How to Classify PDF Tables by Their Borders (and Why It Matters): LATTICE vs STREAM

TLDR

PDF tables fall into two distinct architectural classes: LATTICE_TABLE (explicit vector grid lines) and STREAM_TABLE (borderless column alignment implied by text $X$-coordinates). Running standard grid cell expansion (colspan/rowspan) on borderless stream tables collapses all cells into a single full-page spanning cell. Setting isBorderless = true disables expansion loops, while distinct CSS wrapper classes (.pdf-table--lattice vs .pdf-table--borderless) preserve semantic rendering.

Table Architecture	Detection Evidence	Grid Line Input	colspan/rowspan Expansion	CSS Styling Class
LATTICE_TABLE	Vector Path Segments	$H/V$ Grid Lines	Enabled (Full expansion)	.pdf-table--lattice (Borders)
STREAM_TABLE	Spatial $X$-Clustering	hLines: [], vLines: []	Disabled (isBorderless = true)	.pdf-table--borderless (Clean)

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Technical implementation & overlap guard

// Table Builder: Disable colspan/rowspan expansion for borderless stream tables
export function buildTableHtmlGrid(latticeGridData) {
  const isBorderless = latticeGridData.hLines.length === 0 && latticeGridData.vLines.length === 0;
if (isBorderless) {     // Stream tables skip expansion logic: assign explicit 1x1 cells     return renderBorderlessTableHtml(latticeGridData.cells);   }
// Lattice tables execute full grid expansion   return renderLatticeTableHtml(expandCellSpans(latticeGridData)); }
// Overlap Guard: Prefer physical vector lattice tables over stream heuristics export function resolveTableClassification(latticeTables, streamTables) {   const finalTables = [...latticeTables];
for (const streamTable of streamTables) {     const overlapCoverage = calculateItemCoverage(streamTable, latticeTables);     // Skip stream table if 80%+ of items are already claimed by a physical lattice grid     if (overlapCoverage > 0.8) continue;     finalTables.push(streamTable);   }
return finalTables; }

Rule of thumb: Disable colspan/rowspan expansion for borderless stream tables (isBorderless = true) and prioritize vector lattice grids when classifications overlap.