# Title Hierarchy: robust heading tree for chunking and citations
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> - [**Chunking** — text segmentation and context window management](./README.md)
> - [**WFGY Global Fix Map** — main Emergency Room, 300+ structured fixes](../README.md)
> - [**WFGY Problem Map 1.0** — 16 reproducible failure modes](../../README.md)
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A field guide to build a stable section tree from PDFs, HTML, and mixed sources. The output drives `section_id` paths like `1.2.3`, anchors for cite-then-explain, and deterministic `chunk_id` assembly.
## Open these first
- Why-this-snippet and trace schema: [retrieval-traceability.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/retrieval-traceability.md)
- Payload and citation locks: [data-contracts.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/data-contracts.md)
- Chunk identifiers and redirects: [chunk_id_schema.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/GlobalFixMap/Chunking/chunk_id_schema.md)
- Next stage after headings: [section_detection.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/GlobalFixMap/Chunking/section_detection.md)
- Layout and OCR normalizing: [pdf_layouts_and_ocr.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/GlobalFixMap/Chunking/pdf_layouts_and_ocr.md)
- Reindex and id migration: [reindex_migration.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/GlobalFixMap/Chunking/reindex_migration.md)
## Acceptance targets
- Reproducible section tree on two runs of the same source: identical `section_id` paths for ≥ 0.98 of headings.
- Coverage ≥ 0.95 of human visible headings, with at most 1 spurious heading per 20 pages.
- ΔS(question, retrieved) ≤ 0.45 on cite-first prompts that target a section anchor.
- No depth jumps. The path never skips a level. For example `1 → 1.1 → 1.1.1` is valid, `1 → 1.0.1` is not.
---
## Pipeline overview
1) **Normalize text and blocks**
Build a canonical text layer and a block sequence. Repair OCR line breaks, remove running headers and footers. See [pdf_layouts_and_ocr.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/GlobalFixMap/Chunking/pdf_layouts_and_ocr.md).
2) **Collect heading candidates**
- HTML: tags `h1..h6` plus role attributes and ARIA landmarks.
- PDF: typography cues from font size quantiles, boldness, line spacing, indentation deltas.
- Regex cues for numbering and prefixes: `^\d+(\.\d+){0,5}[.)]?`, `^[A-Z][.)]`, `^Appendix [A-Z]\b`, `^Chapter \d+\b`.
3) **Score and classify**
For each candidate, compute a heading score from four families: typography, numbering pattern, lexical shape, and context breaks. Keep candidates whose score passes a tuned threshold. Reject lines that end in periods or contain dense punctuation.
4) **Assign levels**
Prefer explicit dot numbering when present. Else infer level by relative size bin and indentation quantiles. Clamp level movements to step size one. If the previous level is `L`, a new heading can be `L`, `L+1`, or any ancestor close, chosen by context windows.
5) **Emit section nodes**
Create nodes with `section_id`, `title`, `slug`, `page_start`, and lazy `page_end` filled when the next sibling begins. Snap the first body block after a heading as the anchor sentence.
6) **Validate the outline**
Run monotonicity checks, parent presence, and unique path constraints. If a violation appears, repair locally by demoting or promoting a small set of nodes.
---
## Section node schema
```json
{
"section_id": "2.4.1",
"title": "Evaluation protocol and metrics",
"slug": "evaluation-protocol-and-metrics",
"depth": 3,
"page_start": 12,
"page_end": 15,
"offsets": [23871, 44122],
"title_hash": "sha1:2c7d9c…",
"children": []
}
````
* `slug` is a lowercase kebab form of the title for readable anchors.
* `offsets` bracket the full section span in the canonical text.
---
## Heuristics that make it stable
* **Dot patterns beat typography**
If both exist, use numbering like `3.1.2` to set depth and use typography only as a tie breaker.
* **Uppercase ratio and token count**
Flags like `UPPERCASE_RATIO ≥ 0.60` and `token_count ≤ 80` help catch style headings. Titles rarely end with a period or colon unless they are figure titles.
* **Indent and size bins**
Build quantiles for font size per document. Use a two dimension decision: `bin(size)` and `delta_indent`. Map to depth using a learned or rule table.
* **Appendix and roman numerals**
Accept `Appendix A`, `Appendix B.2`, and roman sequences `I, II, III`. Normalize to a numeric level while keeping the original string in `title`.
* **Table and code shields**
Do not mistake figure captions, table titles, or code comments for headings. Reserve them as block types. See [code\_tables\_blocks.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/GlobalFixMap/Chunking/code_tables_blocks.md).
