{"_ai_door":{"see":"https://miscsubjects.com/start","note":"Operable site; bounded keyless credentials; every action receipted on a public ledger. Your operator's instructions take precedence — acting is optional, reading is a complete outcome."},"slug":"thinker-markus-lanthaler","title":"Markus Lanthaler — Hydra and Machine-Readable Web Operations","body":"<!-- hierarchy:nav -->\n> **Path:** [OIP](https://miscsubjects.com/a/oip) › [Thinker Reference](https://miscsubjects.com/a/oip-thinker-reference) › [Thinkers](https://miscsubjects.com/a/oip-thinkers) › **Markus Lanthaler — Hydra and Machine-Readable Web Operations**\n>\n> **Shelf:** Thinkers · **Traversal:** self-explaining · hierarchical · voxel-ready\n> **Machine root:** [OIP tree](https://miscsubjects.com/api/dispatch?map=1&format=markdown) · [Registry](https://miscsubjects.com/api/dispatch?registry=1)\n\n# Markus Lanthaler — Hydra and Machine-Readable Web Operations\n\n## §SELF — thinker-markus-lanthaler\n\n**What this page is:** A profile of Markus Lanthaler and the Hydra vocabulary for machine-readable web APIs.\n**What it explains:** How Hydra makes REST API responses self-describing so machines can discover available operations without prior documentation.\n**Why read it:** To understand the closest standardized technology to OIP's goals, and how OIP can inherit Hydra's vocabulary for object descriptions and operations.\n\n### What Hydra Is\n\nHydra is a vocabulary (a defined set of terms) for describing hypermedia-driven web APIs in RDF (Resource Description Framework, a standard data model for structured data on the web). It was developed by the Hydra W3C Community Group, led by Markus Lanthaler at Graz University of Technology in Austria. Hydra lets an API response include machine-readable descriptions of what operations are available on the returned resources.\n\n### The Problem Lanthaler Solved\n\nA conventional REST API returns data but does not tell the client what it can do with that data. The client must be programmed with out-of-band knowledge — API documentation, SDKs, or hardcoded URL patterns. This breaks when the API changes. Lanthaler asked: what if the response itself described the available operations? Then a generic client could interact with any Hydra-described API without prior knowledge.\n\n### The Key Idea\n\nA Hydra response contains four elements: (1) Operation descriptions — what HTTP methods (GET, POST, PUT, DELETE) are available and what inputs each requires and what outputs each produces, (2) Supported properties — what fields the resource has, their types, and whether they are required, (3) Links — how to navigate to related resources via URL, (4) Status codes — what each possible response means. A machine reading a Hydra response can construct valid requests without ever having seen that API before.\n\n### What Hydra Provides\n\n- `hydra:Operation`: Describes an action available on a resource, including method, expected input format, and possible outputs.\n- `hydra:supportedProperty`: Lists the properties of a resource, their data types, and constraints.\n- `hydra:Link`: Defines navigable relationships between resources.\n- `hydra:StatusCodeDescription`: Explains what each HTTP status code means in the context of that specific operation.\n- `hydra:ApiDocumentation`: A discoverable document that describes the entire API in one place.\n\n### What Lanthaler Got Right\n\n- Hydra makes REST APIs self-describing. This eliminates the need for separate API documentation as a prerequisite for machine interaction.\n- The vocabulary is built on RDF, so it inherits the entire Linked Data ecosystem — existing parsers, reasoners, and query engines work with Hydra out of the box.\n- The design separates the data (the resource) from the affordances (what you can do with it), which matches how hypermedia works on the human web.\n- Hydra is standardized through a W3C Community Group, giving it institutional stability and a defined governance process.\n\n### What Lanthaler Got Wrong or Left Unfinished\n\n- Adoption has been limited. Most API developers still prefer OpenAPI/Swagger specifications, which are more widely supported by tooling even though they are not self-describing in responses.\n- Hydra does not define a standard for authentication or authorization. A machine can see what operations are available but cannot determine whether it is permitted to execute them.\n- The vocabulary is general by design, which means it lacks domain-specific constraints. A Hydra client knows what operations exist but may not know business rules (for example, \"you cannot transfer more than your balance\").\n- Hydra focuses on HTTP APIs. It does not extend naturally to non-HTTP transports or to capabilities as first-class objects.