diff --git a/pixelocr/gui/glyphdbedit.py b/pixelocr/gui/glyphdbedit.py
index b3ee04b..ea6e5ad 100644
--- a/pixelocr/gui/glyphdbedit.py
+++ b/pixelocr/gui/glyphdbedit.py
@@ -32,7 +32,44 @@ from ..glyphdb import GlyphDB
 from ..image import Image
 
 
+class Column(object):
+    header = None
+    def data(self, value):
+        return None
+
+    def image(self, value):
+        return None
+
+    def sortKey(self, value):
+        return self.data(value)
+
+
+class TextColumn(Column):
+    header = 'Text'
+
+    def data(self, value):
+        return value.text
+
+    def image(self, value):
+        return value.image.qimage
+
+
+class ElevationColumn(Column):
+    header = 'Elevation'
+
+    def data(self, value):
+        return str(value.elevation)
+
+    def sortKey(self, value):
+        return value.elevation
+
+
 class GlyphDBModel(QAbstractTableModel):
+    COLUMNS = [
+        TextColumn(),
+        ElevationColumn(),
+    ]
+
     def __init__(self, glyphdb, parent=None):
         super().__init__(parent)
         self.glyphdb = glyphdb
@@ -43,26 +80,19 @@ class GlyphDBModel(QAbstractTableModel):
         return len(self.values)
 
     def columnCount(self, parent):
-        return 2
+        return len(self.COLUMNS)
 
     def headerData(self, section, orientation, role):
-        if orientation != Qt.Horizontal or role != Qt.DisplayRole:
-            return None
-        if section == 0:
-            return 'Text'
-        elif section == 1:
-            return 'Elevation'
+        if orientation == Qt.Horizontal and role == Qt.DisplayRole:
+            return self.COLUMNS[section].header
 
     def data(self, index, role):
+        column = self.COLUMNS[index.column()]
         data = self.values[index.row()]
-        if index.column() == 0:
-            if role == Qt.DisplayRole:
-                return data.text
-            elif role == Qt.DecorationRole:
-                return data.image.qimage
-        elif index.column() == 1:
-            if role == Qt.DisplayRole:
-                return str(data.elevation)
+        if role == Qt.DisplayRole:
+            return column.data(data)
+        elif role == Qt.DecorationRole:
+            return column.image(data)
 
     def removeRows(self, row, count, parent=None):
         self.beginRemoveRows(parent, row, row + count - 1)
@@ -75,18 +105,11 @@ class GlyphDBModel(QAbstractTableModel):
         self.endRemoveRows()
         return True
 
-    def sort(self, column, order):
-        key_func = None
-        if column == 0:
-            def key_func(value):
-                return value.text
-        elif column == 1:
-            def key_func(value):
-                return value.elevation
-
-        if key_func:
+    def sort(self, column_index, order):
+        column = self.COLUMNS[column_index]
+        if column.sortKey is not None:
             self.layoutAboutToBeChanged.emit()
-            self.values.sort(key=key_func, reverse = (order == Qt.DescendingOrder))
+            self.values.sort(key=column.sortKey, reverse = (order == Qt.DescendingOrder))
             self.layoutChanged.emit()