Piece Identifier Notation (PIN) Specification

Version: 1.0.0
Author: Sashité
Published: June 23, 2025
License: MIT License

Overview

Piece Identifier Notation (PIN) provides an ASCII-based format for representing pieces in abstract strategy board games. PIN translates piece attributes from the Game Protocol into a compact, portable notation system.

PIN represents three of the four fundamental piece attributes:

Type + Side → Single ASCII letter with case encoding
State → Optional prefix modifier

Note: PIN does not represent the Style attribute. For style-aware piece notation, see Piece Name Notation (PNN).

Format Specification

Structure

[<state>]<letter>

Grammar (BNF)

<pin> ::= <letter>
       | <state-modifier> <letter>

<state-modifier> ::= "+" | "-"
<letter> ::= <uppercase-letter> | <lowercase-letter>

<uppercase-letter> ::= "A" | "B" | "C" | ... | "Z"
<lowercase-letter> ::= "a" | "b" | "c" | ... | "z"

Regular Expression

\A[-+]?[A-Za-z]\z

Protocol Mapping

PIN encodes piece attributes using the following correspondence:

Protocol Attribute	PIN Encoding	Examples
Type	ASCII letter choice	`K`/`k` = King, `P`/`p` = Pawn
Side	Letter case	`K` = First player, `k` = Second player
State	Optional prefix	`+K` = Enhanced, `-K` = Diminished, `K` = Normal

Canonical principle: Identical pieces must have identical PIN representations.

System Constraints

Type Limitation

PIN supports a maximum of 26 unique piece types per game system. Each type requires a distinct ASCII letter.

Examples:

Chess (6 types): Well within limits
Shōgi (8 base types): Manageable with state modifiers
Taikyoku Shōgi (207 types): Exceeds PIN capacity

Player Limitation

PIN supports exactly two players through case distinction:

First player: Uppercase letters (A-Z)
Second player: Lowercase letters (a-z)

State Levels

PIN provides three state levels:

Enhanced (+): Promoted, upgraded, or empowered pieces
Normal (no modifier): Standard piece state
Diminished (-): Weakened, restricted, or temporary pieces

Design Properties

ASCII compatibility: Maximum portability across systems
Rule-agnostic: Independent of specific game mechanics
Compact format: Minimal character usage (1-2 characters per piece)
Visual distinction: Clear player differentiation through case
Protocol compliance: Direct implementation of Sashité piece attributes

Implementation

Ruby Reference

Pin.rb – Reference implementation with full protocol compliance validation.

Practical Examples

Comprehensive implementation examples for chess, shōgi, and other games are available in the PIN Examples Documentation.