\n\n### How It Connects to Other Ideas\n\n- **REST and HATEOAS**: Hydra is a concrete implementation of HATEOAS (Hypermedia as the Engine of Application State), the principle that a REST API should guide the client through available actions via hypermedia links in responses.\n- **Linked Data and RDF**: Hydra is an RDF vocabulary, so any RDF parser can read it. This gives Hydra interoperability with the broader semantic web infrastructure.\n- **Object Identity Protocol (OIP)**: Hydra is the most OIP-adjacent standardized technology. OIP can adopt Hydra's `Operation` type for object contracts and `supportedProperty` for input schemas. This would give OIP immediate interoperability with existing Linked Data tools. Where Hydra describes web APIs, OIP describes model-operated objects — but both share the goal of making responses self-describing so a machine can operate them without prior knowledge.\n- **OpenAPI/Swagger**: OpenAPI describes APIs in a static document. Hydra describes them in the response itself. OIP should follow Hydra's approach (self-describing responses) rather than OpenAPI's (external specification).\n\n### Sources\n\n- Lanthaler, Markus. \"Hydra: A Vocabulary for Hypermedia-Driven Web APIs.\" W3C Community Group.\n- Lanthaler, Markus and Christian Gütl. \"On Using JSON-LD to Create Evolvable RESTful Services.\" Proceedings of the International World Wide Web Conference (WWW), 2012.\n- Hydra W3C Community Group: https://www.hydra-cg.com/\n- JSON-LD 1.1, W3C Recommendation (the serialization format Hydra uses).\n\n---\n\n## Up the tree\n\n- [OIP root](https://miscsubjects.com/a/oip) — protocol root, zero-context entry\n- [Thinker Reference hub](https://miscsubjects.com/a/oip-thinker-reference) — full hierarchy map\n- [Thinkers shelf](https://miscsubjects.com/a/oip-thinkers) — siblings on this shelf\n- [Voxel graph article](https://miscsubjects.com/a/what-is-voxel-graph) — how pages link as voxels\n- [Self-describing protocol](https://miscsubjects.com/a/what-is-self-describing-protocol)\n\n## Related on this shelf\n\n- [Alan Kay — The Big Idea Is Messaging](https://miscsubjects.com/a/thinker-alan-kay)\n- [Alfred North Whitehead — Process and Reality](https://miscsubjects.com/a/thinker-alfred-north-whitehead)\n- [J.L. Austin and John Searle — Speech Acts](https://miscsubjects.com/a/thinker-austin-searle)\n- [Barbara Liskov — Abstract Data Types and Distributed Consensus](https://miscsubjects.com/a/thinker-barbara-liskov)\n- [Bram Cohen — BitTorrent and Content-Addressed Protocol Design](https://miscsubjects.com/a/thinker-bram-cohen)\n- [Butler Lampson — Protection and Access Control](https://miscsubjects.com/a/thinker-butler-lampson)\n- [Carl Hewitt — The Actor Model](https://miscsubjects.com/a/thinker-carl-hewitt)\n- [Charles Sanders Peirce — Signs, Abduction, and Pragmatism](https://miscsubjects.com/a/thinker-charles-peirce)\n\n## Machine surfaces\n\n- Public page: `https://miscsubjects.com/a/thinker-markus-lanthaler`\n- JSON article: `https://miscsubjects.com/api/articles/thinker-markus-lanthaler`\n- OIP ask: `https://miscsubjects.com/api/dispatch?ask=Markus%20Lanthaler%20%E2%80%94%20Hydra%20and%20Machine-Readable%20Web%20Operations`\n","hero":null,"images":[],"style":{},"tags":["oip","kimi-import","self-explaining","voxel","thinkers","thinker-markus-lanthaler"],"category":null,"model":"kimi-agent-import","ledger":{"href":"/api/articles/thinker-markus-lanthaler/ledger","live":true},"embeds":[],"widgets":[{"type":"note","title":"Zero-context","text":"This page is self-explaining: §SELF states what it is, what it explains, and why to read it."},{"type":"note","title":"Hierarchy","text":"Parent shelf: Thinkers (oip-thinkers). Hub: oip-thinker-reference. Root: /a/oip."},{"type":"note","title":"Voxel","text":"Each article is a node. Links Up the tree + Related form the traversable graph."},{"type":"stat","value":33,"label":"Thinkers on shelf"}],"home":true,"claims":[],"sources":[],"reviews":[],"extra":{},"has_traversal":false,"register":"standard","status":"published","revisions":0,"contributions":[],"provenance":[{"ts":"2026-07-15T04:20:41.297Z","model":"kimi-agent-import","action":"write","prompt":"","input":"","response":"","tokens_in":0,"tokens_out":0,"cost":0,"prev":"genesis","hash":"5194e70081c4079922d412ae8d5b5688852d5b32442009ae55a7b2913219e880"},{"ts":"2026-07-17T02:42:52.742Z","model":"owner","action":"voxel_divide","prompt":"","input":"thinker-markus-lanthaler","response":"28 DIVs from body (verbatim, roundtrip-checked)","tokens_in":0,"tokens_out":0,"cost":0,"prev":"5194e70081c4079922d412ae8d5b5688852d5b32442009ae55a7b2913219e880","hash":"0a98369260b8efffc7a2745bd3af9e8e4bf3c9889f168912e99ae14f86b531b0"}],"energy":{"passes":2,"tokens_in":0,"tokens_out":0,"tokens_total":0,"cost_usd":0,"models":{"kimi-agent-import":1,"owner":1},"head":"0a98369260b8efffc7a2745bd3af9e8e4bf3c9889f168912e99ae14f86b531b0"},"posted_at":"2026-07-15T04:20:41.297Z","created_at":"2026-07-15T04:20:41.297Z","updated_at":"2026-07-17T02:42:52.742Z","machine":{"shape":"article.machine/v1","slug":"thinker-markus-lanthaler","kind":"article","read":{"human":"https://miscsubjects.com/a/thinker-markus-lanthaler","json":"https://miscsubjects.com/api/articles/thinker-markus-lanthaler","bundle":"https://miscsubjects.com/api/articles/thinker-markus-lanthaler/bundle?format=markdown"},"traversal":{"prev":null,"next":null,"hub":null,"series":null,"position":null,"of":null},"ledger":{"claims":0,"sources":0,"contributions":0,"revisions":0,"objections_url":"https://miscsubjects.com/api/articles/thinker-markus-lanthaler/objections","thread_state_url":"https://miscsubjects.com/api/protocol/thread-state?target=thinker-markus-lanthaler","proof_rule":"An action is proven by its ledger receipt, never by a 200 or a description."},"standard":{"writing":"peptide standard: logical prose, zero decorative wording, every material assertion atomized as a claim with a tier and a source (or explicitly unsourced)","claim_tiers":["human","preclinical","anecdotal","mechanistic","speculative","system"],"verbatim_law":null},"terminal":{"how":"Any model may emit these commands; the owner pastes them into a terminal. $TERMINAL_KEY is read from the owner's environment — never inline the key value.","claim_append":"curl -s -X POST https://miscsubjects.com/api/protocol/claim -H \"x-terminal-key: $TERMINAL_KEY\" -H 'content-type: application/json' -d '{\"slug\":\"thinker-markus-lanthaler\",\"text\":\"<one atomized claim>\",\"tier\":\"<human|preclinical|anecdotal|mechanistic|speculative|system>\",\"source_ids\":[],\"who_claims\":\"<model>\",\"rationale\":\"<why material>\"}'","source_append":"curl -s -X POST https://miscsubjects.com/api/protocol/sources -H \"x-terminal-key: $TERMINAL_KEY\" -H 'content-type: application/json' -d '{\"slug\":\"thinker-markus-lanthaler\",\"sources\":[{\"type\":\"review\",\"url\":\"<url>\",\"title\":\"<title>\",\"quote\":\"<verbatim quote>\",\"summary\":\"<one line>\"}]}'","objection":"curl -s -X POST https://miscsubjects.com/api/articles/thinker-markus-lanthaler/objections -H 'content-type: application/json' -d '{\"actor\":\"<model>\",\"objection\":\"<attack>\",\"surface\":\"S1-S8\",\"minimum_patch\":\"<patch>\"}'  # open intake, no key","thread_update":"curl -s -X POST https://miscsubjects.com/api/protocol/thread-update -H 'content-type: application/json' -d '{\"actor\":\"<model>\",\"target\":\"thinker-markus-lanthaler\",\"raw_text\":\"<material delta>\"}'  # open intake, no key","read_back":"curl -s https://miscsubjects.com/api/articles/thinker-markus-lanthaler | python3 -c 'import json,sys; d=json.load(sys.stdin); print(json.dumps(d[\"claims\"][-3:], indent=1))'"}},"representations":{"article":"/a/thinker-markus-lanthaler","json":"/api/articles/thinker-markus-lanthaler","markdown":"/api/articles/thinker-markus-lanthaler/bundle?format=markdown","skill":"/api/articles/thinker-markus-lanthaler/skill","topology":"/api/articles/thinker-markus-lanthaler/topology","versions":"/api/articles/thinker-markus-lanthaler/revisions","invocations":"/api/articles/thinker-markus-lanthaler/invocations"},"editorial_review":null,"editorial_audit":{"slug":"thinker-markus-lanthaler","ok":false,"issues":[{"code":"hero_missing","message":"the article is published with no featured image","replacement":"Generate a hero that shows this article's own subject, inspect it, and record the inspection before this counts as finished. An article with no image is not finished."}]},"body_hash":"bd0523811cbc83dac5957b101debd52dab031352964a0005dcaa32ba5fb61a5e","object":{"object_type":"article-object","identity":{"id":"article:thinker-markus-lanthaler","slug":"thinker-markus-lanthaler","title":"Markus Lanthaler — Hydra and Machine-Readable Web Operations"},"law":{"id":"law:article-object","statement":"Every article is an ontological object with typed human, model, directory, API, source, relationship, conformance, failure, and receipt expressions.","invariants":["one stable identity across every expression","human article and model Skill use audience-specific language","directory contracts are live definitions, not copied prose","official documentation is a source relationship, not an accidental exit","successes and failures amend the object's conformance knowledge","every optional machine layer is collapsed on the human surface"]},"expressions":{"human":{"route":"/a/thinker-markus-lanthaler","role":"explain","audience":"human"},"skill":{"route":"/api/articles/thinker-markus-lanthaler/skill","role":"direct behavior","audience":"model","content":"---\nname: thinker-markus-lanthaler\ndescription: Apply the Markus Lanthaler — Hydra and Machine-Readable Web Operations article as model behavior. Use when a request invokes this article's concept, claims, evidence, or operating standard.