data inheritance

Author: oscarotero

docs/4.syntax/12.data-inheritance.md

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+# Data inheritance
+
+Vento has a parent to child data inheritance system:
+
+## Child templates have access to the parent's data
+
+When a template includes another template (using [include](./6.include.md) or [layout](./7.layout.md)), the children template can access to the parent data. For example:
+
+```vto
+{{ set value = "Hello world" }}
+
+{{ include "child.vto" }}
+```
+
+The child template can access to the parent variable:
+
+```vto
+{{ value }}
+```
+
+This doesn't happen in reverse order. A variable declared in a child component cannot be accessed by the parent template.
+
+## Parent templates can edit children variables
+
+Parent templates can create or modify existing variables before rendering nested templates. For example:
+
+```vto
+{{ set value = "Hello world" }}
+
+{{ include "child.vto" { value: "Other value", foo: "bar" } }}
+```
+
+In this example, the parent variable modifies the `value` variable and creates the `foo` variable. These changes are only available in the context of the child template (and successive nested templates).