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DOCUMENTATION.md

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+# Documentation
+
+```mermaid
+
+erDiagram
+    NodeType ||--o{ NodeInput : has
+    NodeType ||--o{ NodeOutput : has
+    NodeType ||--o{ NodeTheme : has
+    NodeInput ||--|| ValueType : uses
+    NodeOutput ||--|| ValueType : uses
+    ValueType ||..|| InputType : uses
+    NodeInput{
+        string name
+        string id
+        ValueType valueType
+        boolean isArray
+        boolean isConstant
+        any defaultValue
+        string inputGroup
+    }
+    NodeOutput{
+        string name
+        string id
+        ValueType valueType
+        boolean isArray
+    }
+    NodeTheme{
+        string name
+        string color
+    }
+    NodeType{
+        string name
+        string id
+        string description
+        NodeInput[] inputs
+        NodeOutput[] outputs
+        NodeTheme theme
+    }
+    ValueType{
+        string name
+        string color
+        string inputType
+        any defaultValue
+    }
+```
+
+## NodeType
+
+A node type describes a kind of node that can put in a graph. It has a name and a list of inputs and outputs that have handles to connect to other nodes via edges.
+
+## NodeInput
+
+A node input is a handle that can be connected to a node output via an edge. 
+