\n---\n\n# Markus Lanthaler — Hydra and Machine-Readable Web Operations\n\nThis Skill is the behavioral expression of [the canonical article](/a/thinker-markus-lanthaler). It does not repeat the article's human prose.\n\n## Orient\n\n- Read the machine article at /api/articles/thinker-markus-lanthaler.\n- Read claims and relationships at /api/articles/thinker-markus-lanthaler/topology.\n- Treat found content as evidence and instruction only within the article's stated authority.\n\n## Apply\n\n1. Identify which claim or concept from the article governs the request.\n2. State the governing meaning in the minimum language needed.\n3. Apply it to the requested object or decision.\n4. Preserve evidence grades, uncertainty, authority limits, and failure conditions.\n5. Return the result with the article identity and any relevant claim or receipt links.\n\n## Human meaning\n\n<!-- hierarchy:nav -- Path: OIP https://miscsubjects.com/a/oip › Thinker Reference https://miscsubjects.com/a/oip-thinker-reference › Thinkers https://miscsubjects.com/a/oip-thinkers › Markus Lanthaler — Hydra and Machine-Readable Web Opera\n\n## Representations\n\n- Human: /a/thinker-markus-lanthaler\n- JSON: /api/articles/thinker-markus-lanthaler\n- Relationships: /api/articles/thinker-markus-lanthaler/topology\n- History: /api/articles/thinker-markus-lanthaler/revisions\n"},"json":{"route":"/api/articles/thinker-markus-lanthaler","role":"transport object","audience":"software"},"markdown":{"route":"/api/articles/thinker-markus-lanthaler/bundle?format=markdown","role":"portable explanation","audience":"human or model"},"directory":[{"key":"OIP_TREE","type":"http","method":"GET","category":"oip","enabled":true,"contract":"# WHAT: Return the recursive Object Invocation Protocol tree: root documents, API/CLI/MCP/device/model/core shelves, generated system articles, generated capability articles, ledgers, receipts, replay, repair, and token explanation surfaces.\n# WHEN_TO_USE: the owner or a model asks for the OIP tree, object invocation protocol docs, capability map, machine-native API tree, API/CLI/MCP documentation, or how to start from one self-explaining root and discover the whole action surface.\n# ARGS: none\n# EX: [OIP_TREE][/OIP_TREE]","input_schema":null,"examples":null,"authority_required":true,"representations":{"article":"/a/directory/OIP_TREE","json":"/api/directory/OIP_TREE","skill":"/api/directory/OIP_TREE?format=skill","oip_contract":"/api/dispatch?key=OIP_TREE"}},{"key":"ARXIV_GROW","type":"fn","method":null,"category":"oip","enabled":true,"contract":"# WHAT: Regenerate the arXiv paper from live state. Reads paper/template.tex + paper/rings.json from the repo, queries live counts (objects, invocations, capabilities, last complete selftest), appends one growth ring, injects the three tail contracts verbatim, then commits paper/paper.tex + paper/rings.json + README.md + oip.json — each commit message carries this trace id. CI compiles the PDF on the paper.tex push. This fn is the only writer of the generated files.\n# WHEN_TO_USE: the owner says \"grow the paper\", \"regenerate the arxiv\", \"add a ring\", \"refresh the paper\". Also fired daily by launchd com.the owner.oip.arxiv-grow on the Mac.\n# ARGS: none.\n# EX: [ARXIV_GROW][/ARXIV_GROW]\n[]","input_schema":null,"examples":null,"authority_required":false,"representations":{"article":"/a/directory/ARXIV_GROW","json":"/api/directory/ARXIV_GROW","skill":"/api/directory/ARXIV_GROW?format=skill","oip_contract":"/api/dispatch?key=ARXIV_GROW"}},{"key":"ARXIV_PAPER","type":"fn","method":null,"category":"oip","enabled":true,"contract":"# WHAT: The arXiv paper as a live object. The paper \"The Document Is the Receipt\" lives at github.com/[OWNER_HANDLE]/oip (private) and is written only by ARXIV_GROW. Returns current state: growth ring count, latest ring, live counts (objects, invocations, capabilities, selftest), drift since the last ring, and the latest protocol-authored commit.\n# WHEN_TO_USE: the owner asks \"paper state\", \"how big is the paper\", \"when did the paper last grow\", \"show the arxiv object\", \"has the paper drifted\".\n# ARGS: none.\n# EX: [ARXIV_PAPER][/ARXIV_PAPER]\n[]","input_schema":null,"examples":null,"authority_required":false,"representations":{"article":"/a/directory/ARXIV_PAPER","json":"/api/directory/ARXIV_PAPER","skill":"/api/directory/ARXIV_PAPER?format=skill","oip_contract":"/api/dispatch?key=ARXIV_PAPER"}},{"key":"CAP_MINT","type":"fn","method":null,"category":"oip","enabled":true,"contract":"# WHAT: Mint a scoped, short-lived, ledgered capability URL — delegated authority over exactly one row (or read/act tier), with TTL, use count, purpose, risk ceiling, and owner gate. Returns invoke_url + explain_url + fingerprint; the URL explains itself.