XML Inclusion and Parsing

How to include one xml in another xml

I have like this for example

xml 1:

 <Appointment>
<b1>Example1</b1>
<b2>Example2</b2>
</Appointment>

xml2:

<Calendar>
<time>24</time>
<day>may05</day>
<Calendar>

The schema is defined in a way
<xs:Element name="Appointment" type="AppointmentType">

<xs:complexType name="AppointmentType">
<xs:sequence>
<xs:element name="Entity" type="b1" minOccurs="1" maxOccurs="unbounded" />
<xs:element name="Entity" type="b2" minOccurs="1" maxOccurs="unbounded" />
<xs:element name="Entity" type="Calendar" minOccurs="1" maxOccurs="unbounded" />
</xs:sequence>
</xs:complexType>

How can I do this and also how to parse this without an errors? Appreciate your answers