diff --git a/src/main/python/ddadevops/__init__.py b/src/main/python/ddadevops/__init__.py
index 8f5924d..3df0197 100644
--- a/src/main/python/ddadevops/__init__.py
+++ b/src/main/python/ddadevops/__init__.py
@@ -19,4 +19,7 @@ from .devops_terraform_build import DevopsTerraformBuild, create_devops_terrafor
 from .devops_build import DevopsBuild, create_devops_build_config, get_devops_build, get_tag_from_latest_commit
 from .credential import gopass_password_from_path, gopass_field_from_path
 
+from .domain import Validateable, Build
+from .application import BuildService
+
 __version__ = "${version}"
diff --git a/src/main/python/ddadevops/application.py b/src/main/python/ddadevops/application.py
new file mode 100644
index 0000000..014f871
--- /dev/null
+++ b/src/main/python/ddadevops/application.py
@@ -0,0 +1,8 @@
+from .domain import Build
+from .python_util import execute
+
+
+class BuildService():
+    def initialize_build_dir(self, build: Build):
+        execute('rm -rf ' + build.build_path(), shell=True)
+        execute('mkdir -p ' + build.build_path(), shell=True)
diff --git a/src/main/python/ddadevops/devops_build.py b/src/main/python/ddadevops/devops_build.py
index 4c6f403..d48999b 100644
--- a/src/main/python/ddadevops/devops_build.py
+++ b/src/main/python/ddadevops/devops_build.py
@@ -1,5 +1,5 @@
-from subprocess import run, CalledProcessError
-from .python_util import filter_none
+from .domain import Build
+from .application import BuildService
 
 def create_devops_build_config(stage, project_root_path, module,
                                build_dir_name='target'):
@@ -11,48 +11,26 @@ def create_devops_build_config(stage, project_root_path, module,
 def get_devops_build(project):
     return project.get_property('devops_build')
 
-def get_tag_from_latest_commit():
-    try:
-        value = run('git describe --abbrev=0 --tags --exact-match', shell=True,
-            capture_output=True, check=True)
-        return value.stdout.decode('UTF-8').rstrip()
-    except CalledProcessError:
-        return None
+# def get_tag_from_latest_commit():
+#     try:
+#         value = run('git describe --abbrev=0 --tags --exact-match', shell=True,
+#             capture_output=True, check=True)
+#         return value.stdout.decode('UTF-8').rstrip()
+#     except CalledProcessError:
+#         return None
 
 class DevopsBuild:
 
     def __init__(self, project, config):
-        #deprecate stage
-        self.stage = config['stage']
-        self.project_root_path = config['project_root_path']
-        self.module = config['module']
-        self.build_dir_name = config['build_dir_name']
-        self.stack = {}
-        self.project = project
+        self.build = Build(project, config)
+        self.build_service = BuildService()
         project.set_property('devops_build', self)
 
     def name(self):
-        return self.project.name
+        return self.build.name()
 
     def build_path(self):
-        mylist = [self.project_root_path,
-                  self.build_dir_name,
-                  self.name(),
-                  self.module]
-        return '/'.join(filter_none(mylist))
+        return self.build.build_path()
 
     def initialize_build_dir(self):
-        run('rm -rf ' + self.build_path(), shell=True, check=True)
-        run('mkdir -p ' + self.build_path(), shell=True, check=True)
-
-    def put(self, key, value):
-        self.stack[key] = value
-
-    def get(self, key):
-        return self.stack[key]
-
-    def get_keys(self, keys):
-        result = {}
-        for key in keys:
-            result[key] = self.get(key)
-        return result
+        self.build_service.initialize_build_dir(self.build)
diff --git a/src/main/python/ddadevops/domain.py b/src/main/python/ddadevops/domain.py
new file mode 100644
index 0000000..5c6c1b7
--- /dev/null
+++ b/src/main/python/ddadevops/domain.py
@@ -0,0 +1,50 @@
+from typing import List
+from .python_util import filter_none
+
+
+class Validateable():
+    def validate(self) -> List[str]:
+        return []
+
+    def is_valid(self) -> bool:
+        return len(self.validate()) < 1
+
+    def validate_is_not_empty(self, field_name: str) -> List[str]:
+        value = self.__dict__[field_name]
+        if value is None or value == '':
+            return [f"Field '{field_name}' may not be empty."]
+        else:
+            return []
+
+class Build(Validateable):
+
+    def __init__(self, project, config):
+        # deprecate stage
+        self.stage = config['stage']
+        self.project_root_path = config['project_root_path']
+        self.module = config['module']
+        self.build_dir_name = config['build_dir_name']
+        self.stack = {}
+        self.project = project
+
+    def name(self):
+        return self.project.name
+
+    def build_path(self):
+        path = [self.project_root_path,
+                self.build_dir_name,
+                self.name(),
+                self.module]
+        return '/'.join(filter_none(path))
+
+    def put(self, key, value):
+        self.stack[key] = value
+
+    def get(self, key):
+        return self.stack[key]
+
+    def get_keys(self, keys):
+        result = {}
+        for key in keys:
+            result[key] = self.get(key)
+        return result
diff --git a/src/test/test_domain.py b/src/test/test_domain.py
new file mode 100644
index 0000000..861f850
--- /dev/null
+++ b/src/test/test_domain.py
@@ -0,0 +1,41 @@
+from src.main.python.ddadevops.domain import Validateable
+
+
+class TestValidateable(Validateable):
+    def __init__(self, value):
+        self.field = value
+
+    def validate(self):
+        return self.validate_is_not_empty('field')
+
+
+def test_should_validate_non_empty_strings():
+
+    sut = TestValidateable("content")
+    assert sut.is_valid()
+
+    sut = TestValidateable(None)
+    assert not sut.is_valid()
+
+    sut = TestValidateable('')
+    assert not sut.is_valid()
+
+
+def test_should_validate_non_empty_others():
+
+    sut = TestValidateable(1)
+    assert sut.is_valid()
+
+    sut = TestValidateable(1.0)
+    assert sut.is_valid()
+
+    sut = TestValidateable(True)
+    assert sut.is_valid()
+
+    sut = TestValidateable(None)
+    assert not sut.is_valid()
+
+def test_validate_with_reason():
+
+    sut = TestValidateable(None)
+    assert sut.validate()[0] == "Field 'field' may not be empty."