stanfordnlp/CoreNLP · error · RuntimeException

Coordination node must have at least 2 children.

Error message

Coordination node must have at least 2 children.

What it means

The CoordinationPattern constructor throws RuntimeException when fewer than 2 child patterns are supplied. A coordination node in a Semgrex pattern represents AND/OR of sub-patterns, which is meaningless with 0 or 1 children.

Solutions

1. Ensure at least 2 child SemgrexPatterns exist before constructing a CoordinationPattern
2. If only one child, use the child pattern directly instead of wrapping it in a coordination
3. Fix the pattern parser/builder so single-branch coordinations are simplified away

Example fix

// before
new CoordinationPattern(isNodeCoord, Collections.singletonList(child), isConj, isRoot);
// after
SemgrexPattern pattern = children.size() == 1 ? children.get(0)
    : new CoordinationPattern(isNodeCoord, children, isConj, isRoot);

if (children == null || children.size() < 2) throw new IllegalArgumentException("CoordinationPattern needs >= 2 children");

try { SemgrexPattern p = new CoordinationPattern(isNodeCoord, children, isConj, isRoot); } catch (RuntimeException e) { fallback = children.size() == 1 ? children.get(0) : null; }

When it happens

Trigger: Constructing new CoordinationPattern(isNodeCoord, listOfOnePattern, isConj, isRoot) with a list of size 0 or 1 — usually when a parser or builder collects children programmatically and only one alternative was found.

Common situations: Programmatic Semgrex pattern construction from configuration or grammar files where a coordination clause has a single branch; parser bug that drops duplicate children.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• Cannot process a single key/value from annotation as it is…
• Child should only be set on a UniqPattern at creation time
• Duplicate attribute found in semgrex expression
• ERROR: Invalid syntax in macro line: ""!
• Error parsing semgrex pattern

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/0b7e5987f36ad759. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/semgraph/semgrex/CoordinationPattern.java:33

  private static Redwood.RedwoodChannels log = Redwood.channels(CoordinationPattern.class);

  private static final long serialVersionUID = -3122330899634961002L;
  private final boolean isConj;
  private final boolean isNodeCoord;
  /**
   * Represents whether this is the root coordination.  If so, the
   * children have a higher operation priority, as the : operator is
   * the lowest precedence possible.
   */
  private final boolean isRoot;
  private final List<SemgrexPattern> children;

  /* if isConj is true, then it is an "AND" ; if it is false, it is an "OR".*/
  /* if isNodeCoord is true, then it is a node coordination conj; if it is false, then
           * 	it is a relation coordination conj. */
  public CoordinationPattern(boolean isNodeCoord, List<SemgrexPattern> children, boolean isConj, boolean isRoot) {
    if (children.size() < 2) {
      throw new RuntimeException("Coordination node must have at least 2 children.");
    }
    this.children = Collections.unmodifiableList(children);
    this.isConj = isConj;
    this.isNodeCoord = isNodeCoord;
    this.isRoot = isRoot;
  }

  public boolean isNodeCoord() { return isNodeCoord; }

  @Override
  public void setChild(SemgrexPattern child) {
    if (isNodeCoord) {
      for (Object c : children) {
        if (c instanceof NodePattern)
          ((NodePattern)c).setChild(child);
      }
    } else {

View on GitHub (pinned to 1b7edd19c4)