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+# Dataset Design
+
+## Schema
+
+Every entry in the Scandium Dataset follows this schema:
+
+```python
+{
+    # Identity
+    "source": str,            # "mp", "oqmd", or "jarvis"
+    "source_id": str,         # Original database ID
+    "formula": str,           # Reduced formula
+    
+    # Properties
+    "formation_energy_per_atom": float,   # eV/atom
+    "energy_above_hull": float,           # eV/atom (null for JARVIS)
+    "band_gap": float,                    # eV
+    
+    # Structure
+    "structure_json": str,    # JSON-encoded pymatgen Structure
+    "nsites": int,
+    "volume": float,          # ų
+    "density": float,         # g/cm³
+    "space_group": int,       # International number
+    "space_group_symbol": str,
+    
+    # Composition
+    "elements": [str],        # Element list (with repetitions)
+    "anions": [str],          # Anion elements
+    
+    # Classification
+    "families": [str],        # Material families
+    "carrier_elements": [str], # Mobile ions (Li, Na, etc.)
+    "is_metal": bool,
+    "magnetic_ordering": str or None,
+    "is_experimental": bool,
+    
+    # Quality
+    "quality_score": float,   # 0-100 composite
+    "quality_sub_scores": {
+        "geometry": int,      # 0-25
+        "dft": int,           # 0-20
+        "metadata": int,      # 0-15
+        "novelty": int,       # 0-20
+        "chemical": int       # 0-15 (yes, sums to 95 not 100)
+    },
+    "quality_flags": [str],
+    
+    # Tiering
+    "tier": str,              # "gold", "validated", "raw"
+    "tier_gates": {str: bool},
+    "strict_gold": {
+        "is_strict_gold": bool,
+        "gates": {str: bool},
+        "confidence_calibration": {...}
+    },
+    
+    # Provenance
+    "provenance": {
+        "source": str,
+        "source_id": str,
+        "checksum": str,
+        "repairs_applied": [dict],
+        "dedup_resolution": dict or None,
+        "tier_assignment": dict,
+        "version": str
+    },
+    
+    # Dedup
+    "duplicate_group": int or None,
+    
+    # References
+    "references": [str],
+    "source_weight": float,   # 1.0 for all entries
+}
+```
+
+## Source Integration
+
+### Materials Project (MP)
+- **API**: pymatgen MPRester
+- **Filter**: `chemsys` includes Li, Na, Mg, Ca, Zn, Al, K
+- **Completeness**: 100% for all metadata fields
+- **Count**: 69,279 entries
+
+### OQMD
+- **API**: jarvis-tools `data("oqmd_3d_no_cfid")`
+- **Count**: 171,780 entries
+- **Known issues**: All resolved via repair pipeline
+
+### JARVIS-DFT
+- **API**: jarvis-tools `data("jarvis_dft_3d")`
+- **Count**: 25,673 entries
+- **Limitation**: No energy_above_hull (fundamental)
+
+## Family Classification
+
+Each entry is classified into one or more material families based on
+element composition:
+
+| Family | Criteria | Battery Relevance |
+|--------|----------|------------------|
+| intermetallic | No O, S, F, Cl, Br, I | Low |
+| layered_oxide | Has O + Li/Na + transition metal | High |
+| sulfide_sse | Has S + Li/Na | Critical |
+| halide_sse | Has F/Cl/Br/I + Li/Na | Critical |
+| polyanion | Has O + P/S + Li/Na | High |
+| nasicon | Na/Zr/Si/P pattern | Critical |
+| garnet | Li/La/Zr pattern | Critical |
+| borohydride | Has B + H + Li/Na | Medium |
+| oxide | Has O, not otherwise classified | Medium |
+
+## Three Editions
+
+| Edition | Scope | Entries |
+|---------|-------|---------|
+| General | All entries | 266,732 |
+| Battery | Battery families only | 82,925 |
+| Electrolyte | Strict Gold, battery, no OQMD | 41,665 |