# IRI Link Relation: `read-file-head` **Relation URI:** `https://iri.science/rels/read-file-head`
**CURIE:** `iri:read-file-head`
**Status:** Provisional
**Version:** 1.0.0
**Change controller:** IRI technical subcommittee
**Source representation type:** Eligible DOE-IRI `Resource` representation with an explicit filesystem operation context
**Source resource type:** One of the exact Resource Types enumerated in Section 3
**Target representation type:** Resource-specific asynchronous file-head operation entry point
**OpenAPI operation:** `POST /api/v2/filesystem/head/{resource_id}` (`operationId: head`) This document defines the `iri:read-file-head` operation-affordance relationship used by eligible DOE-IRI Resource representations. The canonical relation URI is `https://iri.science/rels/read-file-head`. With the canonical IRI CURIE template `https://iri.science/rels/{rel}`, `iri:read-file-head` expands to that URI. The relation URI identifies the link-relation semantics and is distinct from any target representation profile. ## 1. Relationship Metadata | Field | Definition | |---|---| | Relationship | `iri:read-file-head` | | Relation URI | `https://iri.science/rels/read-file-head` | | Status and version | `provisional`, version `1.0.0` | | Change controller | IRI technical subcommittee | | Semantic meaning | Identifies the applicable operation entry point for requesting the beginning of files in the source Resource's filesystem context. | | Source representation type | DOE-IRI `Resource` representation with one of the exact Resource Types in Section 3 and an explicit, unambiguous filesystem adapter and path context. | | Target representation type | Resource-specific asynchronous file-head operation entry point. | | Cardinality | `0..1` link from each eligible source Resource representation. | | Applicability | The adapter implements the mapped operation for the represented Resource and establishes its filesystem namespace and execution/access context. | | Target stability | Configured operation affordance, not a current file-content, reachability, or successful-read assertion. | | Relationship volatility | Changes when the facility configures or withdraws the applicable adapter operation or changes requester-visible discovery, not solely because operational conditions change. | | Authorization affects visibility | Yes. The relation MAY be omitted when the requester is not authorized to discover or invoke the entry point. Presence grants no permission. | | Omission semantics | Not advertised in this representation; omission does not prove that file-head reading is unsupported everywhere or permanently unavailable. | | Target classification | Operation entry point; not an API resource, DOE-IRI typed Resource, file content, read result, or representation profile. | | OpenAPI operation | `POST /api/v2/filesystem/head/{resource_id}` with `operationId: head`; success returns `TaskSubmitResponse`. | | OpenAPI binding | `x-iri-relation: ["https://iri.science/rels/read-file-head"]` on that Operation Object. | ## 2. Semantic Meaning The `iri:read-file-head` relationship advertises the operation entry point through which a client may request the beginning of files in the source Resource's configured filesystem context. File operands and read parameters remain in the OpenAPI-defined request body. The relation identifies an applicable read operation, not file content or a result representation. It does not grant authorization, prove that an identified path exists, or guarantee any particular content. ## 3. Source, Target, and Operation Context The relationship MAY originate only from a Resource whose exact `resource_type` is one of: ```text urn:doe-iri:resource:compute urn:doe-iri:resource:compute:system urn:doe-iri:resource:compute:node urn:doe-iri:resource:storage urn:doe-iri:resource:storage:filesystem urn:doe-iri:resource:storage:mount urn:doe-iri:resource:service:dtn ``` Eligibility is exact-type-based and is not inherited by other Resource Type descendants. For every eligible type, the adapter MUST establish the path namespace and one unambiguous execution/access context for the source Resource. Type classification, topology links, mount relationships, and `supported_endpoints` alone do not establish applicability. In particular, a mount does not inherit operations from its filesystem or consuming system, and a DTN's hosting or mount-access links do not imply a filesystem execution context. Generic compute and storage Resources are eligible only when their actual adapter semantics are known. If one source cannot identify an unambiguous context, the producer MUST expose separate Resources and use registered topology relations; it MUST NOT silently choose a host or add an undocumented context selector. The producer MUST bind `resource_id` to