diff --git a/the_works/models.py b/the_works/models.py
index 59cd9a6..1ce5b17 100644
--- a/the_works/models.py
+++ b/the_works/models.py
@@ -1,9 +1,7 @@
-# code is built upon output from sqlacodegen
-
 import sys
 from typing import List, Optional
 from sqlalchemy import ForeignKey, types
-from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column, relationship
+from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column, relationship, validates
 from sqlalchemy.ext.associationproxy import AssociationProxy, association_proxy
 from flask import url_for
 
@@ -22,7 +20,12 @@ class Base(DeclarativeBase):
     return d
 
   def __repr__(self) -> str:
-    return f"{type(self).__name__}({str(self.asdict())})"    
+    return f"{type(self).__name__}({str(self.asdict())})"
+
+  def validate_not_empty(self, value):
+    if not value:
+      raise ValueError("value can't be empty")
+    return value
 
 
 class Genre(Base):
@@ -34,6 +37,9 @@ class Genre(Base):
   texte: Mapped[List['Text_Genre']] = relationship(back_populates='genre')
   werke: Mapped[List['Werk_Genre']] = relationship(back_populates='genre')
 
+  @validates("Genre")
+  def validate_genre(self, key, value):
+    return self.validate_not_empty(value)
 
 class Herausgeber(Base):
   __tablename__ = 'Herausgeber'
@@ -43,6 +49,10 @@ class Herausgeber(Base):
 
   werke: Mapped[List['Werk_Herausgeber']] = relationship(back_populates='herausgeber')
 
+  @validates("Herausgeber")
+  def validate_herausgeber(self, key, value):
+    return self.validate_not_empty(value)
+
 
 class Pseudonym(Base):
   __tablename__ = 'Pseudonym'
@@ -52,6 +62,10 @@ class Pseudonym(Base):
 
   veroeffentlichung: Mapped[List['Veroeffentlichung']] = relationship(back_populates='pseudonym')
 
+  @validates("Pseudonym")
+  def validate_pseudonym(self, key, value):
+    return self.validate_not_empty(value)
+
 
 class Sprache(Base):
   __tablename__ = 'Sprache'
@@ -61,6 +75,10 @@ class Sprache(Base):
 
   text: Mapped[List['Text']] = relationship(back_populates='sprache')
 
+  @validates("Sprache")
+  def validate_sprache(self, key, value):
+    return self.validate_not_empty(value)
+
 
 class Textform(Base):
   __tablename__ = 'Textform'
@@ -70,6 +88,10 @@ class Textform(Base):
 
   text: Mapped[List['Text']] = relationship(back_populates='textform')
 
+  @validates("Textform")
+  def validate_textform(self, key, value):
+    return self.validate_not_empty(value)
+
 
 class Titelbild(Base):
   __tablename__ = 'Titelbild'
@@ -92,6 +114,10 @@ class Titelbild(Base):
     tb["Thumbnail"] = url_for("titelbild.thumbnail", id=self.ID)
     return tb
 
+  @validates("sha256")
+  def validate_titelbild(self, key, value):
+    return self.validate_not_empty(value)
+
 
 class Verlag(Base):
   __tablename__ = 'Verlag'
@@ -102,6 +128,10 @@ class Verlag(Base):
   reihe: Mapped[List['Reihe']] = relationship(back_populates='verlag')
   werk: Mapped[List['Werk']] = relationship(back_populates='verlag')
 
+  @validates("Verlag")
+  def validate_verlag(self, key, value):
+    return self.validate_not_empty(value)
+
 
 class Werksform(Base):
   __tablename__ = 'Werksform'
@@ -111,6 +141,10 @@ class Werksform(Base):
 
   werk: Mapped[List['Werk']] = relationship(back_populates='werksform')
 
+  @validates("Werksform")
+  def validate_werksform(self, key, value):
+    return self.validate_not_empty(value)
+
 
 class Reihe(Base):
   __tablename__ = 'Reihe'
@@ -124,6 +158,10 @@ class Reihe(Base):
   text: Mapped[List['Text']] = relationship(back_populates='reihe')
   werk: Mapped[List['Werk']] = relationship(back_populates='reihe')
 
+  @validates("Titel")
+  def validate_titel(self, key, value):
+    return self.validate_not_empty(value)
+
 
 class Text(Base):
   __tablename__ = 'Text'
@@ -148,6 +186,10 @@ class Text(Base):
   genres: Mapped[List['Text_Genre']] = relationship(back_populates='text', cascade="all, delete-orphan")
   genre_ids: AssociationProxy[List["Genre"]] = association_proxy("genres", "Genre", creator=lambda genre_id: Text_Genre(Genre=genre_id))
 
+  @validates("Titel")
+  def validate_titel(self, key, value):
+    return self.validate_not_empty(value)
+
 
 class Werk(Base):
   __tablename__ = 'Werk'
@@ -184,6 +226,10 @@ class Werk(Base):
   herausgeber: Mapped[List['Werk_Herausgeber']] = relationship(back_populates='werk', cascade="all, delete-orphan")
   herausgeber_ids: AssociationProxy[List['Herausgeber']] = association_proxy("herausgeber", "Herausgeber", creator=lambda hrsg_id: Werk_Herausgeber(Herausgeber=hrsg_id))
 
+  @validates("Titel")
+  def validate_titel(self, key, value):
+    return self.validate_not_empty(value)
+
 
 class Veroeffentlichung(Base):
   __tablename__ = 'Veroeffentlichung'