diff --git a/bids/validator/sidecarValidator.js b/bids/validator/sidecarValidator.js
index 0fbfc3b6..790c23fb 100644
--- a/bids/validator/sidecarValidator.js
+++ b/bids/validator/sidecarValidator.js
@@ -48,12 +48,11 @@ export class BidsHedSidecarValidator extends BidsValidator {
     for (const [sidecarKeyName, hedData] of this.bidsFile.parsedHedData) {
       if (hedData instanceof ParsedHedString) {
         // Value options have HED as string.
-        issues.push(...this._checkDetails(sidecarKeyName, hedData, true))
+        issues.push(...this._checkDetails(sidecarKeyName, hedData))
       } else if (hedData instanceof Map) {
         // Categorical options have HED as a Map.
         for (const valueString of hedData.values()) {
-          const placeholdersAllowed = this.bidsFile.sidecarKeys.get(sidecarKeyName).hasDefinitions
-          issues.push(...this._checkDetails(sidecarKeyName, valueString, placeholdersAllowed))
+          issues.push(...this._checkDetails(sidecarKeyName, valueString))
         }
       } else {
         IssueError.generateAndThrow('internalConsistencyError', {
diff --git a/common/issues/data.js b/common/issues/data.js
index 083250e3..4457edb6 100644
--- a/common/issues/data.js
+++ b/common/issues/data.js
@@ -277,7 +277,7 @@ export default {
   tooManyGroupTopTags: {
     hedCode: 'TAG_GROUP_ERROR',
     level: 'error',
-    message: stringTemplate`Group "${'string'}" has too many or too few tags at the top level.`,
+    message: stringTemplate`Group "${'string'}" has too many or too few tags or Def-expand groups at the top level.`,
   },
   multipleTopLevelTagGroupTags: {
     hedCode: 'TAG_GROUP_ERROR',
diff --git a/data/json/reservedTags.json b/data/json/reservedTags.json
index 614c68d5..f4d95d07 100644
--- a/data/json/reservedTags.json
+++ b/data/json/reservedTags.json
@@ -141,7 +141,7 @@
     "forbiddenSubgroupTags": [],
     "isTemporalTag": true,
     "requiresDef": true,
-    "otherAllowedNonDefTags": ["Def", "Delay"]
+    "otherAllowedNonDefTags": ["Delay"]
   },
   "Onset": {
     "name": "Onset",
diff --git a/parser/definitionManager.js b/parser/definitionManager.js
index ce2328a4..83d4b934 100644
--- a/parser/definitionManager.js
+++ b/parser/definitionManager.js
@@ -1,6 +1,5 @@
 import { generateIssue, IssueError } from '../common/issues/issues'
 import { parseHedString } from './parser'
-//import { filterNonEqualDuplicates } from './parseUtils'
 import { filterByTagName } from './parseUtils'
 
 export class Definition {
@@ -219,7 +218,7 @@ export class DefinitionManager {
   }
 
   /**
-   * Evaluate the definition based on a parsed HED tag
+   * Evaluate the definition based on a parsed HED tag.
    * @param {ParsedHedTag} tag - The tag to evaluate against the definitions.
    * @param {Schemas} hedSchemas - The schemas to be used to assist in the evaluation.
    * @param {boolean} placeholderAllowed - If true then placeholder is allowed in the def tag.
diff --git a/parser/parseUtils.js b/parser/parseUtils.js
index ea9e4a0d..8b70896c 100644
--- a/parser/parseUtils.js
+++ b/parser/parseUtils.js
@@ -44,20 +44,6 @@ export function filterTagMapByNames(tagMap, tagNames) {
   return keys.flatMap((key) => tagMap.get(key))
 }
 
-/*/!**
- * Extract the ParsedHedTag tags that have a name from a specified list of names
- * @param {ParsedHedTag[]} tags - to be filtered by name
- * @param {[string]} tagList - List of tag names to filter by.
- * @returns {ParsedHedTag[]} - A list of tags whose
- *!/
-
-export function filterByTagNames(tags, tagList) {
-  if (!tags || !tagList) {
-    return []
-  }
-  return tags.filter((tag) => tagList.includes(tag.schemaTag.name))
-}*/
-
 /**
  * Convert a list of ParsedHedTag objects into a comma-separated string of their string representations.
  * @param {ParsedHedTag []} tagList - The HED tags whose string representations should be put in a comma-separated list.
@@ -68,10 +54,10 @@ export function getTagListString(tagList) {
 }
 
