Feature flags

The umbrella crate's default feature set is empty. A feature is the only thing that pulls a layer in, so you compile only what you use:

cargo add oxgraph --features csr,algo-std

Features to layers

Feature	Pulls in
`topology`	Core capability traits for discrete topology.
`graph`	Binary graph vocabulary: nodes, edges, directed traversal.
`hyper`	Hypergraph vocabulary: vertices, hyperedges, participants.
`csr`	Compressed-sparse-row graph views over slices.
`csc`	Inbound (compressed-sparse-column) views for reverse traversal.
`hyper-bcsr`	Directed bipartite-CSR hypergraph views.
`snapshot`	Read and validate snapshots (`no_std`, no allocation).
`snapshot-alloc`	Build snapshots (adds `alloc`).
`algo`, `algo-alloc`, `algo-std`	BFS and PageRank at the matching allocation tier.
`graph-build`, `hyper-build`	Append/freeze builders that produce a layout, then a snapshot.
`property-arrow`	Arrow-backed named, typed property layers.
`db`	The embedded database (`oxgraph-db`).
`postgres`	The Postgres-backed engine (also enables `csc`).
`full`	Everything.

Each feature corresponds to a crate in the crate family; you can also depend on those crates directly if you want a tighter dependency graph.

Allocation tiers

Several layers ship at no_std, alloc, and std tiers, so you only pull in an allocator (or std) when your target allows it. oxgraph-algo is the clearest example:

Tier	Feature	For
`no_std`	`algo`	Bare-metal / embedded; you pass in scratch buffers.
`alloc`	`algo-alloc`	Heap available, no `std`.
`std`	`algo-std`	Full standard library.

Snapshots split the same way: snapshot reads and validates without allocating; snapshot-alloc adds the builder.

Borrow, don't parse

Reading a snapshot does not deserialize it. snapshot validates the byte container once and hands back typed slices borrowed straight from the bytes — the bytes → validate → view → traverse pipeline. That is why opening a graph is closer to a memory-map than a parse, and why structures that cross an I/O boundary derive zero-copy layout traits rather than being rebuilt on the heap. See Concepts for the reasoning.