Re: Relation Definition

>> No, that cannot be right because it would allow the same attribute name
>> to appear more than once.

Why so? The header is a set -- so the elements i.e. the named typed attributes in a set are unique. When one ignores the typed perspective, the header is simply a set of column names, again being a set, the elements must be distinct.

If the uniqueness of attribute names were not made explicit is your concern, the definition of the header in a relation is stated as: Given a collection of n types or domains Ti ( I = 1, 2, ...n ), not necessarily distinct, r is a relation on those types if it consists of two parts, a heading and a body, where the heading is a set of n attributes of the form Ai:Ti, where Ai ( which must all be distinct) are the attributes names of r and the Ti are corresponding type names ( i = 1,2,...n )

>> http://mathworld.wolfram.com/n-Tuple.html

That provides a possible vector interpretation of an n-Tuple. Nothing in that reference suggests the notion of n-dimensional tuple is usually reserved for ordered tuples and is inappropriate elsewhere.

-- 
Anith