Turing's Second Example

Turing's second example printed as a real machine: it lays down 0 1 0 11 0 111 … by treating the tape as scratch space. Seven control states sweep right to the working end, copy the previous block of 1s using an erasable marker symbol, append one more 1, and sweep back to start the next block. The tape is a self-growing chain of Cell entities over the symbols { blank, 0, 1, marker }, and a single Head carries the control state.

A step up from the first example: real computation that reads, writes and re-reads the tape rather than printing blindly. It shows the modelling pattern coping with a two-directional working region — the head sweeps both ways, leaves and clears markers, and uses the blank background as a boundary — all on a tape that still extends itself one cell at a time as the blocks grow.

# turing-second-example.osi.yaml — emitted automatically
semantic_model:
  name: "turing-second-example"
  source: "duckdb://turing-second-example.db"
  entities:
    - name: cell
      primary_key: id
  dimensions:
    - name: state
      type: categorical
    - name: t
      type: time
  measures:
    - name: row_count
      agg: count
    - name: active
      agg: sum
      filter: "state = 'ACTIVE'"