Clarify dataset description, methods and limitations

README.md

@@ -1,6 +1,6 @@
 ---
 license: odc-by
-pretty_name: "Whether L2 sequencers keep the inclusion promises they make"
+pretty_name: "OP Stack unsafe-head observations and canonical-chain checks"
 tags:
   - layer-2
   - rollup
@@ -15,48 +15,37 @@ size_categories:
   - 100K<n<1M
 ---
 
-# L2 sequencer preconfirmation reliability
+# L2 sequencer preconfirmation observations
 
-A rollup sequencer tells you your transaction is included before anything is settled on L1. This
-records whether that promise held.
-
-The promise is the ephemeral part. If a sequencer replaces an unsafe block, the version it
-originally gossiped is discarded and no archive serves it, so a broken promise is only
-observable to somebody who wrote down the original.
+Periodic observations of unsafe and safe heads on selected OP Stack networks, with subsequent checks of sampled unsafe block hashes against the chain reported by the endpoint. The panel records coverage and detected changes to previously observed blocks.
 
 ## Contents
 
-| name | one row is |
+| Table | Record |
 |---|---|
-| `e14_l2_preconf` | either a heartbeat, recording how far the unsafe head ran ahead of the safe head, or a violation |
+| `e14_l2_preconf` | A heartbeat with head and check statistics, or a detected violation |
+
+## Using the data
+
+`row_type` separates heartbeats from violations. Use `n_checked` and `n_failed` to assess how many checks completed before interpreting a period with no detected violations.
+
+`lag_blocks` measures the reported gap between unsafe and safe heads. Use it only where `safe_tag_plausible` is true. Some endpoints have returned stale or inconsistent safe tags, which can produce implausibly large lags.
 
-## Mostly an attested absence
+Compare lag with each chain's own history. Different sequencer and batch-publication policies can produce different normal levels across networks.
 
-Violations are rare, and the value here is in the zeros being credible rather than in the
-events. That requires the coverage rows: `n_checked` counts promises actually verified against
-the canonical chain and `n_failed` counts the checks that could not complete. A run with no
-violations and no checks is not the same as a run with no violations and thousands.
+## Limitations
 
-`row_type` separates heartbeats from violations.
+- The configured coverage includes nine OP Stack chains. Results do not establish behaviour across other rollup architectures.
+- Sampling can miss a block that is proposed and replaced between observations.
+- Observations depend on public endpoint responses. A mismatch warrants investigation and is not, by itself, proof of a sequencer failure or an L1 finality failure.
+- An unsafe head is an early chain view, not a universal transaction-level confirmation guarantee.
+- No detected violations means none were found in completed checks; it does not establish uninterrupted reliability outside those checks.
 
-## Before you build on this
+## Files and access
 
-- `lag_blocks` is only meaningful where `safe_tag_plausible` is true. One chain's endpoint has
-  served a stale safe tag intermittently, giving a lag of tens of millions of blocks against
-  another chain's few dozen, then recovering to a normal figure hours later. It is kept rather
-  than dropped, because an endpoint's own inconsistency is a fact about running on public
-  infrastructure, and because it comes and goes you cannot exclude a chain once and be done.
-  The flag is false on exactly the affected rows; filter on it, not on the chain name.
-- The unsafe head is sampled every few seconds, so a block that was proposed and replaced between
-  two samples is invisible. This undercounts violations and cannot overcount them.
-- Nine chains, ALL OP-stack. That is nine independent sequencer operators, which is enough to
-  compare them against each other, but it is still one rollup architecture: nothing here
-  generalises to a rollup built differently.
-- Safe-head lag varies enormously between them even at rest, from tens of blocks to several
-  thousand, and one endpoint reports a lag of tens of millions. Compare a chain against its own
-  history rather than against another chain's absolute level.
+Data is stored as Parquet files under `dataset/YYYY/MM/`, with partitions for collection windows. Each measurement table has a fixed 7-day sample beginning at its configured collection start date. The sample windows in this repository span 2026-08-26 to 2026-09-01. Availability within each window depends on successful collection. The public sample dates remain fixed as additional history accumulates privately. Contact DataForge through the discussions tab to enquire about additional history.
 
-Partitions are parquet, one file per collection window, under `dataset/YYYY/MM/`. Every dataset here carries a FIXED 7-day sample WINDOW starting at its own first day of collection, together spanning 2026-08-26 to 2026-09-01, so you can check schema, coverage and quality before asking for more. It does not advance, so there is nothing to gain by re-downloading it. The full history is held privately, available on request.
+### Load a table
 
 ```python
 from huggingface_hub import snapshot_download
@@ -70,11 +59,8 @@ df = pd.concat(map(pd.read_parquet,
 
 ## Coverage
 
-`e0_run_manifest` lists every collection window with its poll counts and failure counts, and is
-published in full rather than windowed. Gaps between windows are real, cannot be filled in
-afterwards, and nothing here is interpolated.
+`e0_run_manifest` records collection windows, poll counts and failures. It is published in full and may cover dates beyond the fixed data sample. Collection gaps are not interpolated. Use the manifest together with table timestamps and error fields to assess coverage.
 
 ## License and contact
 
-ODC-BY: use it freely, credit "DataForge (dataforge-labs)". Questions and requests for the full
-history via the discussions tab.
+The public sample is published under ODC-BY. Attribute it to "DataForge (dataforge-labs)". For questions about the data or access to additional history, open a discussion in this repository.