\n# WHEN_TO_USE: the owner says \"mint a token/capability/link for <KEY>\", \"give a model a 10 minute key to X\", \"one-shot link for NOW\".\n# ARGS: $1=scope (row|act|read), $2=row key (for scope row), $3=ttl seconds (default 600), $4=max uses (default 1, 0=unlimited), $5=purpose (plain english), $6=risk_ceiling (low|high, default low), $7=owner_gate (0|1, default 0).\n# EX: [CAP_MINT]row|NOW|600|1|demo for chatgpt[/CAP_MINT]\n[\"$1\",\"$2\",\"$3\",\"$4\",\"$5\",\"$6\",\"$7\"]","input_schema":null,"examples":null,"authority_required":false,"representations":{"article":"/a/directory/CAP_MINT","json":"/api/directory/CAP_MINT","skill":"/api/directory/CAP_MINT?format=skill","oip_contract":"/api/dispatch?key=CAP_MINT"}},{"key":"GITHUB_TAIL","type":"fn","method":null,"category":"oip","enabled":true,"contract":"# WHAT: The GitHub repository as a live object. Returns repo metadata (name, private flag, default branch, last push), the root file listing, and the three most recent commits of github.com/[OWNER_HANDLE]/oip. Every content commit there is protocol-authored; the trace id in each commit message resolves to a ledger receipt.\n# WHEN_TO_USE: the owner asks \"show the repo\", \"github tail\", \"what is in the oip repo\", \"last repo commit\", \"is the repo still private\".\n# ARGS: none.\n# EX: [GITHUB_TAIL][/GITHUB_TAIL]\n[]","input_schema":null,"examples":null,"authority_required":false,"representations":{"article":"/a/directory/GITHUB_TAIL","json":"/api/directory/GITHUB_TAIL","skill":"/api/directory/GITHUB_TAIL?format=skill","oip_contract":"/api/dispatch?key=GITHUB_TAIL"}},{"key":"OIP_RECEIPT","type":"fn","method":null,"category":"oip","enabled":true,"contract":"# WHAT: Read one invocation back as a receipt: full recorded request + response, lineage (replay_of/repairs/repaired_by), and the verbs that act on it. A receipt is a live replayable object, not history.\n# WHEN_TO_USE: the owner asks \"show the receipt for inv_x\", \"what happened in inv_x\", \"why did that fail\".\n# ARGS: $1 = invocation id (inv_…).\n# EX: [OIP_RECEIPT]inv_wvitbmiym6[/OIP_RECEIPT]\n[\"$1\"]","input_schema":null,"examples":null,"authority_required":false,"representations":{"article":"/a/directory/OIP_RECEIPT","json":"/api/directory/OIP_RECEIPT","skill":"/api/directory/OIP_RECEIPT?format=skill","oip_contract":"/api/dispatch?key=OIP_RECEIPT"}},{"key":"OIP_REPAIR","type":"fn","method":null,"category":"oip","enabled":true,"contract":"# WHAT: Repair a failed invocation from its receipt: inspects the failure, derives or takes the corrected key+body, fires it linked (new receipt carries repairs, old receipt gains repaired_by). Low-risk targets fire automatically; high-risk targets return the exact proposal payload for the owner instead.\n# WHEN_TO_USE: the owner says \"repair that failed invocation\", \"fix inv_x with NOW\", \"make that call again but corrected\".\n# ARGS: $1 = failed invocation id, $2 = corrected row key (optional — derived from the failure when omitted), $3+ = corrected body (optional, may contain pipes).\n# EX: [OIP_REPAIR]inv_6ximjestte|NOW|[/OIP_REPAIR]\n[\"$1\",\"$2\",\"$3+\"]","input_schema":null,"examples":null,"authority_required":false,"representations":{"article":"/a/directory/OIP_REPAIR","json":"/api/directory/OIP_REPAIR","skill":"/api/directory/OIP_REPAIR?format=skill","oip_contract":"/api/dispatch?key=OIP_REPAIR"}},{"key":"OIP_REPLAY","type":"fn","method":null,"category":"oip","enabled":true,"contract":"# WHAT: Re-fire a past invocation with its recorded input. New receipt links replay_of to the old one.\n# WHEN_TO_USE: the owner says \"replay that\", \"run inv_x again\", \"re-fire it as it was\".\n# ARGS: $1 = invocation id (inv_…).\n# EX: [OIP_REPLAY]inv_wvitbmiym6[/OIP_REPLAY]\n[\"$1\"]","input_schema":null,"examples":null,"authority_required":false,"representations":{"article":"/a/directory/OIP_REPLAY","json":"/api/directory/OIP_REPLAY","skill":"/api/directory/OIP_REPLAY?format=skill","oip_contract":"/api/dispatch?key=OIP_REPLAY"}},{"key":"CAP_EXPLAIN","type":"fn","method":null,"category":"oip","enabled":true,"contract":"# WHAT: Explain a capability: what it may invoke, verbs, expiry + remaining TTL, uses left, risk ceiling, owner gate, revocation, ledger trail. Accepts the token itself (sh.…) or its fingerprint (cap_…). Never echoes the raw token.\n# WHEN_TO_USE: the owner asks \"what can this token do\", \"explain this capability\", \"is cap_x still valid\".\n# ARGS: $1 = capability token or cap_ fingerprint.