Datatypes R2 Issue 67

Need to document what the acceptable constraint rules are for datatypes.

This table summarizes the allowable datatype substitutions in designs. Note that regards to collections, COLL<X> can by constrained to COLL<Y> where Y is a valid constraint on X.

The second table is those proposed by Lloyd, but no formal basis:

Source	Allowed
ANY	anything (including mixins?)
BL	nothing
BN	nothing
ED	ST
ST	UID
CD	CE, CV, CO
CE	CV, CO
CV	CO
CO	nothing
CS	nothing
CR	nothing
SC	nothing
II	nothing
TEL	nothing
AD	nothing
EN	PN, ON, TN
PN	nothing
TN	nothing
ON	nothing
QTY	TS, MO, REAL, INT, TS, RTO<QTY, QTY>, PQ
INT	nothing
REAL	nothing
RTO	nothing
PQ	nothing
PQR	nothing
MO	nothing
TS	nothing
SET<T>	T
LIST<T>	T
GLIST<T>	T
SLIST<T>	T
BAG<T>	T
IVL<T>	T
HIST<T>	HXIT<T>, T
UVP<T>	T
NPPD<T>	T
PIVL<T>	nothing
EIVL<T>	nothing
GTS<T>	SET<PIVL<TS>>, SET<EIVL<TS>>
PPD<T>	?

Source	Allowed
SC	ST
PN	TN
ON	TN
REAL	INT
PQ	REAL
BAG	SET, LIST
PIVL<T>	IVL<TS>