 /**
- * Create a map of the ParsedHedTags by type
- * @param { ParsedHedTag[] } tagList
- * @param {Set} tagNames
- * @returns {Map<string, ParsedHedTag[]>}
+ * Create a map of the ParsedHedTags by type.
+ * @param { ParsedHedTag[] } tagList - The HED tags to be categorized.
+ * @param {Set} tagNames - The tag names to use as categories.
+ * @returns {Map<string, ParsedHedTag[]>} - A map of tag name to a list of tags with that name.
  */
 export function categorizeTagsByName(tagList, tagNames = null) {
   // Initialize the map with keys from tagNames and an "other" key
@@ -89,9 +75,9 @@ export function categorizeTagsByName(tagList, tagNames = null) {
 }
 
 /**
- * Return a list of duplicate strings
- * @param { string[] } itemList - A list of strings to look for duplicates in
- * @returns {string []} - a list of unique duplicate strings (multiple copies not repeated
+ * Return a list of duplicate strings.
+ * @param { string[] } itemList - A list of strings to look for duplicates in.
+ * @returns {string []} - a list of unique duplicate strings (multiple copies not repeated.
  */
 export function getDuplicates(itemList) {
   const checkSet = new Set()
diff --git a/parser/parsedHedGroup.js b/parser/parsedHedGroup.js
index 35590c55..0212b4e9 100644
--- a/parser/parsedHedGroup.js
+++ b/parser/parsedHedGroup.js
@@ -19,23 +19,41 @@ import {
  */
 export default class ParsedHedGroup extends ParsedHedSubstring {
   /**
-   * The parsed HED tags or parsedHedGroups or parsedColumnSplices in the HED tag group at the top level
+   * The parsed HED tags, groups, or splices in the HED tag group at the top level.
    * @type {ParsedHedSubstring[]}
    */
   tags
 
+  /**
+   * The top-level parsed HED tags in this string.
+   * @type {ParsedHedTag[]}
+   */
   topTags
 
+  /**
+   * The top-level parsed HED groups in this string.
+   * @type {ParsedHedGroup[]}
+   */
   topGroups
 
+  /**
+   * The top-level column splices in this string
+   * @type {ParsedHedColumnSplice[]}
+   */
   topSplices
 
+  /**
+   * All the parsed HED tags in this string.
+   * @type {ParsedHedTag[]}
+   */
   allTags
+
   /**
-   * Any HED tags with special handling. This only covers top-level tags in the group
+   * Any HED tags with special handling. This only covers top-level tags in the group.
    * @type {Map<string, ParsedHedTag[]>}
    */
   specialTags
+
   /**
    * Whether this HED tag group has child groups with a Def-expand tag.
    * @type {boolean}
@@ -48,12 +66,28 @@ export default class ParsedHedGroup extends ParsedHedSubstring {
    */
   defExpandChildren
 
+  /**
+   * True if this group has a Def-expand tag at the top level.
+   * @type {boolean}
+   */
   isDefExpandGroup
 
+  /**
+   * True if this group has a Definition tag at the top level.
+   * @type {boolean}
+   */
   isDefinitionGroup
 
+  /**
+   * The total number of top-level Def tags and top-level Def-expand groups.
+   * @type {Number}
+   */
   defCount
 
+  /**
+   * The unique top-level tag requiring a Def or Def-expand group, if any.
+   * @type {ParsedHedTag | null}
+   */
   requiresDefTag
 
   /**
@@ -74,11 +108,20 @@ export default class ParsedHedGroup extends ParsedHedSubstring {
     this._initializeGroups()
   }
 
+  /**
+   * Recursively create a list of all the tags in this group.
+   * @returns {ParsedHedTag[]}
+   * @private
+   */
   _getAllTags() {
     const subgroupTags = this.topGroups.flatMap((tagGroup) => tagGroup.allTags)
     return this.topTags.concat(subgroupTags)
   }
 