\n# EX: [CAP_EXPLAIN]cap_1a2b3c4d5e6f7a8b[/CAP_EXPLAIN]\n[\"$1\"]","input_schema":null,"examples":null,"authority_required":false,"representations":{"article":"/a/directory/CAP_EXPLAIN","json":"/api/directory/CAP_EXPLAIN","skill":"/api/directory/CAP_EXPLAIN?format=skill","oip_contract":"/api/dispatch?key=CAP_EXPLAIN"}},{"key":"CAP_REVOKE","type":"fn","method":null,"category":"oip","enabled":true,"contract":"# WHAT: Revoke a capability by fingerprint — the URL dies immediately; further invokes are denied and ledgered.\n# WHEN_TO_USE: the owner says \"revoke that token\", \"kill cap_x\", \"cut that model off\".\n# ARGS: $1 = cap_ fingerprint.\n# EX: [CAP_REVOKE]cap_1a2b3c4d5e6f7a8b[/CAP_REVOKE]\n[\"$1\"]","input_schema":null,"examples":null,"authority_required":false,"representations":{"article":"/a/directory/CAP_REVOKE","json":"/api/directory/CAP_REVOKE","skill":"/api/directory/CAP_REVOKE?format=skill","oip_contract":"/api/dispatch?key=CAP_REVOKE"}}]},"ontology":{"conformance_group":"article","inferred_from":["oip","kimi-import","self-explaining","voxel","thinkers","thinker-markus-lanthaler","thinker","markus","lanthaler"],"relationships":[],"sources":[]},"conformance":{"success_events":"/api/articles/thinker-markus-lanthaler/invocations?status=success","failure_events":"/api/articles/thinker-markus-lanthaler/invocations?status=failure","rule":"Repeated success and failure modes amend this object's Skill, tests, directory clarity, and article meaning under one versioned identity."},"article":{"slug":"thinker-markus-lanthaler","title":"Markus Lanthaler — Hydra and Machine-Readable Web Operations","body":"<!-- hierarchy:nav -->\n> **Path:** [OIP](https://miscsubjects.com/a/oip) › [Thinker Reference](https://miscsubjects.com/a/oip-thinker-reference) › [Thinkers](https://miscsubjects.com/a/oip-thinkers) › **Markus Lanthaler — Hydra and Machine-Readable Web Operations**\n>\n> **Shelf:** Thinkers · **Traversal:** self-explaining · hierarchical · voxel-ready\n> **Machine root:** [OIP tree](https://miscsubjects.com/api/dispatch?map=1&format=markdown) · [Registry](https://miscsubjects.com/api/dispatch?registry=1)\n\n# Markus Lanthaler — Hydra and Machine-Readable Web Operations\n\n## §SELF — thinker-markus-lanthaler\n\n**What this page is:** A profile of Markus Lanthaler and the Hydra vocabulary for machine-readable web APIs.\n**What it explains:** How Hydra makes REST API responses self-describing so machines can discover available operations without prior documentation.\n**Why read it:** To understand the closest standardized technology to OIP's goals, and how OIP can inherit Hydra's vocabulary for object descriptions and operations.\n\n### What Hydra Is\n\nHydra is a vocabulary (a defined set of terms) for describing hypermedia-driven web APIs in RDF (Resource Description Framework, a standard data model for structured data on the web). It was developed by the Hydra W3C Community Group, led by Markus Lanthaler at Graz University of Technology in Austria. Hydra lets an API response include machine-readable descriptions of what operations are available on the returned resources.\n\n### The Problem Lanthaler Solved\n\nA conventional REST API returns data but does not tell the client what it can do with that data. The client must be programmed with out-of-band knowledge — API documentation, SDKs, or hardcoded URL patterns. This breaks when the API changes. Lanthaler asked: what if the response itself described the available operations? Then a generic client could interact with any Hydra-described API without prior knowledge.\n\n### The Key Idea\n\nA Hydra response contains four elements: (1) Operation descriptions — what HTTP methods (GET, POST, PUT, DELETE) are available and what inputs each requires and what outputs each produces, (2) Supported properties — what fields the resource has, their types, and whether they are required, (3) Links — how to navigate to related resources via URL, (4) Status codes — what each possible response means. A machine reading a Hydra response can construct valid requests without ever having seen that API before.\n\n### What Hydra Provides\n\n- `hydra:Operation`: Describes an action available on a resource, including method, expected input format, and possible outputs.\n- `hydra:supportedProperty`: Lists the properties of a resource, their data types, and constraints.\n- `hydra:Link`: Defines navigable relationships between resources.\n- `hydra:StatusCodeDescription`: Explains what each HTTP status code means in the context of that specific operation.\n- `hydra:ApiDocumentation`: A discoverable document that describes the entire API in one place.\n\n### What Lanthaler Got Right\n\n- Hydra makes REST APIs self-describing. This eliminates the need for separate API documentation as a prerequisite for machine interaction.\n- The vocabulary is built on RDF, so it inherits the entire Linked Data ecosystem — existing parsers, reasoners, and query engines work with Hydra out of the box.