diff --git a/app/Http/Controllers/TableEditController.php b/app/Http/Controllers/TableEditController.php
index f4dbc79..6a09a6d 100644
--- a/app/Http/Controllers/TableEditController.php
+++ b/app/Http/Controllers/TableEditController.php
@@ -11,6 +11,9 @@ use Illuminate\Support\Facades\Input;
 use MightyPork\Exceptions\SimpleValidationException;
 use MightyPork\Utils\Utils;
 
+/**
+ * Draft composing
+ */
 class TableEditController extends Controller
 {
     /**
diff --git a/app/Tables/Changeset.php b/app/Tables/Changeset.php
index e9fb694..d68dedd 100644
--- a/app/Tables/Changeset.php
+++ b/app/Tables/Changeset.php
@@ -6,7 +6,6 @@ namespace App\Tables;
 use App\Models\Revision;
 use App\Models\Row;
 use App\Models\Table;
-use Illuminate\Pagination\Paginator;
 use Illuminate\Queue\SerializesModels;
 use Illuminate\Support\Collection;
 use MightyPork\Exceptions\NotApplicableException;
@@ -105,6 +104,12 @@ class Changeset
      */
     public $removedColumns = [];
 
+    /**
+     * Generator iterating all properties, used internally for serialization to array
+     *
+     * @return \Generator
+     * @throws \ReflectionException
+     */
     private function walkProps()
     {
         $properties = (new ReflectionClass($this))->getProperties();
@@ -299,6 +304,8 @@ class Changeset
     }
 
     /**
+     * Retrieve a column by ID (even new columns)
+     *
      * @param string $id
      * @return Column
      */
@@ -315,7 +322,9 @@ class Changeset
     }
 
     /**
-     * @param string $id
+     * Retrieve a column and modify it by the Changeset.
+     *
+     * @param string $id - column ID
      * @return Column
      */
     public function fetchAndTransformColumn(string $id)
@@ -333,6 +342,11 @@ class Changeset
         return $column;
     }
 
+    /**
+     * Mark a row for removal
+     *
+     * @param int $id - row ID (_id)
+     */
     public function rowRemove(int $id)
     {
         if ($this->isNewRow($id)) {
@@ -343,21 +357,44 @@ class Changeset
         }
     }
 
+    /**
+     * Undo row removal
+     *
+     * @param int $id - row ID (_id)
+     */
     public function rowRestore(int $id)
     {
         $this->removedRows = array_diff($this->removedRows, [$id]);
     }
 
+    /**
+     * Test if a row is new
+     *
+     * @param int $id - row ID (_id)
+     * @return bool - is new
+     */
     public function isNewRow(int $id)
     {
         return isset($this->newRows[$id]);
     }
 
+    /**
+     * Test if a column is new
+     *
+     * @param string $id - column ID
+     * @return bool - is new
+     */
     public function isNewColumn(string $id)
     {
         return isset($this->newColumns[$id]);
     }
 
+    /**
+     * Retrieve a single row and transform it by the Changeset
+     *
+     * @param int $id - row ID (_id)
+     * @return \DecoratedRow|object
+     */
     public function fetchAndTransformRow(int $id)
     {
         $r = $this->fetchRow($id);
@@ -365,7 +402,12 @@ class Changeset
         return $transformed;
     }
 
-    public function fetchColumns()
+    /**
+     * Fetch columns from DB (not including new columns)
+     *
+     * @return Column[]
+     */
+    public function fetchRevisionColumns()
     {
         return Column::columnsFromJson($this->revision->columns);
     }
@@ -384,7 +426,7 @@ class Changeset
             return $nr;
         }
 
-        $r = $this->revision->rowsData($this->fetchColumns(), true, false)
+        $r = $this->revision->rowsData($this->fetchRevisionColumns(), true, false)
             ->whereRaw("data->>'_id' = ?", $id)->first();
 
         if (!$r) throw new NotExistException("No such row _id = $id in this revision.");
@@ -443,8 +485,10 @@ class Changeset
     }
 
     /**
-     * @param $newVals
-     * @return Column
+     * Update a column specification
+     *
+     * @param object $newVals - new values for the column
+     * @return Column - the column, modified and decorated with _orig etc
      */
     public function columnUpdate($newVals)
     {
@@ -475,6 +519,11 @@ class Changeset
         return $this->fetchAndTransformColumn($id);
     }
 
+    /**
+     * Mark a column for removal, or forget it if it's a new column
+     *
+     * @param string $id - column ID
+     */
     public function columnRemove(string $id)
     {
         if ($this->isNewColumn($id)) {
@@ -489,13 +538,18 @@ class Changeset
         $this->clearColumnOrderIfUnchanged();
     }
 
+    /**
+     * Restore a column previously marked for removal
+     *
+     * @param string $id - column ID
+     */
     public function columnRestore(string $id)
     {
         $this->removedColumns = array_diff($this->removedColumns, [$id]);
     }
 
