A readable exchange can contain different intellectual operations. One contribution explains an idea. Another illustrates a distinction, answers an objection, or explores implications. DiGraph proposes short, explicitly defined symbols for marking such concepts in an exchange.

The surrounding explanation remains in ordinary language. A symbol makes the intended kind of contribution explicit. Early examples should include the full meaning of the symbol so that readers and models can interpret the proposal.

A symbol contains exactly two characters. Letters, digits, whitespace, underscores, backslashes, and all brackets are excluded. The bracket restriction includes angle brackets. Mnemonic associations are optional. The accepted spellings are ## and ;;. The additional assignments presented here are proposals.