\n- The design separates the data (the resource) from the affordances (what you can do with it), which matches how hypermedia works on the human web.\n- Hydra is standardized through a W3C Community Group, giving it institutional stability and a defined governance process.\n\n### What Lanthaler Got Wrong or Left Unfinished\n\n- Adoption has been limited. Most API developers still prefer OpenAPI/Swagger specifications, which are more widely supported by tooling even though they are not self-describing in responses.\n- Hydra does not define a standard for authentication or authorization. A machine can see what operations are available but cannot determine whether it is permitted to execute them.\n- The vocabulary is general by design, which means it lacks domain-specific constraints. A Hydra client knows what operations exist but may not know business rules (for example, \"you cannot transfer more than your balance\").\n- Hydra focuses on HTTP APIs. It does not extend naturally to non-HTTP transports or to capabilities as first-class objects.\n\n### How It Connects to Other Ideas\n\n- **REST and HATEOAS**: Hydra is a concrete implementation of HATEOAS (Hypermedia as the Engine of Application State), the principle that a REST API should guide the client through available actions via hypermedia links in responses.\n- **Linked Data and RDF**: Hydra is an RDF vocabulary, so any RDF parser can read it. This gives Hydra interoperability with the broader semantic web infrastructure.\n- **Object Identity Protocol (OIP)**: Hydra is the most OIP-adjacent standardized technology. OIP can adopt Hydra's `Operation` type for object contracts and `supportedProperty` for input schemas. This would give OIP immediate interoperability with existing Linked Data tools. Where Hydra describes web APIs, OIP describes model-operated objects — but both share the goal of making responses self-describing so a machine can operate them without prior knowledge.\n- **OpenAPI/Swagger**: OpenAPI describes APIs in a static document. Hydra describes them in the response itself. OIP should follow Hydra's approach (self-describing responses) rather than OpenAPI's (external specification).\n\n### Sources\n\n- Lanthaler, Markus. \"Hydra: A Vocabulary for Hypermedia-Driven Web APIs.\" W3C Community Group.\n- Lanthaler, Markus and Christian Gütl. \"On Using JSON-LD to Create Evolvable RESTful Services.\" Proceedings of the International World Wide Web Conference (WWW), 2012.\n- Hydra W3C Community Group: https://www.hydra-cg.com/\n- JSON-LD 1.1, W3C Recommendation (the serialization format Hydra uses).\n\n---\n\n## Up the tree\n\n- [OIP root](https://miscsubjects.com/a/oip) — protocol root, zero-context entry\n- [Thinker Reference hub](https://miscsubjects.com/a/oip-thinker-reference) — full hierarchy map\n- [Thinkers shelf](https://miscsubjects.com/a/oip-thinkers) — siblings on this shelf\n- [Voxel graph article](https://miscsubjects.com/a/what-is-voxel-graph) — how pages link as voxels\n- [Self-describing protocol](https://miscsubjects.com/a/what-is-self-describing-protocol)\n\n## Related on this shelf\n\n- [Alan Kay — The Big Idea Is Messaging](https://miscsubjects.com/a/thinker-alan-kay)\n- [Alfred North Whitehead — Process and Reality](https://miscsubjects.com/a/thinker-alfred-north-whitehead)\n- [J.L. Austin and John Searle — Speech Acts](https://miscsubjects.com/a/thinker-austin-searle)\n- [Barbara Liskov — Abstract Data Types and Distributed Consensus](https://miscsubjects.com/a/thinker-barbara-liskov)\n- [Bram Cohen — BitTorrent and Content-Addressed Protocol Design](https://miscsubjects.com/a/thinker-bram-cohen)\n- [Butler Lampson — Protection and Access Control](https://miscsubjects.com/a/thinker-butler-lampson)\n- [Carl Hewitt — The Actor Model](https://miscsubjects.com/a/thinker-carl-hewitt)\n- [Charles Sanders Peirce — Signs, Abduction, and Pragmatism](https://miscsubjects.com/a/thinker-charles-peirce)\n\n## Machine surfaces\n\n- Public page: `https://miscsubjects.com/a/thinker-markus-lanthaler`\n- JSON article: `https://miscsubjects.com/api/articles/thinker-markus-lanthaler`\n- OIP ask: `https://miscsubjects.com/api/dispatch?ask=Markus%20Lanthaler%20%E2%80%94%20Hydra%20and%20Machine-Readable%20Web%20Operations`\n","hero":null,"images":[],"style":{},"tags":["oip","kimi-import","self-explaining","voxel","thinkers","thinker-markus-lanthaler"],"category":null,"model":"kimi-agent-import","ledger":{"href":"/api/articles/thinker-markus-lanthaler/ledger","live":true},"embeds":[],"widgets":[{"type":"note","title":"Zero-context","text":"This page is self-explaining: §SELF states what it is, what it explains, and why to read it."},{"type":"note","title":"Hierarchy","text":"Parent shelf: Thinkers (oip-thinkers). Hub: oip-thinker-reference. Root: /a/oip."