UDC is an analytico-synthetic classification. This means that individual UDC classmarks can be used to build more complex expressions similar to the way we use words to create complex sentences. Special symbols that are used to connect, start or end simple UDC numbers enable the parsing and understanding of complex expressions. This type of notational system is called syntactically-expressive notation. The synthesis of UDC numbers follow fixed syntactic rules that are valid and can be applied to the entire UDC system. Because of the syntactic rules and strict application of notational symbols, UDC complex expressions can be deconstructed accurately into simple UDC numbers