Load default settings if the user does not specify a path.

cml/controller/api.py

 """Entry point.
 
 """
-from cml.usecases.query import PreprocessUsecase
+from os.path import join, expanduser
+
+from cml.usecases.query import PreprocessUsecase, KnowledgeSearchUsecase
 from cml.ports.source_adapters import PandasAdapter
 from cml.shared.settings import Settings
 from cml.shared.settings import specific_settings_factory, read_settings
@@ -22,6 +24,20 @@ __all__ = (
 )
 
 
+def default_path(func):
+    def wrapper(path: str = None):
+        if not path:
+            path = join(expanduser("~"), ".cml", "settings.ini")
+
+        try:
+            func(path)
+        except FileNotFoundError as e:
+            # TODO (dmt):Provide proper exception handling!
+            pass
+    return wrapper
+
+
+@default_path
 def load_settings(path: str):
     read_settings(path)