diff --git a/README.md b/README.md
index 2edb129..d306e7a 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,5 @@
 # Todo 
 ## Next steps
-- onvalidate function, check illegal chars in names, name collitions
 - use builders for entities/fields/keys
 - make work for mariadb/mysql
   - add database object to context with
diff --git a/src/main/java/jef/model/DbContext.java b/src/main/java/jef/model/DbContext.java
index 582a26f..fa31dc6 100644
--- a/src/main/java/jef/model/DbContext.java
+++ b/src/main/java/jef/model/DbContext.java
@@ -1,6 +1,82 @@
 package jef.model;
 
+import jef.model.constraints.ForeignKeyConstraint;
+import jef.serializable.SerializableObject;
+
+import java.lang.reflect.Field;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Optional;
+import java.util.stream.Collectors;
+
 public abstract class DbContext {
+    private static final String ILLEGAL_CHARACTERS = "\"'`,.";//TODO also validate this in modelbuilder/dbentity/dbfield
+
     public void onModelCreate(ModelBuilder mb) {
     }
+
+    public void onModelValidate(ModelBuilder mb) {
+        var errors = new ArrayList<String>();
+
+        //check for illegal characters
+        for (var entity : mb.getEntities()) {
+            if (entity.getName().matches("[" + ILLEGAL_CHARACTERS + "]")) {
+                errors.add("DbEntity " + entity.getTypeName() + " has illegal characters in its name: " + entity.getName());
+            }
+            for (var field : entity.getFields()) {
+                if (field.getName().matches("[" + ILLEGAL_CHARACTERS + "]")) {
+                    var fieldname = Optional.ofNullable(field.getField()).map(Field::getName).orElse(field.getName());
+                    errors.add("DbField " + entity.getTypeName() + "::" + fieldname + " has illegal characters in its name: " + entity.getName());
+                }
+            }
+        }
+
+        //check for duplicate entity names
+        var entityNameMap = new HashMap<String, DbEntity<?>>();
+        for (DbEntity<? extends SerializableObject> entity : mb.getEntities()) {
+            var name = entity.getName().toLowerCase();
+            if (entityNameMap.containsKey(name)) {
+                errors.add("Duplicate DbEntity with name " + entity.getName() + ": " + entity.getTypeName() + " and " + entityNameMap.get(name).getTypeName());
+            } else {
+                entityNameMap.put(name, entity);
+            }
+        }
+
+        //check for duplicate field names
+        for (DbEntity<? extends SerializableObject> entity : mb.getEntities()) {
+            var fieldNameMap = new HashMap<String, DbEntity<?>>();
+            for (DbField<?> field : entity.getFields()) {
+                var name = field.getName().toLowerCase();
+                if (fieldNameMap.containsKey(name)) {
+                    errors.add("Duplicate DbField in entity " + entity.getTypeName() + " with name " + field.getName() + ": " + field.getName() + " and " + fieldNameMap.get(name).getName());
+                } else {
+                    fieldNameMap.put(name, entity);
+                }
+            }
+        }
+
+        //check foreign keys for existing primary keys
+        for (DbEntity<? extends SerializableObject> entity : mb.getEntities()) {
+            for (ForeignKeyConstraint foreignKey : entity.getForeignKeys()) {
+                //verify primary key exists
+                if (foreignKey.getReferencedEntity().getPrimaryKey() == null) {
+                    errors.add("DbEntity " + entity.getTypeName() + " has a foreign key constraint to " + foreignKey.getReferencedEntity().getTypeName()
+                               + " which does not have primary key");
+                }
+                //verify field count, names, types, and order
+                else if (!foreignKey.getReferencedEntity().getPrimaryKey().getFields().equals(foreignKey.getReferencedFields())) {
+                    errors.add("DbEntity " + entity.getTypeName() + " has a foreign key constraint to " + foreignKey.getReferencedEntity().getTypeName()
+                               + " where the specified fields do not match: referring fields ["
+                               + foreignKey.getReferencedFields().stream().map(DbField::getName).collect(Collectors.joining(", "))
+                               + "] but found referenced fields ["
+                               + foreignKey.getReferencedEntity().getPrimaryKey().getFields().stream().map(DbField::getName).collect(Collectors.joining(", "))
+                               + "]");
+                }
+            }
+        }
+
+        if (!errors.isEmpty()) {
+            throw new ModelException(String.join("\n", errors));
+        }
+    }
 }
diff --git a/src/main/java/jef/model/DbEntity.java b/src/main/java/jef/model/DbEntity.java
index 3976f10..187d9ff 100644
--- a/src/main/java/jef/model/DbEntity.java
+++ b/src/main/java/jef/model/DbEntity.java
@@ -179,17 +179,12 @@ public class DbEntity<T extends SerializableObject> {
         return this.indexes.remove(index);
     }
 
