generated: '2026-07-20'
method: derived
source:
  - openapi/blockchalk-chalks-openapi.yml
  - examples/blockchalk-chalks-v0.6-georss-san-francisco.xml
  - examples/blockchalk-chalks-v0.6-georss-new-york.xml
name: BlockChalk data model
status: retired
summary: >-
  BlockChalk exposed a single public entity: the chalk, a short message pinned to a
  geographic point. The published read interfaces returned a flat feed of chalks with no
  nested or referenced sub-resources, so the entity graph is intentionally shallow.
entities:
  - name: Chalk
    description: A short public message pinned to a latitude/longitude, authored anonymously.
    identifier:
      field: guid
      format: >-
        Permalink URL whose final path segment is a 12-character lowercase hexadecimal
        identifier, e.g. http://blockchalk.com/d7788df3e7b8
      id_prefix: null
    fields:
      - name: title
        type: string
        description: The chalk body text as posted.
      - name: link
        type: uri
        description: Permalink to the chalk on blockchalk.com.
      - name: guid
        type: uri
        description: Unique identifier; observed identical to link.
      - name: pubDate
        type: string
        description: RFC 1123 timestamp of when the chalk was posted.
      - name: description
        type: string
        description: Human-readable proximity or neighborhood label relative to the query point.
      - name: georss:point
        type: string
        description: Space-separated latitude and longitude of the chalk.
    relationships: []
  - name: Location
    description: >-
      An implicit query-time entity rather than a stored resource. The caller supplies a
      latitude/longitude and the service resolves it to a proximity band and, where known, a
      named neighborhood that it echoes back in each chalk's description.
    identifier:
      field: coordinates
      format: 'latitude,longitude decimal degrees'
    fields:
      - name: latitude
        type: number
      - name: longitude
        type: number
    relationships:
      - type: has_many
        target: Chalk
        via: coordinates
        description: A queried location returns the chalks posted near it.
observed_conventions:
  proximity_bands:
    - right here
    - on this block
    - within a few blocks
  neighborhood_labels_observed:
    - in South of Market
    - in Lower Nob Hill
  message_prefixes_observed:
    description: >-
      Users adopted informal leading tags to categorize chalks. These were a social
      convention in the title text, not a structured field.
    values:
      - 'LAME'
      - 'NICE:'
      - 'FOR SALE:'
      - 'EVENT:'
      - '311:'
notes: >-
  No user, account, neighborhood or thread entity was ever exposed publicly, and no write
  surface was documented, so there are no ownership or authorship relationships to record.