A notation of the form was introduced last time to indicate a category of grammatical relationships whose sense is suggested by any of the following readings.

For the moment it’s enough to call a covering relation, reading it as

In what follows the letter indicates the type of a sentence in the contemplated language   The letter is the initial symbol or sentence symbol of the candidate formal grammar for

Generally speaking, any number of letters like signifying other types of strings, will be found necessary for a reasonable account or rational reconstruction of the sentences in   The additional letters are known as intermediate symbols and collected together in the set

Combining the singleton set whose sole member is the initial symbol with the set of intermediate symbols results in the set of non‑terminal symbols.  Even though is strictly only the set of intermediate symbols, it is handy to use as a typical variable ranging over the full set of non‑terminal symbols,

To complete the package, the alphabet of the language may also be referred to as the set of terminal symbols.

Resources

• Cactus Language • Preliminaries
• Survey of Animated Logical Graphs
• Survey of Theme One Program

cc: Academia.edu • BlueSky • Laws of Form • Ma^thstodon • Research Gate
cc: Conceptual Graphs • Cybernetics • Structural Modeling • Systems Science