BCF to Nostr event mapping

Scope and design rules

The mapping targets BCF 3.0 first, with a BCF 2.1 import/export fallback. It is intentionally conservative: fields from BCF are preserved, unknown extension data is kept in JSON, and event relationships are expressed with Nostr's standard indexed tags where possible.

Nostr event IDs are derived from the signed event payload. That means the BCF GUID must not be treated as the event ID. The BCF GUID lives in d and bcf-guid; the Nostr id is the signature-derived hash.

Event family

Tag vocabulary

Use indexed single-letter tags for discovery, and verbose BCF tags for readability. Relays are expected to index single-letter tags such as a, e, p, d, s and t. Multi-letter tags are preserved but should be filtered client-side unless the relay explicitly indexes them.

BCF topic mapping

A BCF topic is the current issue state. It is addressable because BCF topics change: status, priority, assignee, due date and labels may be updated. The authoritative current state is the latest kind:30900 for the same d tag. For every meaningful update, emit a matching kind:1171 audit event.

{
  "kind": 30900,
  "pubkey": "<author-pubkey-hex>",
  "created_at": 1778946000,
  "tags": [
    ["d", "b345f4f2-3a04-b43b-a713-5e456bef8228"],
    ["a", "30902:<owner-pubkey>:pilot-2026"],
    ["bcf-guid", "b345f4f2-3a04-b43b-a713-5e456bef8228"],
    ["bcf-version", "3.0"],
    ["bcf-status", "Open"],
    ["s", "Open"],
    ["bcf-type", "Clash"],
    ["bcf-priority", "High"],
    ["bcf-stage", "LP4"],
    ["bcf-due", "1779577200"],
    ["bcf-server-assigned-id", "P-2026-042"],
    ["p", "<mep-pubkey>", "", "assignee"],
    ["p", "<structural-pubkey>", "", "consulted"],
    ["t", "mep"],
    ["t", "structure"],
    ["ifc", "2Y$0aBv19FqQ9rP5J6wQhA"],
    ["ifc-file", "<ifc-file-ref-event-id>"],
    ["e", "<viewpoint-event-id>", "", "viewpoint"],
    ["e", "<snapshot-file-event-id>", "", "snapshot"]
  ],
  "content": "{\"title\":\"Duct crosses main girder at axis 4/B\",\"description\":\"MEP duct intersects primary steel beam. Need reroute or structural opening decision.\",\"labels\":[\"mep\",\"structure\"],\"extensions\":{}}"
}

BCF comment mapping

BCF comments become regular immutable events. They reference the topic by event ID with an e tag and carry the original BCF comment GUID in content. If a tool imports an edited BCF comment, publish a new comment event with an e marker replaces; do not mutate the original signed event.

{
  "kind": 1170,
  "pubkey": "<structural-pubkey>",
  "created_at": 1778950200,
  "tags": [
    ["e", "<topic-event-id>", "", "root"],
    ["a", "30902:<owner-pubkey>:pilot-2026"],
    ["p", "<mep-pubkey>"],
    ["e", "<viewpoint-event-id>", "", "viewpoint"]
  ],
  "content": "{\"guid\":\"a333fca8-1a31-caac-a321-bb33abc8414\",\"topic_guid\":\"b345f4f2-3a04-b43b-a713-5e456bef8228\",\"text\":\"Girder HEB400 cannot be lowered. Please reroute duct below suspended ceiling zone.\",\"date\":\"2026-05-16T10:10:00Z\"}"
}

BCF viewpoint mapping

The viewpoint captures how to reopen the problem in a model viewer: camera, clipping, annotations, selected components, visible components, colors and optional bitmap/snapshot references. BCF API treats viewpoints as immutable; this profile follows that rule.

{
  "kind": 30901,
  "pubkey": "<author-pubkey-hex>",
  "created_at": 1778945700,
  "tags": [
    ["d", "a11a82e7-e66c-34b4-ada1-5846abf39133"],
    ["a", "30902:<owner-pubkey>:pilot-2026"],
    ["bcf-guid", "a11a82e7-e66c-34b4-ada1-5846abf39133"],
    ["bcf-version", "3.0"],
    ["ifc", "2Y$0aBv19FqQ9rP5J6wQhA"],
    ["ifc", "1hJ9K0lMn2OP3Q4rS5tUvW"],
    ["ifc-file", "<ifc-file-ref-event-id>"],
    ["e", "<snapshot-file-event-id>", "", "snapshot"]
  ],
  "content": "{\"guid\":\"a11a82e7-e66c-34b4-ada1-5846abf39133\",\"camera\":{\"type\":\"perspective\",\"camera_view_point\":{\"x\":12.4,\"y\":8.2,\"z\":3.1},\"camera_direction\":{\"x\":-0.8,\"y\":0.1,\"z\":-0.2},\"camera_up_vector\":{\"x\":0,\"y\":0,\"z\":1},\"field_of_view\":60,\"aspect_ratio\":1.77},\"components\":{\"selection\":[{\"ifc_guid\":\"2Y$0aBv19FqQ9rP5J6wQhA\"}],\"visibility\":{\"default_visibility\":true,\"exceptions\":[]}},\"clipping_planes\":[]}"
}

Worked example

The minimal useful BCF exchange is not one event. It is a small graph: file metadata for the snapshot, a viewpoint, the topic, then comments and audit records.

