Content model is a term used to describe the set of elements and attributes contained inside another XML element. Although the XML Schema specification is explicit about how schemas should be presented in XML, there is no commonly agreed-upon format for symbols representing information in schema diagrams. Schema editors and viewers have different approaches to diagramming. The diagrams in MCS documentation use the following conventions.
Content model is a term used to describe the set of elements and attributes contained inside another XML element. Although the XML Schema specification is explicit about how schemas should be presented in XML, there is no commonly agreed-upon format for symbols representing information in schema diagrams. Schema editors and viewers have different approaches to diagramming. The diagrams in MCS documentation use the following conventions.
The diagrams show the structure and cardinality of the elements used in these structures. Attributes are not shown.
xs:sequence
In the first figure, the symbol in the center, with the horizontal dotted line, indicates a sequence. This diagram says the select element consists of the sequence of when and otherwise elements. The boxes with a plus (+) indicates that there is hidden content not shown in the diagram. An arrow on an element indicates that it refers to a declaration elsewhere in the schema. The dotted line around the elements indicates they are optional.
xs:choice or xs:all
The switchlike symbol in the next figure indicates a choice; in this case, a choice between one or more td or th elements. The solid line around the elements shows that one or other is required.
Another way of providing a choice is to use the following structure. The symbol is for the xs:all element that allows the contained elements to occur in any order, either once only or not at all.
Cardinality
Cardinality expresses constraints about the minimum and maximum occurrences of elements. The number of times it may appear is given by the text with it. In the final figure 1..∞ means the minOccurs attribute has a value of 1 and maxOccurs is unbounded (infinity). If there is no such text, the diagram is showing that it can occur only once.
The diagram shows some additional information. The row of bars on the td and th elements indicates that only text content is allowed.
