在lxml中，可以使用include和fallback指令来实现XML文档的模块化解析。
<!DOCTYPE html [
<!ENTITY myInclude SYSTEM "included.xml">
]>
<html>
&myInclude;
</html>
<!DOCTYPE html [
<!ENTITY myInclude SYSTEM "included.xml" NDATA fallback>
]>
<html>
&myInclude;
</html>
通过使用include和fallback指令，可以更好地实现XML文档的模块化解析，提高XML文档的可维护性和可读性。