+  /**
+   * Sets information about the special tags, particularly definition-related tags in this group.
+   * @private
+   */
   _initializeGroups() {
     const special = ReservedChecker.getInstance()
     this.specialTags = categorizeTagsByName(this.topTags, special.specialNames)
@@ -91,10 +134,11 @@ export default class ParsedHedGroup extends ParsedHedSubstring {
   }
 
   /**
-   * Filter top subgroups that include a special at the top-level of the group
+   * Filter top subgroups that include a special at the top-level of the group.
    *
    * @param {string} tagName - The schemaTag name to filter by.
    * @returns {Array} - Array of subgroups containing the specified tag.
+   * @private
    */
   _filterSubgroupsByTagName(tagName) {
     return Array.from(this.topLevelGroupIterator()).filter((subgroup) => subgroup.specialTags.has(tagName))
@@ -147,18 +191,6 @@ export default class ParsedHedGroup extends ParsedHedSubstring {
     return this.specialTags.get(tagName) ?? []
   }
 
-  isSpecialGroup(tagName) {
-    return this.specialTags.has(tagName)
-  }
-
-  /**
-   * Whether this HED tag group is an onset, offset, or inset group.
-   * @returns {boolean}
-   */
-  get isTemporalGroup() {
-    return this.isSpecialGroup('Onset') || this.isSpecialGroup('Offset') || this.isSpecialGroup('Inset')
-  }
-
   get defTags() {
     const tags = this.getSpecial('Def')
     for (const group of this.defExpandChildren) {
@@ -178,22 +210,6 @@ export default class ParsedHedGroup extends ParsedHedSubstring {
     )
   }
 
-  /**
-   * The deeply nested array of parsed tags.
-   * @returns {ParsedHedTag[]}
-   */
-  nestedGroups() {
-    const groups = []
-    for (const innerTag of this.tags) {
-      if (innerTag instanceof ParsedHedTag) {
-        groups.push(innerTag)
-      } else if (innerTag instanceof ParsedHedGroup) {
-        groups.push(innerTag.nestedGroups())
-      }
-    }
-    return groups
-  }
-
   /**
    * Return a normalized string representation
    * @returns {string}
@@ -220,20 +236,6 @@ export default class ParsedHedGroup extends ParsedHedSubstring {
     return `(${sortedNormalizedItems.join(',')})` // Using curly braces to indicate unordered group
   }
 
-  /**
-   * Iterator over the full HED groups and subgroups in this HED tag group.
-   *
-   * @yields {ParsedHedTag[]} The subgroups of this tag group.
-   */
-  *subGroupArrayIterator() {
-    for (const innerTag of this.tags) {
-      if (innerTag instanceof ParsedHedGroup) {
-        yield* innerTag.subGroupArrayIterator()
-      }
-    }
-    yield this.tags
-  }
-
   /**
    * Iterator over the ParsedHedGroup objects in this HED tag group.
    * @param {string | null} tagName - The name of the tag whose groups are to be iterated over or null if all tags.
diff --git a/parser/parsedHedString.js b/parser/parsedHedString.js
index 3e4a5f7a..274a3d97 100644
--- a/parser/parsedHedString.js
+++ b/parser/parsedHedString.js
@@ -39,7 +39,7 @@ export class ParsedHedString {
    */
   columnSplices
   /**
-   * The top-level tag groups in the string, split into arrays.
+   * The tags in the top-level tag groups in the string, split into arrays.
    * @type {ParsedHedTag[][]}
    */
   topLevelGroupTags
diff --git a/parser/parsedHedTag.js b/parser/parsedHedTag.js
index c4f3ad20..8ad463ee 100644
--- a/parser/parsedHedTag.js
+++ b/parser/parsedHedTag.js
@@ -77,7 +77,6 @@ export default class ParsedHedTag extends ParsedHedSubstring {
     super(tagSpec.tag, tagSpec.bounds) // Sets originalTag and originalBounds
     this._convertTag(hedSchemas, hedString, tagSpec)
     this._normalized = this.format(false) // Sets various forms of the tag.
-    this._validUnits = null
   }
 