     /**
-     * Get a page of added rows for display in the editor
+     * Get a page of new rows, for display in the editor
      *
      * @param int $perPage
      * @return \Illuminate\Pagination\LengthAwarePaginator|Collection|array
@@ -506,14 +560,18 @@ class Changeset
     }
 
     /**
-     * @param Column[] $columns
-     * @param array $csvArray
-     * @param bool $forTableInsert
-     * @return \array[][]|Collection
+     * Convert a raw CSV array to a rows array, validating and casting the data.
+     * All created rows are assigned globally unique IDs
+     *
+     * @param Column[] $columns - ordered array of columns to collect from all CSV rows
+     * @param array $csvArray - CSV parsed to 2D array
+     * @param bool $forTableInsert - if true, row data will be wrapped in ['data'=>...]
+     *                               so it can be inserted directly into DB
+     * @return Collection
      */
     public static function csvToRowsArray($columns, $csvArray, $forTableInsert)
     {
-        /** @var Collection|array[][] $rows */
+        /** @var Collection $rows */
         $rows = collect($csvArray)->map(function ($row) use ($columns, $forTableInsert) {
             if (count($row) == 0 || count($row) == 1 && $row[0] == '') return null; // discard empty lines
             if (count($row) != count($columns)) {
@@ -539,7 +597,8 @@ class Changeset
             }
         })->filter();
 
-
+        // TODO we could use some temporary IDs and replace them with
+        // TODO   proper unique IDs when submitting the proposal
         $rowNumerator = new RowNumerator(count($csvArray));
 
         if ($forTableInsert) {
@@ -556,16 +615,23 @@ class Changeset
         }
     }
 
+    /**
+     * Append N blank rows
+     *
+     * @param int $count
+     */
     public function addBlankRows(int $count)
     {
-        $numerator = new RowNumerator($count);
-
         $columns = $this->fetchAndTransformColumns();
         $template = [];
         foreach ($columns as $column) {
             $template[$column->id] = $column->cast(null);
         }
 
+        // TODO we could use some temporary IDs and replace them with
+        // TODO   proper unique IDs when submitting the proposal
+        $numerator = new RowNumerator($count);
+
         foreach ($numerator->generate() as $_id) {
             $row = $template;
             $row['_id'] = $_id;
@@ -573,6 +639,11 @@ class Changeset
         }
     }
 
+    /**
+     * Add rows from imported CSV
+     *
+     * @param array $csvArray - CSV parsed to 2D array
+     */
     public function addFilledRows($csvArray)
     {
         /** @var Column[] $columns */
@@ -585,6 +656,11 @@ class Changeset
         $this->newRows = $this->newRows + $rows->toArray();
     }
 
+    /**
+     * Add a blank column (pre-filled with dummies to satisfy validation)
+     *
+     * @return array - column array
+     */
     public function addBlankCol()
     {
         $cid = (new ColumnNumerator(1))->next();
@@ -604,6 +680,11 @@ class Changeset
         return $col;
     }
 
+    /**
+     * Set a new column order
+     *
+     * @param array $order - array of column IDs
+     */
     public function setColOrder(array $order)
     {
         $allCols = $this->fetchAndTransformColumns();
@@ -615,9 +696,12 @@ class Changeset
         $this->clearColumnOrderIfUnchanged();
     }
 
+    /**
+     * Remove added rows that are not filled (user added too many with the Add Rows form)
+     */
     public function removeEmptyNewRows()
     {
-        $cols = $this->fetchColumns();
+        $cols = $this->fetchRevisionColumns();
         $emptyTpl = collect($cols)->keyBy('id')->map(function(Column $c) {
             return $c->cast(null);
         })->all();
@@ -638,6 +722,10 @@ class Changeset
         });
     }
 
+    /**
+     * Discard the column order array if it's identical to the natural / default
+     * ordering. This simplifies the Changeset and reduces possible conflicts
+     */
     public function clearColumnOrderIfUnchanged()
     {
         $expected = collect($this->revision->columns)
@@ -653,16 +741,25 @@ class Changeset
         }
     }
 
+    /**
+     * Clear the custom column order
+     */
     public function resetColumnOrder()
     {
         $this->columnOrder = [];
     }
 
+    /**
+     * Restore all columns marked for removal
+     */
     public function resetRemovedColumns()
     {
         $this->removedColumns = [];
     }
 
+    /**
+     * Discard all added columns
+     */
     public function resetAddedColumns()
     {
         $this->columnOrder = array_values(
@@ -675,21 +772,33 @@ class Changeset
         $this->clearColumnOrderIfUnchanged();
     }
 
+    /**
+     * Discard all column changes
+     */
     public function resetUpdatedColumns()
     {
         $this->columnUpdates = [];
     }
 
+    /**
+     * Restore all rows marked for removal
+     */
     public function resetRemovedRows()
     {
         $this->removedRows = [];
     }
 
+    /**
+     * Discard all added rows
+     */
     public function resetAddedRows()
     {
         $this->newRows = [];
     }
 
+    /**
+     * Discard all row changes
+     */
     public function resetUpdatedRows()
     {
         $this->rowUpdates = [];