Answer: How to make type depend on attribute value using Conditional Type Assignment

You can do this using XSD 1.1's Conditional Type Assignment:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:vc="http://www.w3.org/2007/XMLSchema-versioning"
           elementFormDefault="qualified"
           vc:minVersion="1.1"> 
  <xs:element name="listOfA">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="a" maxOccurs="unbounded">
          <xs:alternative test="@type = 1" type="a1Type"/>        
          <xs:alternative test="@type = 2" type="a2Type"/>
        </xs:element>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
  <xs:complexType name="a1Type">
    <xs:sequence>
      <xs:element name="name"/>
      <xs:element name="surname"/>
    </xs:sequence>
  </xs:complexType>
  <xs:complexType