Retraces and Repetitions

Status: Current Last updated: 2026-05-11 23:16 EDT

Retraces mark content that the speaker said but then corrected, repeated, or abandoned. They are one of the most consequential constructs in CHAT because they affect how every dependent tier aligns to the main tier.

CHAT Syntax

A retrace has two parts: the retraced content (what the speaker said first) and the correction (what follows). The retraced content is marked with a trailing bracket code:

Single-Word Retraces

When only one word is retraced, no angle brackets are needed:

*CHI: I [/] I want that .
*CHI: ana [//] an .
*MOT: the book [/-] the magazine is here .

Group Retraces

When multiple words are retraced, angle brackets delimit the scope:

*MOT: <the dog> [//] the cat ran .
*CHI: <I want> [/] I need cookie .
*CHI: <I want the> [///] give me that .

Retraces with Replacements

A retraced word often has a replacement [: target] and/or error code [* code]. This is common in aphasia and child language corpora where the speaker produces an incorrect form:

*PAR: tika@u [: kitty] [* p:n] [//] kitty is nice .
%mor: noun|kitty aux|be-Fin-Ind-Pres-S3 adj|nice-S1 .

*PAR: lɛɾɪ@u [: later] [* p:n] [//] later in the day .
%mor: adv|late adp|in det|the-Def-Art noun|day .

*CHI: male [: female] [* s:r] [/] male [: female] [* s:r] .
%mor: adj|female-S1 .

In each case, the retraced word (before the [//] or [/]) is excluded from %mor alignment. Only the correction (after the marker) is counted.

Data Model

Retraces are a first-class variant of UtteranceContent:

flowchart TD
    UC["UtteranceContent"]
    UC --> Word
    UC --> RW["ReplacedWord"]
    UC --> Retrace
    UC --> AG["AnnotatedGroup"]
    UC --> Other["...20 other variants"]

    Retrace --> BC["BracketedContent"]
    Retrace --> RK["RetraceKind"]
    BC --> BIW["BracketedItem::Word"]
    BC --> BIRW["BracketedItem::ReplacedWord"]

    style Retrace fill:#f96,stroke:#333

The Retrace struct wraps the retraced content in a BracketedContent container, which can hold any combination of words, replaced words, and other content items:

// crates/talkbank-model/src/model/content/retrace.rs
pub struct Retrace {
    pub content: BracketedContent,          // the retraced words
    pub kind: RetraceKind,                  // Partial, Full, Multiple, Reformulation
    pub is_group: bool,                     // <word> [/] vs word [/]
    pub annotations: Vec<ContentAnnotation>,// non-retrace annotations after marker
    pub span: Span,
}

Why First-Class?

Before the retrace refactor, retraces were represented as annotations on words or groups. This meant every match on content had to inspect annotation lists to determine whether a word was retraced. This led to a class of bugs where retraced content was accidentally included in alignment counting, word extraction, or retokenization.

Making Retrace a top-level UtteranceContent variant means:

1. The compiler enforces handling. Every match on UtteranceContent must have a Retrace arm. Forgetting to handle retraces is a compile error, not a silent runtime bug.
2. Domain-aware gating is centralized. The content walker checks the Retrace variant once, not at every annotation-inspection site.
3. Alignment counting is simple. The count function returns 0 for Retrace in Mor domain, no annotation inspection needed.

Parser Conversion

The tree-sitter grammar parses retrace markers ([/], [//], etc.) as annotations on word_with_optional_annotations. The Rust parser converts them to structural Retrace nodes in parse_word_content():

flowchart LR
    subgraph "Tree-sitter CST"
        WOA["word_with_optional_annotations"]
        SW["standalone_word"]
        BA["base_annotations"]
        RP["retrace_partial / retrace_complete / ..."]
        WOA --> SW
        WOA --> BA
        BA --> RP
    end

    subgraph "Rust Model"
        RET["UtteranceContent::Retrace"]
        BC2["BracketedContent"]
        W2["Word or ReplacedWord"]
        RET --> BC2
        BC2 --> W2
    end

    WOA -->|"parse_word_content()\n(word.rs)"| RET

Three cases in parse_word_content():

1. Word + retrace (I [/]), wrap Word in BracketedItem::Word inside Retrace
2. Word + replacement + retrace (tika@u [: kitty] [* p:n] [//]), build ReplacedWord, then wrap in BracketedItem::ReplacedWord inside Retrace
3. Word + replacement, no retrace (tika@u [: kitty]), emit bare ReplacedWord

Group retraces (<content> [/]) are handled in group/parser.rs via the same structural wrapping.

