back in bundle.Backlinks(id))
    Console.WriteLine($"cited by {back}");

Bundle.Load walks the tree, parses every concept, and builds the cross-link graph. It is permissive: a bad file lands in ParseErrors and never aborts the load.

A concept id is the file path with .md removed, as ordered segments. Sortable and value-equal.

Frontmatter keeps the full ordered mapping and layers typed getters on top, so producer-defined keys survive round-trips. Two validation levels: ValidateConformance() enforces only §9 (non-empty type); Validate() is the stricter producer check (type, title, description, timestamp).

A documented subset: scalars, sequences, shallow maps, block and flow styles, |/> block scalars. It rejects anchors, tags, and multi-document streams with clear errors — frontmatter never needs them.

Every library exception derives from OkfException, so one catch covers the surface. Loading is permissive, so most day-to-day work throws nothing — failures accumulate in ParseErrors instead.

→ cli.md — the same engine as a binary · getting-started.md