I'm looking at the documentation, and it doesn't actually say that indicators (sequence, all, choice) are required. But if I remove the indicators from an xsd that contains them, it does not validate. I wish to create a schema that allows the elements to appear in any order, some of the elements can appear multiple times, and some of the elements are optional. So, this means that, "all" is not suitable, because some of the elements may appear more than once. I do not wish to use the "choice" indicator, because it would add undue complexity to what we are doing. I do not wish to use the "sequence" indicator, because I have been told that the elements may appear in any order. But if I do not use any of these three, the .xsd is considered invalid according to the online validator. Any thoughts?