We extend display form names to include the form "OBname.foo" where "foo" is a string other than a decimal numeral. By including "Name:foo" as an attribute of a display form spec, the user introduces an alias for that display form. This makes the precedence system less sensitive to the order of specs in a display object.
But when the string is empty, the name, e.g. "OBname.", is just an abbreviation for "OBname.1", the first form in the object.

We also introduce "precedence class names" which are like display form names, except the object name position is filled by the empty string, e.g., ".foo". The string should be chosen as a convenient mnemonic for a precedence class the user has in mind. We'll see how these are used below.

It will simplify our explanation of precedence classes if we introduce a similar relation on the display names together with the variations introduced above. Let's call this relation "precedence", too. Then, we shall say two display forms have the same precedence when their standard display names (of form "OBname.n") have the same precedence.

How precedence classes are determined. Below we'll use

"OBname"	to range over possible object names,
"n"	to range over decimal numerals,
"foo"	to range over non-empty strings other than decimal numerals, and
"X" and "Y"	to range over all strings.

Sameness of precedence is the strongest equivalence relation "<df>=<df>" such that:

OBname.=OBname.1
OBname.foo=OBname.n	if the n-th display spec of the DISP OBname has the attribute Name:foo
OBname.X=OBname.n	if the n-th display spec of the DISP OBname has the attribute =X
OBname.1=OBname.n	if the n-th display spec of the DISP OBname has the attribute =FIRST
X.Y=OBname.n	if the n-th display spec of the DISP OBname has the attribute =X.Y
X1.Y1=X2.Y2	if X1.Y1 and X2.Y2 occur in the same <df>=<df> sequence within some LAT object