   /**
@@ -113,11 +112,12 @@ export default class ParsedHedTag extends ParsedHedSubstring {
   }
 
   /**
-   * Handle the remainder portion for value tag (converter handles others)
+   * Handle the remainder portion for value tag (converter handles others).
    *
-   * @param {SchemaTag} schemaTag - The part of the tag that is in the schema
-   * @param {string} remainder - the leftover part
+   * @param {SchemaTag} schemaTag - The part of the tag that is in the schema.
+   * @param {string} remainder - the leftover part.
    * @throws {IssueError} If parsing the remainder section fails.
+   * @private
    */
   _handleRemainder(schemaTag, remainder) {
     if (!(schemaTag instanceof SchemaValueTag)) {
@@ -149,10 +149,10 @@ export default class ParsedHedTag extends ParsedHedSubstring {
   }
 
   /**
-   * Separate the remainder of the tag into three parts:
+   * Separate the remainder of the tag into three parts.
    *
-   * @param {SchemaTag} schemaTag - The part of the tag that is in the schema
-   * @param {string} remainder - the leftover part
+   * @param {SchemaTag} schemaTag - The part of the tag that is in the schema.
+   * @param {string} remainder - The leftover part.
    * @returns {[SchemaUnit, string, string]} - The actual Unit, the unit string and the value string.
    * @throws {IssueError} If parsing the remainder section fails.
    */
@@ -206,6 +206,10 @@ export default class ParsedHedTag extends ParsedHedSubstring {
     }
   }
 
+  /**
+   * Return the normalized version of this tag.
+   * @returns {string} - The normalized version of this tag.
+   */
   get normalized() {
     return this._normalized
   }
@@ -233,82 +237,6 @@ export default class ParsedHedTag extends ParsedHedSubstring {
     return this.schema?.tagHasAttribute(this.formattedTag, attribute)
   }
 
-  /**
-   * Get the last part of a HED tag.
-   *
-   * @param {string} tagString A HED tag.
-   * @returns {string} The last part of the tag using the given separator.
-   */
-  static getTagName(tagString) {
-    const lastSlashIndex = tagString.lastIndexOf('/')
-    if (lastSlashIndex === -1) {
-      return tagString
-    } else {
-      return tagString.substring(lastSlashIndex + 1)
-    }
-  }
-
-  /**
-   * The trailing portion of {@link originalTag}.
-   *
-   * @returns {string} The "name" portion of the original tag.
-   */
-  get originalTagName() {
-    return ParsedHedTag.getTagName(this.originalTag)
-  }
-
-  /**
-   * Get the HED tag prefix (up to the last slash).
-   *
-   * @param {string} tagString A HED tag.
-   * @returns {string} The portion of the tag up to the last slash.
-   */
-  static getParentTag(tagString) {
-    const lastSlashIndex = tagString.lastIndexOf('/')
-    if (lastSlashIndex === -1) {
-      return tagString
-    } else {
-      return tagString.substring(0, lastSlashIndex)
-    }
-  }
-
-  /**
-   * Iterate through a tag's ancestor tag strings.
-   *
-   * @param {string} tagString - A tag string.
-   * @yields {string} - The tag's ancestor tags.
-   */
-  static *ancestorIterator(tagString) {
-    while (tagString.lastIndexOf('/') >= 0) {
-      yield tagString
-      tagString = ParsedHedTag.getParentTag(tagString)
-    }
-    yield tagString
-  }
-  /*
-
-  /!**
-   * Determine whether this tag is a descendant of another tag.
-   *
-   * @param {ParsedHedTag|string} parent The possible parent tag.
-   * @returns {boolean} Whether {@link parent} is the parent tag of this tag.
-   *!/
-  isDescendantOf(parent) {
-    if (parent instanceof ParsedHedTag) {
-      if (this.schema !== parent.schema) {
-        return false
-      }
-      parent = parent.formattedTag
-    }
-    for (const ancestor of ParsedHedTag.ancestorIterator(this.formattedTag)) {
-      if (ancestor === parent) {
-        return true
-      }
-    }
-    return false
-  }
-*/
-
   /**
    * Determine if this HED tag is equivalent to another HED tag.
    *
@@ -379,26 +307,6 @@ export default class ParsedHedTag extends ParsedHedSubstring {
     return []
   }
 
