The ContentFilter structure defines a collection of elements that define filtering criteria. Each element in the collection describes an operator and an array of operands to be used by the operator. The operators that can be used in a ContentFilter are described in Table 122. The filter is evaluated by evaluating the first entry in the element array starting with the first operand in the operand array. The operands of an element may contain References to sub-elements resulting in the evaluation continuing to the referenced elements in the element array. The evaluation shall not introduce loops. For example evaluation starting from element “A” shall never be able to return to element “A”. However there may be more than one path leading to another element “B”. If an element cannot be traced back to the starting element it is ignored. Extra operands for any operator shall result in an error. Annex B provides examples using the ContentFilter structure.

Table 118 defines the ContentFilter structure.

Table 118 – ContentFilter structure

Name	Type	Description
ContentFilter	structure
elements []	ContentFilterElement	List of operators and their operands that compose the filter criteria. The filter is evaluated by starting with the first entry in this array. This structure is defined in-line with the following indented items.
filterOperator	Enum FilterOperator	Filter operator to be evaluated. The FilterOperator enumeration is defined in Table 122.
filterOperands []	Extensible Parameter FilterOperand	Operands used by the selected operator. The number and use depend on the operators defined in Table 122. This array needs at least one entry. This extensible parameter type is the FilterOperand parameter type specified in 7.7.4. It specifies the list of valid FilterOperand values.