diff --git a/src/main/java/net/kemitix/gitdb/Author.java b/src/main/java/net/kemitix/gitdb/Author.java
new file mode 100644
index 0000000..48c8211
--- /dev/null
+++ b/src/main/java/net/kemitix/gitdb/Author.java
@@ -0,0 +1,13 @@
+package net.kemitix.gitdb;
+
+import net.kemitix.mon.TypeAlias;
+
+public class Author extends TypeAlias<String> {
+    protected Author(String value) {
+        super(value);
+    }
+
+    public static Author name(final String name) {
+        return new Author(name);
+    }
+}
diff --git a/src/main/java/net/kemitix/gitdb/Branch.java b/src/main/java/net/kemitix/gitdb/Branch.java
new file mode 100644
index 0000000..094ef6a
--- /dev/null
+++ b/src/main/java/net/kemitix/gitdb/Branch.java
@@ -0,0 +1,13 @@
+package net.kemitix.gitdb;
+
+import net.kemitix.mon.TypeAlias;
+
+public class Branch extends TypeAlias<String> {
+    protected Branch(final String value) {
+        super(value);
+    }
+
+    static Branch name(final String name) {
+        return new Branch(name);
+    }
+}
diff --git a/src/main/java/net/kemitix/gitdb/Document.java b/src/main/java/net/kemitix/gitdb/Document.java
new file mode 100644
index 0000000..348a66a
--- /dev/null
+++ b/src/main/java/net/kemitix/gitdb/Document.java
@@ -0,0 +1,18 @@
+package net.kemitix.gitdb;
+
+import lombok.Getter;
+import lombok.RequiredArgsConstructor;
+
+@RequiredArgsConstructor
+public class Document<T>  {
+
+    public static <T> Document<T> create(Key key, T value) {
+        return new Document<>(key, value);
+    }
+
+    @Getter
+    private final Key key;
+
+    @Getter
+    private final T value;
+}
diff --git a/src/main/java/net/kemitix/gitdb/GitDB.java b/src/main/java/net/kemitix/gitdb/GitDB.java
index 6f9b4cd..5164856 100644
--- a/src/main/java/net/kemitix/gitdb/GitDB.java
+++ b/src/main/java/net/kemitix/gitdb/GitDB.java
@@ -4,6 +4,7 @@ import org.eclipse.jgit.api.errors.GitAPIException;
 import org.eclipse.jgit.lib.Repository;
 
 import java.nio.file.Path;
+import java.util.stream.Stream;
 
 public interface GitDB {
 
@@ -16,4 +17,24 @@ public interface GitDB {
     Repository getRepository();
 
     Path getGitDir();
+
+    String get(Branch branch, Key key);
+
+    <T> T get(Branch branch, Key key, Class<T> type);
+
+    Stream<String> getFiles(Branch branch, Key key);
+
+    <T> Stream<T> getFiles(Branch branch, Key key, Class<T> type);
+
+    <T> T save(Branch branch, Message message, Document<T> document, Author author);
+
+    String delete(Branch branch, Key key, Message message, Author author);
+
+    void tag(Reference reference);
+
+    void createBranch(Reference reference);
+
+    Stream<String> getAllBranches();
+
+    Transaction createTransaction(Branch branch);
 }
diff --git a/src/main/java/net/kemitix/gitdb/GitDBLocal.java b/src/main/java/net/kemitix/gitdb/GitDBLocal.java
index da2593e..5f6954c 100644
--- a/src/main/java/net/kemitix/gitdb/GitDBLocal.java
+++ b/src/main/java/net/kemitix/gitdb/GitDBLocal.java
@@ -6,6 +6,7 @@ import org.eclipse.jgit.api.errors.GitAPIException;
 import org.eclipse.jgit.lib.Repository;
 
 import java.nio.file.Path;
+import java.util.stream.Stream;
 
 class GitDBLocal implements GitDB {
 
@@ -29,4 +30,55 @@ class GitDBLocal implements GitDB {
     public void close() {
         repository.close();
     }
+
+    @Override
+    public String get(Branch branch, Key key) {
+        return null;
+    }
+
+    @Override
+    public <T> T get(Branch branch, Key key, Class<T> type) {
+        return null;
+    }
+
+    @Override
+    public Stream<String> getFiles(Branch branch, Key key) {
+        return null;
+    }
+
+    @Override
+    public <T> Stream<T> getFiles(Branch branch, Key key, Class<T> type) {
+        return null;
+    }
+
+    @Override
+    public <T> T save(Branch branch, Message message, Document<T> document, Author author) {
+        return null;
+    }
+
+    @Override
+    public String delete(Branch branch, Key key, Message message, Author author) {
+        return null;
+    }
+
+    @Override
+    public void tag(Reference reference) {
+
+    }
+
+    @Override
+    public void createBranch(Reference reference) {
+
+    }
+
+    @Override
+    public Stream<String> getAllBranches() {
+        return null;
+    }
+
+    @Override
+    public Transaction createTransaction(Branch branch) {
+        return null;
+    }
+
 }
diff --git a/src/main/java/net/kemitix/gitdb/Key.java b/src/main/java/net/kemitix/gitdb/Key.java
new file mode 100644
index 0000000..2aca0f5
--- /dev/null
+++ b/src/main/java/net/kemitix/gitdb/Key.java
@@ -0,0 +1,13 @@
+package net.kemitix.gitdb;
+
+import net.kemitix.mon.TypeAlias;
+
+public class Key extends TypeAlias<String> {
+    protected Key(final String value) {
+        super(value);
+    }
+
+    public static Key name(final String name) {
+        return new Key(name);
+    }
+}
diff --git a/src/main/java/net/kemitix/gitdb/Message.java b/src/main/java/net/kemitix/gitdb/Message.java
new file mode 100644
index 0000000..22902da
--- /dev/null
+++ b/src/main/java/net/kemitix/gitdb/Message.java
@@ -0,0 +1,12 @@
+package net.kemitix.gitdb;
+
+import net.kemitix.mon.TypeAlias;
+
+public class Message extends TypeAlias<String> {
+    protected Message(final String value) {
+        super(value);
+    }
+    public static Message message(final String message) {
+        return new Message(message);
+    }
+}
diff --git a/src/main/java/net/kemitix/gitdb/Reference.java b/src/main/java/net/kemitix/gitdb/Reference.java
new file mode 100644
index 0000000..fb84c69
--- /dev/null
+++ b/src/main/java/net/kemitix/gitdb/Reference.java
@@ -0,0 +1,9 @@
+package net.kemitix.gitdb;
+
+import net.kemitix.mon.TypeAlias;
+
+public class Reference extends TypeAlias<String> {
+    protected Reference(String value) {
+        super(value);
+    }
+}
diff --git a/src/main/java/net/kemitix/gitdb/Transaction.java b/src/main/java/net/kemitix/gitdb/Transaction.java
new file mode 100644
index 0000000..c396875
--- /dev/null
+++ b/src/main/java/net/kemitix/gitdb/Transaction.java
@@ -0,0 +1,9 @@
+package net.kemitix.gitdb;
+
+import net.kemitix.mon.TypeAlias;
+
+public class Transaction extends TypeAlias<String> {
+    protected Transaction(String value) {
+        super(value);
+    }
+}