-  /**
-   * Get the legal units for this HED tag.
-   *
-   * @returns {Set<SchemaUnit>} The legal units for this HED tag.
-   */
-  get validUnits() {
-    if (this._validUnits) {
-      return this._validUnits
-    }
-    const tagUnitClasses = this.unitClasses
-    this._validUnits = new Set()
-    for (const unitClass of tagUnitClasses) {
-      const unitClassUnits = this.schema?.entries.unitClasses.getEntry(unitClass.name).units
-      for (const unit of unitClassUnits.values()) {
-        this._validUnits.add(unit)
-      }
-    }
-    return this._validUnits
-  }
-
   /**
    * Check if value is a valid value for this tag.
    *
diff --git a/parser/parser.js b/parser/parser.js
index c80a3174..4bc8bd9f 100644
--- a/parser/parser.js
+++ b/parser/parser.js
@@ -19,15 +19,23 @@ class HedStringParser {
    */
   hedSchemas
 
+  /**
+   * True if definitions are allowed in this string.
+   * @type {boolean}
+   */
   definitionsAllowed
 
+  /**
+   * True if placeholders are allowedare allowed in this string.
+   * @type {boolean}
+   */
   placeholdersAllowed
 
   /**
    * Constructor.
    *
-   * @param {string|ParsedHedString} hedString The HED string to be parsed.
-   * @param {Schemas} hedSchemas The collection of HED schemas.
+   * @param {string|ParsedHedString} hedString - The HED string to be parsed.
+   * @param {Schemas} hedSchemas - The collection of HED schemas.
    * @param {boolean} definitionsAllowed - True if definitions are allowed
    * @param {boolean} placeholdersAllowed - True if placeholders are allowed
    */
@@ -48,9 +56,7 @@ class HedStringParser {
     if (this.hedString === null || this.hedString === undefined) {
       return [null, [generateIssue('invalidTagString', {})]]
     }
-    // if (!this.hedString) {
-    //   return [null, []]
-    // }
+
     const placeholderIssues = this._getPlaceholderCountIssues()
     if (placeholderIssues.length > 0) {
       return [null, placeholderIssues]
@@ -157,7 +163,7 @@ export function parseHedString(hedString, hedSchemas, fullCheck, definitionsAllo
 /**
  * Parse a list of HED strings.
  *
- * @param {string[]|ParsedHedString[]} hedStrings A list of HED strings.
+ * @param {string[]|ParsedHedString[]} hedStrings - A list of HED strings.
  * @param {Schemas} hedSchemas - The collection of HED schemas.
  * @param {boolean} fullCheck - If the strings is in final form -- can be fully parsed
  * @param {boolean} definitionsAllowed - True if definitions are allowed
diff --git a/parser/reservedChecker.js b/parser/reservedChecker.js
index 606aa084..d77326ca 100644
--- a/parser/reservedChecker.js
+++ b/parser/reservedChecker.js
@@ -120,7 +120,7 @@ export class ReservedChecker {
    */
   checkTagGroupLevels(hedString, fullCheck) {
     const issues = []
-    const topGroupTags = hedString.topLevelGroupTags
+    const topGroupTags = hedString.topLevelGroupTags.flat()
     hedString.tags.forEach((tag) => {
       // Check for top-level violations because tag is deep
       if (ReservedChecker.hasTopLevelTagGroupAttribute(tag)) {
@@ -230,7 +230,7 @@ export class ReservedChecker {
    */
   _checkGroupRequirements(group, specialTag, fullCheck) {
     const specialRequirements = ReservedChecker.reservedMap.get(specialTag.schemaTag.name)
-    const issues = this._checkAllowedTags(group, specialTag, specialRequirements.otherAllowedNonDefTags)
+    const issues = this._checkAllowedTags(group, specialTag, specialRequirements)
     if (issues.length > 0) {
       return issues
     }
@@ -239,22 +239,30 @@ export class ReservedChecker {
   }
 
