[_Io]

Hola.

Muchas gracias ChatGpt.

Me ha quedado muy claro. Buscando más información he visto que se utiliza bastante en las clase "TRemotable "

Un Fuerte abrazo.

Yes, it is necessary. With this information, for exemple IS_OPTN, the class from TRemotable knows that when property is Optional
to build XML, so if is optional, the node is added only if the value is stored. On your case:

property User: string Index (IS_OPTN) read GetUser write SetUser stored User_Specified

The element User will be added on XML if User_Specified true. The User_Specified turns automatically true when you set value to User, because the setter SetUser do it.

So, when the component SOAP por example, will build the XML, the element will be added only if is stored because it is Optional (IS_OPTN).