This document describes the validation rules for names in Groot2 and BehaviorTree.CPP. These rules ensure XML compatibility while supporting Unicode characters (Chinese, Japanese, Korean, etc.).

The validation uses a blacklist approach: all characters are allowed except those explicitly forbidden. This enables Unicode support while blocking characters that would break XML serialization or cause path/filesystem issues.

The following ASCII characters are forbidden in Model Names and Port Names:

• Cannot be empty
• Cannot be "Root" (reserved)
• No forbidden characters (see table above)

• Cannot be empty
• Cannot start with a digit
• Cannot be a reserved attribute: ID, name, _description, _skipIf, _successIf, _failureIf, _while, _onSuccess, _onFailure, _onHalted, _post, _autoremap, __shared_blackboard
• No forbidden characters (see table above)

• Can be empty (defaults to model name)
• Instance names are XML attribute values (not element/attribute names), so most characters are allowed including spaces, periods, etc.
• Only invalid XML control characters are forbidden (ASCII 0-8, 11-12, 14-31, 127)

#include <algorithm>
#include <array>
#include <string>

// Returns the forbidden character if found, or '\0' if valid
static char findForbiddenChar(const std::string& name)
{
  static constexpr std::array<char, 16> forbidden = {
      ' ', '\t', '\n', '\r', '<', '>', '&', '"', '\'', '/', '\\', ':', '*', '?', '|', '.'};

  for (unsigned char c : name)
  {
    // Allow UTF-8 multibyte sequences (high bit set)
    if (c >= 0x80)
    {
      continue;
    }
    // Block control characters
    if (c < 32 || c == 127)
    {
      return static_cast<char>(c);
    }
    // Check forbidden list
    if (std::find(forbidden.begin(), forbidden.end(), c) != forbidden.end())
    {
      return static_cast<char>(c);
    }
  }
  return '\0';
}

MyAction
my_action
My-Action
检查门状态      (Chinese)
ドアを開ける    (Japanese)
Tür_öffnen      (German)

My Action       (contains space)
request.name    (contains period)
My<Node>        (contains XML chars)
path/to/node    (contains path separator)
Root            (reserved)

Instance names have relaxed rules since they are XML attribute values:

My Action           (spaces allowed)
node.name           (periods allowed)
Success 1           (spaces allowed)
检查门状态          (Unicode allowed)

name_with_null\0    (null character)
name_with_bell\x07  (control character)

• #59 - Unicode support in node names
• #60 - i18n support request
• #64 - Clear error for forbidden characters in port names

• include/behaviortree_cpp/basic_types.h - findForbiddenChar() declaration
• src/basic_types.cpp - findForbiddenChar() implementation, IsAllowedPortName() update
• src/xml_parsing.cpp - Validation functions and integration in XML parsing
• tests/gtest_name_validation.cpp - Comprehensive tests for validation