stanfordnlp/CoreNLP · error · java.lang.Error

Unknown sequence pattern variable

Error message

Unknown sequence pattern variable 

What it means

SeqVar resolves a REGEXVAR token (a '$name' reference) to a previously registered SequencePattern.PatternExpr in the parse environment. If env.getSequencePatternExpr(name.image, true) returns null, the parser throws 'Unknown sequence pattern variable <name>' because the referenced pattern variable was never defined in the environment.

Solutions

1. Define the referenced variable before use, e.g. with a rule like 'pattern = ( ... )' or env.bind(name, patternExpr) in code.
2. Check exact name and case match between the definition and the $reference.
3. Load all variable-defining rule files into the same Env before parsing dependent rules.
4. Log env contents (or iterate bound names) to confirm which sequence pattern variables exist.

Example fix

// before
String rule = "$DATE"; // never defined
// after
env.bind("DATE", datePattern); // or add: $DATE = ( [ { tag:/DATE/ } ] )\n... $DATE ...

// Confirm all $refs used in a rule are defined in the Env first
Set<String> defined = env variable names; // collect via your binding registry
java.util.regex.Matcher m = java.util.regex.Pattern.compile("\\$([A-Za-z_]\\w*)").matcher(ruleText);
while (m.find()) {
  if (!defined.contains(m.group(1))) throw new IllegalStateException("Undefined variable: " + m.group(1));
}

try {
  return parser.parsePattern(env, ruleText);
} catch (Error e) {
  if (e.getMessage() != null && e.getMessage().startsWith("Unknown sequence pattern variable")) {
    throw new IllegalArgumentException(e.getMessage() + " - define it via a pattern rule or env.bind() first", e);
  }
  throw e;
}

When it happens

Trigger: Parsing a TokensRegex sequence pattern whose text references $VarName, but no pattern of that name was registered in the Env (e.g. via env.bind or sequence pattern definitions) before parsing.

Common situations: Rule files where the variable definition rule was removed, renamed, or where variables are defined in a separate file not loaded into the same environment; also case-sensitivity mismatches between definition and reference.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

• Unknown sequence pattern variable
• Attribute match already defined
• Attribute already defined
• Field already defined:
• Attribute match already defined:

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/d4e133c1b866f89d. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/ling/tokensregex/parser/TokenSequenceParser.java:1287

        jj_consume_token(32);
        break;
        }
      default:
        jj_la1[40] = jj_gen;
        jj_consume_token(-1);
        throw new ParseException();
      }
    }
{if ("" != null) return node;}
    throw new Error("Missing return statement in function");
}

  final public SequencePattern.PatternExpr SeqVar(Env env) throws ParseException {SequencePattern.PatternExpr expr;
  Token name;
    name = jj_consume_token(REGEXVAR);
expr = env.getSequencePatternExpr(name.image, true);
        if (expr == null) {
            {if (true) throw new Error("Unknown sequence pattern variable " + name.image);}
        }
{if ("" != null) return expr;}
    throw new Error("Missing return statement in function");
}

  final public SequencePattern.PatternExpr SeqBackRef(Env env) throws ParseException {Token name;
    name = jj_consume_token(BACKREF);
int v = Integer.parseInt(name.image.substring(1));
        {if ("" != null) return new SequencePattern.BackRefPatternExpr(CoreMapNodePattern.TEXT_ATTR_EQUAL_CHECKER, v);}
    throw new Error("Missing return statement in function");
}

  final public NodePattern Node(Env env) throws ParseException {NodePattern node;
    switch ((jj_ntk==-1)?jj_ntk_f():jj_ntk) {
    case 31:{
      node = BracketedNode(env);
      break;
      }

View on GitHub (pinned to 1b7edd19c4)