Standard way to tell XML parsers that child is a singleton as opposed to a list

xml-question.md

Say we have this XML

<bookstore>
  <book>art of war</book>
</bookstore

Most bookstores have many books, so we'd probably be right to assume that books is a list. However, my question is, does XML have a standard way to declare that a child should be a singleton? Something like this:

<bookstore   single="book">  
  <book>art of war</book>
</bookstore

The "single" attribute would tell the parser, that there is only one instance of book. If there is more than one book, it would throw a parsing error.

On the flipside, perhaps there is an XML standard to tell parsers that the child is a list? Something like this:

<bookstore    list="book">
  <book>art of war</book>
  <book>moby dick</book>
</bookstore

Then parsers could safely assume that there will be many books in the bookstore.

There is a standard, it's just in the javascript world everyone seems to forget things called schemas. Proper XML tools in most languages when doing parsing, code gen etc will use and respect a schema.

The schema can tell you if a child is a list via the schema properties, minOccurs, maxOccurs, mustOccurs, e.g. if minOccurs and maxOccurs = 1 then its a single element not a list, if it had minOccurs=0 and no maxOccurs then it would be optional list