Some helpers to build a new object.

1. The order of coming elements is:
   • all elements for the 1-st boundary
   • 2-st boundary
   • the rules between them
   • 3-st boundary (if exists)
   • its rules
   • etc
2. All boundaries should have the same structure (the same types, order of elements)
3. Their types should correlate with their purpose
4. These methods can throw exceptions if element mismatch their purpose
5. The class of an element changes according to the purpose