6.2.1 Record type and values

ElementId shall resolve to the name of a field in the structured type

Elements of a record shall be referenced by the dot notation TypeIdOrExpression.ElementId, where TypeIdOrExpression resolves to the name of a structured type or an expression of a structured type such as variable, formal parameter, module parameter, constant, template, or function invocation

Fields of record type definitions shall not reference themselves.

If a field in a record type or a subtype of a record type is referenced by the dot notation, the resulting type is the set of values allowed for that field imposed by the constraints of the field declaration itself (i.e. any constraints applied to the record type itself are ignored).

Optional elements in a record shall be specified using the optional keyword.

Optional fields shall be omitted using the omit symbol.

TTCN3 supports the definition of types for record fields nested within the record definition. Both the definition of new structured types (record, set, enumerated, set of, record of, and union) and the specification of subtype constraints are possible.

optional fields, not directly referred to in the notation, shall implicitly be set to omit

while mandatory fields shall remain unchanged (see also clause 27.7).

In this way, a value with initialized fields or elements can be made empty by using an empty pair of curly brackets ("{}").

already initialized fields or elements left without an associated component in a value list notation (i.e. at the end of a value ) are becoming uninitialized

Fields or elements to be left unchanged shall be explicitly skipped in the list by using the not-used-symbol "-".

No empty assignment is allowed (i.e. two commas, the second immediately following the first or only with white space between them)

The omit keyword shall only be used for optional fields

all fields in the structure shall be specified either with a value, the not used symbol "" or the omit keyword

The first component of the list (a value, a "-" or omit) is associated with the first field, the second list component is associated with the second field etc

When all remaining fields at the end of the type definition are optional and they are wished to be omitted by the implicit mechanism, either the not used symbol "-" can be used for some or all of them

optional fields wished to be omitted by the implicit mechanism, but followed by fields to which a value or template is assigned explicitly, shall be skipped by using the not used symbol "-"

or they can simply be left out from the notation.

Fields or elements not mentioned are implicitly left uninitialized

It is also possible to leave fields explicitly unspecified using the not used symbol "-"

When re-assigning a previously initialized value, using the not used symbol or just skipping a field or element in an assignment notation, will cause that field or element to remain unchanged.

fields, not explicitly referred to in the notation, shall remain unchanged

In particular, when specifying partial values (i.e. setting the value of only a subset of the fields) using the assignment notation, for example, at initialization, only the fields or elements to be assigned values shall be specified