Container
Containers are properties that have no intrinsic data value themselves but instead are for a collection of related properties that convey a concept. Hence, an element classified as Container has no base type. For example ask, volume, etc. are classified as Containers.

Example (“ask” is a “Container”):
<ask>
  <last>102.34</last>
  <open>102.21</open>
</ask>

For each MDDL element defined as a Product, an additional container element is defined postfixed with the designation Group. For example, the entityDomain element has a corresponding entityDomainGroup. The Group is only a child of its respective product.

The Group container is used as a holder of properties that are common to all of its children. A product may contain multiple Groups where each Group defines a different set of common properties to be inherited by all of its descendants. For example, an instrumentDomain product in an instance may contain two instrumentDomainGroup child elements where one defines a currency of Euros and the other defines a currency of Japanese Yen.