   /**
-   * Verify that the tags in the group are allowed with the special tag
+   * Verify that the tags in the group are allowed with the special tag.
    *
-   * @param {ParsedHedGroup} group - The enclosing tag group
-   * @param {ParsedHedTag} specialTag - The special tag whose tag requirements are to be checked
-   * @param { string[]} otherAllowed - The list of tags that are allowed with this tag
-   * @returns {Issue[]|[]}
+   * @param {ParsedHedGroup} group - The enclosing tag group.
+   * @param {ParsedHedTag} specialTag - The special tag whose tag requirements are to be checked.
+   * @param { Object } requirements - The requirements for this special tag.
+   * @returns {Issue[]} - Issues because
    * @private
    */
-  _checkAllowedTags(group, specialTag, otherAllowed) {
-    if (otherAllowed === null || otherAllowed === undefined) {
+  _checkAllowedTags(group, specialTag, requirements) {
+    // The allowed tag requirement isn't applicable
+    if (requirements.otherAllowedNonDefTags === null || requirements.otherAllowedNonDefTags === undefined) {
       return []
     }
+    // Check for def or def-expand tags for a special tag that does not need them.
+    if (!requirements.requiresDef && !group.requiresDefTag && group.defCount > 0) {
+      return [generateIssue('tooManyGroupTopTags', { string: group.originalTag })]
+    }
+
+    // Isolate the other top tags.
     const otherTopTags = group.topTags.filter((tag) => tag !== specialTag)
     if (otherTopTags.length === 0) {
       return []
     }
+
     const encountered = new Set()
     for (const tag of otherTopTags) {
       if (encountered.has(tag.schemaTag.name)) {
@@ -265,7 +273,7 @@ export class ReservedChecker {
         continue
       }
       // This tag is not allowed with the special tag
-      if (!otherAllowed.includes(tag.schemaTag.name)) {
+      if (!requirements.otherAllowedNonDefTags.includes(tag.schemaTag.name)) {
         return [
           generateIssue('invalidGroupTopTags', { tags: getTagListString(group.topTags), string: group.originalTag }),
         ]
@@ -285,10 +293,12 @@ export class ReservedChecker {
    * @private
    */
   _checkAllowedGroups(group, specialTag, requirements, fullCheck) {
-    // Group checks are not applicable to this special tag
+    // Group checks are not applicable to this special tag.
     if (!requirements.tagGroup) {
       return []
     }
+
+    // Proper Def and Def-expand count for a tag that requires a def is checked when group is created.
     let subgroupCount = group.topGroups.length
     if (group.hasDefExpandChildren && group.requiresDefTag !== null) {
       subgroupCount = subgroupCount - 1
diff --git a/parser/tagConverter.js b/parser/tagConverter.js
index 837a6ac4..fcbae2f1 100644
--- a/parser/tagConverter.js
+++ b/parser/tagConverter.js
@@ -137,23 +137,6 @@ export default class TagConverter {
     }
   }
 
