XML hierarchy

After the Input or Output Message Format panel is opened, XML message formats display as a hierarchical tree, similar to the other message formats. XML does not employ rigid message definitions.

XML messages have the potential to be infinitely deep in hierarchy. With the XML specification, you can use concepts such as "recursion" and introduces more detail to repeatability. As a consequence, the tree structure that is shown in the dialog box is often more complex than with other message formats.

This shows the representation of the DTD:

<!ELEMENT alpha2 ((gamma,foo)+,(delta,foo)*)+>
<!ATTLIST alpha2
          one CDATA#IMPLIED>
<!ELEMENT beta EMPTY>
<!ELEMENT gtamma (delta,foo)+>
<!ELEMENT delta (#PCDATA|beta|foo)*>
<!ELEMENT foo (#PCDATA)>

The names that are shown on the tree nodes correspond to XML elements or attributes. Tree lines, indentations, and node icons represent the hierarchy of the elements.

Element repeatability is represented by the syntax (#,#). For example, (1,1) is "one and only one" and (1,-1) is "one or more."

Element sequencing is represented by the symbol (_), where "_" can be occupied by one of:

  • Comma (,), which represents the concept of list.
  • Pipe (|), which represents the concept of or.

Attributes are designated with an ampersand (&).