1. Snapshot file kind:1063

{
  "kind": 1063,
  "pubkey": "<author-pubkey-hex>",
  "created_at": 1778945600,
  "tags": [
    ["url", "https://blossom.example/files/snap-axis-4b.png"],
    ["m", "image/png"],
    ["x", "6f1e9d4a6f7b0a2c3d4e5f67890abcdeffedcba09876543210abcdef12345678"],
    ["size", "284102"],
    ["dim", "1440x900"],
    ["a", "30902:<owner-pubkey>:pilot-2026"],
    ["alt", "BCF snapshot showing duct crossing steel girder at axis 4/B"]
  ],
  "content": "Snapshot for topic P-2026-042"
}

2. Topic current state kind:30900

Use the topic example above. The important relationships are: e:viewpoint, e:snapshot, project a, assignee p, and status mirror s.

3. Status update audit kind:1171

{
  "kind": 1171,
  "pubkey": "<mep-pubkey>",
  "created_at": 1779032400,
  "tags": [
    ["e", "<topic-event-id>", "", "root"],
    ["a", "30902:<owner-pubkey>:pilot-2026"],
    ["audit-field", "bcf-status"],
    ["audit-from", "Open"],
    ["audit-to", "InProgress"],
    ["bcf-action", "update"],
    ["client", "bim-cvp-bcf-client/0.1"]
  ],
  "content": "{\"reason\":\"MEP team accepted the clash and is preparing reroute option.\"}"
}

4. Replacement topic state kind:30900

After the audit event, publish a new kind:30900 with the same d, same bcf-guid, updated bcf-status and updated s. Clients that only need the current state read this latest topic. Clients that need evidence read the 1171 chain.

Relay query patterns

These examples are Nostr filters. They are intentionally simple and assume the relay indexes single-letter tags as described in NIP-01.

All current BCF topics in one project

{
  "kinds": [30900],
  "#a": ["30902:<owner-pubkey>:pilot-2026"],
  "limit": 200
}

All open topics in one project

{
  "kinds": [30900],
  "#a": ["30902:<owner-pubkey>:pilot-2026"],
  "#s": ["Open"],
  "limit": 200
}

One topic thread

[
  {
    "kinds": [30900],
    "#d": ["b345f4f2-3a04-b43b-a713-5e456bef8228"],
    "limit": 1
  },
  {
    "kinds": [1170, 1171],
    "#e": ["<topic-event-id>"],
    "limit": 500
  }
]

All topics touching an IFC element

Standard NIP-01 relays should not be assumed to index multi-letter tags. The portable query fetches project topics and filters ifc tags client-side.

{
  "kinds": [30900, 30901],
  "#a": ["30902:<owner-pubkey>:pilot-2026"],
  "limit": 500
}

BCF XML/API round-trip rules

BCF-XML to Nostr

1. Read bcf.version, project.bcfp, extensions.xml and topic folders.
2. Create or update one kind:30902 project event containing extension lists.
3. For every snapshot or document file, publish kind:1063 with hash, MIME type, size and URL.
4. For every viewpoint file, publish one kind:30901; never republish the same viewpoint d.
5. For every topic, publish the current kind:30900 state using the original topic GUID.
6. For every comment, publish kind:1170 and preserve comment GUID, author/date and optional viewpoint reference.
7. If the source contains history, publish kind:1171 audit events; otherwise mark import provenance in content.

Nostr to BCF-XML

1. Resolve project kind:30902 and extension lists.
2. Resolve latest kind:30900 per topic d.
3. Resolve linked viewpoints and snapshots via e markers.
4. Sort comments by created_at, then by event ID for tie-breaking.
5. Write markup.bcf, viewpoint.bcfv, snapshot files and optional documents.xml.
6. Keep unknown content fields as BCF extension data where possible; otherwise write an export warning.

BCF API adapter

The API adapter maps REST mutations to signed events: POST Topic publishes 30900; PUT Topic publishes a new 30900 and a 1171; POST Comment publishes 1170; POST Viewpoint publishes 30901; BCF API event endpoints read from 1171.

Validation checklist

Sources

• buildingSMART BCF API 3.0 repository
• buildingSMART BCF XML repository
• buildingSMART BCF technical overview
• Nostr NIP-01 event and tag model
• Nostr NIP-94 file metadata