ETCD (the short form of ELEMENT) is limited to 8 characters and does not have special character restrictions.
Req
ELEMENT
Description of Element
Char
...
Synonym Qualifier
The name of the Element.
Req
TESTRL
Rule for Start of Element
Char
...
Rule
Expresses rule for beginning Element.
Req
TEENRL
Rule for End of Element
Char
...
Rule
Expresses rule for ending Element. Either TEENRL or TEDUR must be present for each Element; both may be present.
Perm
TEDUR
Planned Duration of Element
Char
ISO 8601 duration
Timing
Planned duration of Element in ISO 8601 format. Use when an Element represents a fixed duration. TEENRL or TEDUR must be present for each Element; both may be present.