Elements get validated in that:

• What attributes have occurred is checked against those allowed and those required.

• Attributes are validated.

• If the content is simple typed, the character children is checked against this type.

• The order of the element children is checked against the type of the element.

• Element children are validated against their declarations.

Attributes get validated against their type and "use" (defaults, optional vs. required, etc.).

Assessment starts by finding an element declaration and a processing mode of 'lax' or 'strict'.