Model Group Properties in XML Schemas

l all specifies that each element must appear exactly zero or one time. The elements can appear in any order. In an instance document, the children of the group or complexType can include 0 or 1 instance of each element.

l choice specifies that exactly one element can be present, and there must be only one instance of that element. In an instance document, exactly one element can be a child of the group or complexType.

l sequence specifies that the elements must appear in the order in which they are specified in the schema. For each element, you can specify whether it is optional and whether it can appear more than once. The default is that exactly one must be present in an instance document. In an instance document, each element that appears must be in the same order as in the schema.

Another value you can specify is any. When you specify any, you do not add any element definitions or references to elements. As the name implies, any element can appear any number of times.