diff --git a/soup.py b/soup.py
new file mode 100644
index 0000000..72af680
--- /dev/null
+++ b/soup.py
@@ -0,0 +1,75 @@
+from xml.dom import Node as NodeType
+
+from bs4 import BeautifulSoup
+from bs4.element import Doctype
+
+
+EXAMPLE_HTML = """\
+<!DOCTYPE html>
+<html>
+<head>
+<title>Page Title</title>
+</head>
+<body>
+
+<h1>This is a Heading</h1>
+<p>This is a paragraph.</p>
+
+</body>
+</html>
+"""
+
+class Node:
+    def __init__(self, parent_id, name=None):
+        self.parent_id = parent_id
+        self.name = name
+
+    def __str__(self):
+        return f"Node(parent={self.parent_id}, name={self.name}"
+
+
+class DocumentNode(Node):
+    BS4_TYPE = BeautifulSoup
+
+    def __init__(self, src, parent_id):
+        super().__init__(parent_id)
+        assert self.parent_id == -1
+
+
+class DocumentTypeNode(Node):
+    BS4_TYPE = Doctype
+
+    def __init__(self, src, parent_id):
+        super().__init__(parent_id, name=str(src))
+
+
+class TreeBuilder:
+    NODE_CLASSES = (
+        DocumentNode,
+        DocumentTypeNode,
+    )
+
+    def __init__(self):
+        self.nodes = []
+
+    def visit(self, node, parent_id=-1):
+        for node_class in self.NODE_CLASSES:
+            if isinstance(node, node_class.BS4_TYPE):
+                break
+        else:
+            raise NotImplementedError(type(node))
+
+        node_id = len(self.nodes)
+        self.nodes.append(node_class(node, parent_id))
+        print(self.nodes[-1])
+        for child in getattr(node, "children", ()):
+            self.visit(child, node_id)
+
+
+def main(html=EXAMPLE_HTML):
+    tree = TreeBuilder()
+    tree.visit(BeautifulSoup(html, "html.parser"))
+
+
+if __name__ == "__main__":
+    main()
