Examples
A policy page explains a rule. An example shows a whole deployment. It covers the configuration file, the policy files, the keys, and the requests sent over the wire with the answers Libra gives. Each page in this section is one complete recipe. Read it as a checklist when you set up something similar.
Every page uses the same conventions. Libra listens on localhost:5667. The NGSI-LD paths a caller uses sit under /ngsi-ld/v1/, and Libra's own endpoints sit under /ngsi-ld/auth/. A caller presents its credential as Authorization: Bearer libra_.... The text after Bearer is printed once, when the key is issued. After that, Libra keeps only a digest of it. A deployment that names tenants takes NGSILD-Tenant.
Every refusal comes back as an RFC 9457 problem document. Its type is a stable URI under https://libra.velacontext.com/problems/. A client error's detail describes the caller's own request. A server error's detail is one fixed sentence, and the real cause goes to the log. 401 means no usable credential. 403 means no policy allows the request, or a restriction refuses it. 404 means the identifier is absent or withheld. 502 and 504 mean the broker failed or was slow. 503 means not ready or too much in flight. The Troubleshooting page has the full map.
| Page | Scenario | What it exercises |
|---|---|---|
| Smart-city fleet | dispatchers see the fleet, never where it is | the attribute restriction, projections against filters, precedence between two allows |
| Multi-tenant dataspace | two tenants on one broker, auditors across both | NGSILD-Tenant, the tenants condition, [multitenancy] |
| Read-only dashboard | charts of the last week, never a reading | the aggregation and time restrictions together |
| Federation | one broker answering for data held behind another Libra | the registrations family, a restriction judging a query at the far hop |
| API key onboarding | issue, verify, rotate, revoke, remove | libra principal and libra key, and what the key store is |
The pages assume Getting started is done. Libra runs from its image in front of a broker, and a policy directory is mounted into it. Each page shows in full what changes between pages. What does not change is described once, here.