-    private <R> String extractFieldName(SerializableFunction<T, R> getter) {
-        try {
-            var expr = new AsmParser(getter).parse();
-            if (expr.getType() != Expression.Type.INTERMEDIATE_FIELD) {
-                throw new RuntimeException(expr.getClass().getSimpleName() + " is not a field expression");
-            }
-            var name = ((IntermediateFieldExpression) expr).getName();
-            return name;
-        } catch (AsmParseException e) {
-            throw new RuntimeException("Invalid expression", e);
-        }
+    /**
+     * Does not validate foreign key integrity
+     * @param primaryKey
+     */
+    public void setPrimaryKey(PrimaryKeyConstraint primaryKey) {
+        this.primaryKey = primaryKey;
     }
 
     public void addForeignKey(ForeignKeyConstraint foreignKey) {
@@ -216,6 +211,19 @@ public class DbEntity<T extends SerializableObject> {
         }
     }
 
+    private <R> String extractFieldName(SerializableFunction<T, R> getter) {
+        try {
+            var expr = new AsmParser(getter).parse();
+            if (expr.getType() != Expression.Type.INTERMEDIATE_FIELD) {
+                throw new RuntimeException(expr.getClass().getSimpleName() + " is not a field expression");
+            }
+            var name = ((IntermediateFieldExpression) expr).getName();
+            return name;
+        } catch (AsmParseException e) {
+            throw new RuntimeException("Invalid expression", e);
+        }
+    }
+
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;
diff --git a/src/main/java/jef/model/ModelBuilder.java b/src/main/java/jef/model/ModelBuilder.java
index a35d711..1aec282 100644
--- a/src/main/java/jef/model/ModelBuilder.java
+++ b/src/main/java/jef/model/ModelBuilder.java
@@ -56,6 +56,7 @@ public class ModelBuilder {
 
         var instance = context.getDeclaredConstructor().newInstance();//TODO find constructor, //TODO optionally with config
         instance.onModelCreate(mb);
+        instance.onModelValidate(mb);
 
         return mb;
     }
diff --git a/src/main/java/jef/model/migration/creator/MigrationCreator.java b/src/main/java/jef/model/migration/creator/MigrationCreator.java
index 48c1058..74a1a24 100644
--- a/src/main/java/jef/model/migration/creator/MigrationCreator.java
+++ b/src/main/java/jef/model/migration/creator/MigrationCreator.java
@@ -33,7 +33,7 @@ import java.util.List;
 import java.util.stream.Collectors;
 
 public class MigrationCreator {
-    private static final String ILLEGAL_CHARACTERS = "\"'`,.";//TODO also validate this in modelbuilder/dbentity/dbfield
+
 
     public Result createMigration(ModelBuilder from, ModelBuilder to, String name, String packageName, String currentSnapshotJava) {
         var result = new Result();
@@ -70,18 +70,6 @@ public class MigrationCreator {
     }
 
     private Result generateMigration(ModelBuilder from, ModelBuilder to, String name, String packageName, Result result) {
-        //check for illegal characters
-        for (var entity : to.getEntities()) {
-            if (entity.getName().matches("[" + ILLEGAL_CHARACTERS + "]")) {
-                throw new ModelException("Entity " + entity.getType().getSimpleName() + " has illegal characters in its name: " + entity.getName());
-            }
-            for (var field : entity.getFields()) {
-                if (field.getName().matches("[" + ILLEGAL_CHARACTERS + "]")) {
-                    throw new ModelException("Field " + entity.getType().getSimpleName() + "::" + field.getField().getName() + " has illegal characters in its name: " + entity.getName());
-                }
-            }
-        }
-
         //reduce model builders to changes
         var mcd = new ModelChangeDetector(from, to).detect();
         var fromReduced = mcd.getFrom();