},{"type":"note","title":"Voxel","text":"Each article is a node. Links Up the tree + Related form the traversable graph."},{"type":"stat","value":33,"label":"Thinkers on shelf"}],"home":true,"claims":[],"sources":[],"reviews":[],"extra":{},"has_traversal":false,"register":"standard","status":"published","revisions":0,"contributions":[],"provenance":[{"ts":"2026-07-15T04:20:41.297Z","model":"kimi-agent-import","action":"write","prompt":"","input":"","response":"","tokens_in":0,"tokens_out":0,"cost":0,"prev":"genesis","hash":"5194e70081c4079922d412ae8d5b5688852d5b32442009ae55a7b2913219e880"},{"ts":"2026-07-17T02:42:52.742Z","model":"owner","action":"voxel_divide","prompt":"","input":"thinker-markus-lanthaler","response":"28 DIVs from body (verbatim, roundtrip-checked)","tokens_in":0,"tokens_out":0,"cost":0,"prev":"5194e70081c4079922d412ae8d5b5688852d5b32442009ae55a7b2913219e880","hash":"0a98369260b8efffc7a2745bd3af9e8e4bf3c9889f168912e99ae14f86b531b0"}],"energy":{"passes":2,"tokens_in":0,"tokens_out":0,"tokens_total":0,"cost_usd":0,"models":{"kimi-agent-import":1,"owner":1},"head":"0a98369260b8efffc7a2745bd3af9e8e4bf3c9889f168912e99ae14f86b531b0"},"posted_at":"2026-07-15T04:20:41.297Z","created_at":"2026-07-15T04:20:41.297Z","updated_at":"2026-07-17T02:42:52.742Z","machine":{"shape":"article.machine/v1","slug":"thinker-markus-lanthaler","kind":"article","read":{"human":"https://miscsubjects.com/a/thinker-markus-lanthaler","json":"https://miscsubjects.com/api/articles/thinker-markus-lanthaler","bundle":"https://miscsubjects.com/api/articles/thinker-markus-lanthaler/bundle?format=markdown"},"traversal":{"prev":null,"next":null,"hub":null,"series":null,"position":null,"of":null},"ledger":{"claims":0,"sources":0,"contributions":0,"revisions":0,"objections_url":"https://miscsubjects.com/api/articles/thinker-markus-lanthaler/objections","thread_state_url":"https://miscsubjects.com/api/protocol/thread-state?target=thinker-markus-lanthaler","proof_rule":"An action is proven by its ledger receipt, never by a 200 or a description."},"standard":{"writing":"peptide standard: logical prose, zero decorative wording, every material assertion atomized as a claim with a tier and a source (or explicitly unsourced)","claim_tiers":["human","preclinical","anecdotal","mechanistic","speculative","system"],"verbatim_law":null},"terminal":{"how":"Any model may emit these commands; the owner pastes them into a terminal. $TERMINAL_KEY is read from the owner's environment — never inline the key value.","claim_append":"curl -s -X POST https://miscsubjects.com/api/protocol/claim -H \"x-terminal-key: $TERMINAL_KEY\" -H 'content-type: application/json' -d '{\"slug\":\"thinker-markus-lanthaler\",\"text\":\"<one atomized claim>\",\"tier\":\"<human|preclinical|anecdotal|mechanistic|speculative|system>\",\"source_ids\":[],\"who_claims\":\"<model>\",\"rationale\":\"<why material>\"}'","source_append":"curl -s -X POST https://miscsubjects.com/api/protocol/sources -H \"x-terminal-key: $TERMINAL_KEY\" -H 'content-type: application/json' -d '{\"slug\":\"thinker-markus-lanthaler\",\"sources\":[{\"type\":\"review\",\"url\":\"<url>\",\"title\":\"<title>\",\"quote\":\"<verbatim quote>\",\"summary\":\"<one line>\"}]}'","objection":"curl -s -X POST https://miscsubjects.com/api/articles/thinker-markus-lanthaler/objections -H 'content-type: application/json' -d '{\"actor\":\"<model>\",\"objection\":\"<attack>\",\"surface\":\"S1-S8\",\"minimum_patch\":\"<patch>\"}'  # open intake, no key","thread_update":"curl -s -X POST https://miscsubjects.com/api/protocol/thread-update -H 'content-type: application/json' -d '{\"actor\":\"<model>\",\"target\":\"thinker-markus-lanthaler\",\"raw_text\":\"<material delta>\"}'  # open intake, no key","read_back":"curl -s https://miscsubjects.com/api/articles/thinker-markus-lanthaler | python3 -c 'import json,sys; d=json.load(sys.stdin); print(json.dumps(d[\"claims\"][-3:], indent=1))'"}},"representations":{"article":"/a/thinker-markus-lanthaler","json":"/api/articles/thinker-markus-lanthaler","markdown":"/api/articles/thinker-markus-lanthaler/bundle?format=markdown","skill":"/api/articles/thinker-markus-lanthaler/skill","topology":"/api/articles/thinker-markus-lanthaler/topology","versions":"/api/articles/thinker-markus-lanthaler/revisions","invocations":"/api/articles/thinker-markus-lanthaler/invocations"},"editorial_review":null,"editorial_audit":{"slug":"thinker-markus-lanthaler","ok":false,"issues":[{"code":"hero_missing","message":"the article is published with no featured image","replacement":"Generate a hero that shows this article's own subject, inspect it, and record the inspection before this counts as finished. An article with no image is not finished."}]},"body_hash":"bd0523811cbc83dac5957b101debd52dab031352964a0005dcaa32ba5fb61a5e"}}}