the represented Resource's adapter context. Because it is the only path variable, the advertised operation link is concrete rather than templated. If the operation belongs to a different Resource, the producer MUST expose the appropriate Resource relationship rather than advertise the operation as belonging to this source. When `supported_endpoints` is present on the source Resource, advertising `iri:read-file-head` requires `"filesystem"` in that array. The reverse implication does not apply, and authorization-suppressed omission does not make a retained `"filesystem"` category inconsistent. A representation advertising `iri:read-file-head` MUST also advertise at least one applicable `service-desc` link whose deployed OpenAPI description contains the binding in Section 8. The operation link MUST NOT carry an IRI representation `profile`. ## 4. Cardinality Each eligible Resource MAY advertise zero or one applicable operation entry point: ```text Resource -- iri:read-file-head --> File-head operation entry point 1 0..1 ``` The HAL relation uses a singular link object when supplied. ## 5. Asynchronous Invocation Semantics The mapped operation remains `POST` and returns `TaskSubmitResponse`. Following the relation submits asynchronous work; it does not synchronously return file content or a file representation. Clients use the existing Task monitoring flow and the governing OpenAPI contract to determine the outcome and interpret the result. This relation MUST NOT be treated as a direct-content link or an invented `GET` file operation. ## 6. Stability and Availability The relationship describes a configured applicable operation affordance. Its presence SHOULD remain stable across ordinary changes in load, health, reachability, or file contents. It may change when the facility configures or withdraws the adapter operation or changes visibility for the requester. The relation does not prove that the target is currently healthy, reachable, or available. Clients MUST handle ordinary invocation and Task failures. ## 7. Authorization, Visibility, and Omission Authorization MAY affect visibility of the operation affordance. A provider MAY omit `iri:read-file-head` when the requester is not authorized to discover or use the entry point. Presence grants no permission and guarantees no successful file read. Omission means only that the affordance is not advertised in this representation. It does not prove that file-head reading is unsupported everywhere or permanently unavailable. Links MUST NOT contain credentials or secrets. A client MUST NOT automatically forward credentials to an unrelated origin solely because an operation link or service description names it. ## 8. OpenAPI Contract and Binding The current operation mapping is: ```text POST /api/v2/filesystem/head/{resource_id} operationId: head success status: 200 success schema: TaskSubmitResponse x-iri-relation: ["https://iri.science/rels/read-file-head"] ``` OpenAPI remains authoritative for the bound path parameter, `PostHeadRequest` request body, responses, errors, Task submission, and security behavior. Clients MUST follow the advertised target and the applicable deployed OpenAPI description; they MUST NOT construct a URL or infer an HTTP method from the relation name. The canonical relation URI, rather than `operationId`, is the machine-readable binding key. ## 9. HAL Representation ```json { "id": "scratch", "resource_type": "urn:doe-iri:resource:storage:filesystem", "supported_endpoints": ["filesystem"], "_links": { "curies": [ { "name": "iri", "href": "https://iri.science/rels/{rel}", "templated": true } ], "iri:read-file-head": { "href": "https://api.example.org/api/v2/filesystem/head/scratch" }, "service-desc": { "href": "https://api.example.org/openapi.json", "type": "application/vnd.oai.openapi+json;version=3.1" } } } ``` ## 10. Governing Sources - [Resource operation-affordance RFC](https://github.com/doe-iri/iri-facility-api-docs/blob/76a4a0c8992429d0358e8309211cb30a4af1c83c/rfc/rfc-resource-operation-affordances.md) - [IRI v2 filesystem OpenAPI](https://github.com/doe-iri/iri-facility-api-docs/blob/76a4a0c8992429d0358e8309211cb30a4af1c83c/specification-v2/openapi/production/filesystem.yaml) - [Common Resource profile](/profiles/status/resource/) - [Compute-system Resource Definition Profile](/profiles/resource-definition/compute/system/) - [Compute-node Resource Definition Profile](/profiles/resource-definition/compute/node/) - [Filesystem Resource Definition Profile](/profiles/resource-definition/storage/filesystem/) - [Mount Resource Definition Profile](/profiles/resource-definition/storage/mount/) - [DTN service Resource Definition Profile](/profiles/resource-definition/service/dtn/) --- *DOE Integrated Research Infrastructure — Link Relation: read-file-head*