Alignment Behavior

Retraces interact differently with each dependent tier domain:

flowchart TD
    RT["Retrace node\n(e.g. 'tika@u [: kitty] [* p:n] [//]')"]

    RT -->|"Mor domain"| SKIP["SKIP\n(return 0)\nNot morphologically analyzed"]
    RT -->|"Pho domain"| COUNT["COUNT\nPhonologically produced"]
    RT -->|"Sin domain"| COUNT2["COUNT\nGesturally produced"]
    RT -->|"Wor domain"| COUNT3["RECURSE\napply retrace-aware %wor leaf rule"]

    style SKIP fill:#faa,stroke:#333
    style COUNT fill:#afa,stroke:#333
    style COUNT2 fill:#afa,stroke:#333
    style COUNT3 fill:#afa,stroke:#333

Why %mor skips retraces: The %mor tier represents the morphological analysis of what the speaker meant to say. Retraced content is a false start or error; it was produced phonologically but is not part of the intended linguistic structure. The correction after the retrace marker carries the morphological analysis.

Why %pho/%sin/%wor include retraces: These tiers document what was actually produced, the sounds, gestures, and timing of the speech as it happened, including false starts. The retrace was physically spoken, so it appears in these tiers.

For %wor, retrace ancestry does not change leaf-level membership:

• spoken word tokens count both inside and outside retrace
• that includes fillers, fragments, nonwords, and untranscribed placeholders
• overlap annotations do not affect %wor membership

Exact corpus-shaped contrast:

*CHI:	<one &+ss> [/] one play ground .
%wor:	one •321008_321148• ss •321148_321368• one •321809_321969• play •322049_322310• ground •322390_322890• .

*CHI:	&+ih <the what> [/] what's letter &+th is this ?
%wor:	ih •49063_49103• the •49103_49163• what •49183_50205• what's •50205_50405• letter •50405_50685• th •50886_50946• is •50946_51046• this •51086_51586• ?

Implementation

Counting: count_alignable_item() in alignment/helpers/count.rs:

UtteranceContent::Retrace(retrace) => {
    if domain == TierDomain::Mor {
        0  // excluded from morphological alignment
    } else {
        count_bracketed_alignable_content(&retrace.content, domain, true)
    }
}

Walking: walk_words() in alignment/helpers/walk/mod.rs:

UtteranceContent::Retrace(retrace) => {
    if !matches!(domain, Some(TierDomain::Mor)) {
        walk_bracketed_content(&retrace.content.content, domain, f);
    }
}

%wor generation and overlap counting still use dedicated recursive helpers, but now for %wor-specific sequencing details like replacement handling rather than for retrace-sensitive membership.

Validation

Cross-Utterance Retrace Validation

The retrace validators in validation/retrace/ check:

• Collection: collection/utterance.rs and collection/bracketed.rs walk the content tree to find all Retrace nodes
• Detection: detection.rs provides utterance_item_has_retrace() for quick retrace presence checks

Alignment Validation (E705)

E705 fires when the main tier has more alignable items than %mor. If retraces are correctly parsed as Retrace nodes; they are excluded from the count and E705 does not fire. If a retrace is accidentally parsed as a bare ReplacedWord (the bug fixed in c90b9bf), it is counted and triggers a false E705.

Regression Tests

tests/retrace_replaced_word_regression.rs contains 6 targeted tests:

Reference corpus entries: corpus/reference/annotation/retrace.cha

See Also

• Alignment Architecture: full alignment system docs
• The %mor Tier: morphological tier format and alignment rules
• CHAT Manual: Retracing