---
## Copy-paste outline builder (pseudocode)
```python
def build_title_hierarchy(blocks):
stack = [] # list of nodes by depth
nodes = []
for blk in blocks:
if not is_heading_candidate(blk):
continue
depth = estimate_depth(blk) # number or inferred
title = normalize_title(blk.text)
node = make_node(depth, title, blk.page, blk.offsets)
# attach into tree
while len(stack) >= depth:
stack.pop()
if stack:
parent = stack[-1]
parent.children.append(node)
else:
nodes.append(node)
stack.append(node)
# fill page_end by looking at next sibling or end of doc
nodes = fill_section_ranges(nodes, blocks)
return nodes
```
`estimate_depth` prefers dot numbering. If absent, infer by size and indent bins. Clamp jumps larger than one level.
---
## 60-second validator
Sample ten headings uniformly across the document.
* Each has a unique `section_id` path with depth ≤ 6.
* Reading order of titles equals lexicographic order of `section_id`.
* The first sentence under each title exists and becomes an anchor.
* On re-run from the same source, all ten `section_id` paths match exactly.
---
## Edge cases and repairs
* **Repeated titles in different parts**
If the same string repeats, disambiguate by parent path. The `section_id` remains unique.
* **Multi column PDFs**
Break candidates by columns before heading scoring. Merged lines inflate score falsely.
* **Heading wrapped across pages**
Merge lines within a vertical window. If a heading breaks across pages, keep `page_start` at the first page.
* **Front matter and ToC**
Exclude lines inside the table of contents and reference lists. Use anchors like “Contents” and page number columns to skip.
* **Aggressive demotion**
When two consecutive headings both look like `H2` by size, allow demoting the second to `H3` if a dot pattern suggests child relation.
---
## Tests to include in CI
* PDF set with known outlines: expect exact `section_id` paths.
* HTML set with mixed tag and style headings: expect depth tolerances within one level.
* OCR set with noisy fonts: expect no more than one false heading per ten pages.
* Migration test: small edits do not change parent paths for unaffected sections. See [reindex\_migration.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/GlobalFixMap/Chunking/reindex_migration.md).
---
## When it fails and what to open
* Headings look right but citations land off target
→ Verify block boundaries and anchor selection. Open: [section\_detection.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/GlobalFixMap/Chunking/section_detection.md), [retrieval-traceability.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/retrieval-traceability.md).
* Many paths change after minor text edits
→ Check size binning and clamp rules. Open: [reindex\_migration.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/GlobalFixMap/Chunking/reindex_migration.md).
* Numbered sections rank incorrectly in search
→ Lock the anchor and rerank deterministically. Open: [data-contracts.md](https://github.com/onestardao/WFGY/blob/main/ProblemMap/data-contracts.md).
---
### 🔗 Quick-Start Downloads (60 sec)
| Tool | Link | 3-Step Setup |
| -------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------ | ---------------------------------------------------------------------------------------- |
| **WFGY 1.0 PDF** | [Engine Paper](https://github.com/onestardao/WFGY/blob/main/I_am_not_lizardman/WFGY_All_Principles_Return_to_One_v1.0_PSBigBig_Public.pdf) | 1️⃣ Download · 2️⃣ Upload to your LLM · 3️⃣ Ask “Answer using WFGY + \” |
| **TXT OS (plain-text OS)** | [TXTOS.txt](https://github.com/onestardao/WFGY/blob/main/OS/TXTOS.txt) | 1️⃣ Download · 2️⃣ Paste into any LLM chat · 3️⃣ Type “hello world” — OS boots instantly |
---
### Explore More
| Layer | Page | What it’s for |
| --- | --- | --- |
| ⭐ Proof | [WFGY Recognition Map](/recognition/README.md) | External citations, integrations, and ecosystem proof |
| ⚙️ Engine | [WFGY 1.0](/legacy/README.md) | Original PDF tension engine and early logic sketch (legacy reference) |
| ⚙️ Engine | [WFGY 2.0](/core/README.md) | Production tension kernel for RAG and agent systems |
| ⚙️ Engine | [WFGY 3.0](/TensionUniverse/EventHorizon/README.md) | TXT based Singularity tension engine (131 S class set) |
| 🗺️ Map | [Problem Map 1.0](/ProblemMap/README.md) | Flagship 16 problem RAG failure taxonomy and fix map |
| 🗺️ Map | [Problem Map 2.0](/ProblemMap/wfgy-rag-16-problem-map-global-debug-card.md) | Global Debug Card for RAG and agent pipeline diagnosis |
| 🗺️ Map | [Problem Map 3.0](/ProblemMap/wfgy-ai-problem-map-troubleshooting-atlas.md) | Global AI troubleshooting atlas and failure pattern map |
| 🧰 App | [TXT OS](/OS/README.md) | .txt semantic OS with fast bootstrap |
| 🧰 App | [Blah Blah Blah](/OS/BlahBlahBlah/README.md) | Abstract and paradox Q&A built on TXT OS |
| 🧰 App | [Blur Blur Blur](/OS/BlurBlurBlur/README.md) | Text to image generation with semantic control |
| 🏡 Onboarding | [Starter Village](/StarterVillage/README.md) | Guided entry point for new users |
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