-  /*  /!**
-   * Handle the case where it does not allow an extension or if it requires a child and doesn't have one.
-   * @param {int} tagLevelIndex index of the tag
-   * @throws {IssueError} If the tag has an extension that is not allowed.
-   *!/
-  _checkExtensionRequirements(tagLevelIndex) {
-    // Check allow extension or requires a child
-    const schemaTag = this.getSchemaTag(tagLevelIndex - 1)
-    const remainder = this.tagLevels.slice(tagLevelIndex).join('/')
-    if (this.special.noExtension.includes(schemaTag.name) && remainder !== '') {
-      IssueError.generateAndThrow('invalidExtension',{tag: remainder, parentTag: schemaTag.name})
-    }
-    if (remainder === '' && schemaTag.hasAttributeName('requireChild')) (
-      IssueError.generateAndThrow('childRequired', {tag:schemaTag.name})
-    )
-  }*/
-
   _getSchemaTag(tagLevelIndex) {
     const tagLevel = this.tagLevels[tagLevelIndex].toLowerCase()
     return this.tagMapping.getEntry(tagLevel)
diff --git a/spec_tests/javascriptTests.json b/spec_tests/javascriptTests.json
index e63f341b..0e4f0786 100644
--- a/spec_tests/javascriptTests.json
+++ b/spec_tests/javascriptTests.json
@@ -2728,7 +2728,7 @@
     "name": "sidecar-braces-circular-reference",
     "description": "The item in curly braces has a HED annotation that contains curly braces.",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -2836,7 +2836,7 @@
     "name": "sidecar-braces-self-reference",
     "description": "The item in curly braces has a HED annotation that contains itself.",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -2948,7 +2948,7 @@
     "name": "sidecar-braces-appear-as-value-rather-than-tag",
     "description": "The curly braces are in a value rather than as a separate tag substitute.",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -4186,7 +4186,7 @@
     "name": "tag-group-error-missing",
     "description": "A tag has tagGroup or topLevelTagGroup attribute, but is not enclosed in parentheses.",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -4286,7 +4286,7 @@
     "name": "tag-group-error-not-top-level",
     "description": "A tag with the topLevelTagGroup does not appear at a HED tag group at the top level in an assembled HED annotation.",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -4357,7 +4357,7 @@
     "name": "multiple-top-level-tags-in-same-group",
     "description": "Multiple tags with the topLevelTagGroup attribute appear in the same top-level tag group. (Delay and Duration are allowed to be in the same topLevelTagGroup).",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -4842,19 +4842,19 @@
     "name": "tag-requires-child-no-child",
     "description": "A tag has the requireChild schema attribute but does not have a child.",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
-        "fails": ["(Blue, Description)", "Label, Red"],
-        "passes": ["(Blue, Description/Yes this is a description., (Red))", "Label/Redish, Red"]
+        "fails": ["(Blue, Def)", "Def, Red"],
+        "passes": ["(Blue, Def/MyColor, (Red))", "Label/Redish, Def/MyColor, Red"]
       },
       "sidecar_tests": {
         "fails": [
           {
             "event_code": {
               "HED": {
-                "face": "(Blue, Description)",
+                "face": "(Blue, Def)",
                 "ball": "Label, Red"
               }
             }
@@ -4864,7 +4864,7 @@
           {
             "event_code": {
               "HED": {
-                "face": "(Blue, Description/Yes this is a description., (Red))",
+                "face": "(Blue, Def/MyColor, (Red))",
                 "ball": "Label/Redish, Red"
               }
             }
@@ -4875,14 +4875,13 @@
         "fails": [
           [
             ["onset", "duration", "HED"],
-            [4.5, 0, "(Blue, Description)"],
-            [5.0, 0, "Label, Red"]
+            [4.5, 0, "(Blue, Def)"]
           ]
         ],
         "passes": [
           [
             ["onset", "duration", "HED"],
-            [4.5, 0, "(Blue, Description/Yes this is a description., (Red))"],
+            [4.5, 0, "(Blue, Def/MyColor, (Red))"],
             [5.0, 0, "Label/Redish, Red"]
           ]
         ]
@@ -4893,7 +4892,7 @@
             "sidecar": {
               "event_code": {
                 "HED": {
-                  "face": "(Blue, Description)",
+                  "face": "(Blue, Def)",
                   "ball": "Label, Red"
                 }
               }
@@ -4931,7 +4930,7 @@
     "name": "temporal-tag-error-not-tag-group",
     "description": "An Onset or Offset tag does not appear in a tag group.",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -5011,7 +5010,7 @@
     "name": "temporal-tag-error-nested-group",
     "description": "An Onset or Offset tag appears in a nested tag group (not a top-level tag group).",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -5094,7 +5093,7 @@
     "name": "temporal-tag-error-wrong-number-of-defs",
     "description": "An Onset or Offset tag is not grouped with exactly one Def-expand tag group or a Def tag.",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -5181,7 +5180,7 @@
     "name": "temporal-tag-error-onset-has-more-groups",
     "description": "An Onset group has more than one additional tag group.",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -5271,7 +5270,7 @@
     "name": "temporal-tag-error-offset-has-groups",
     "description": "An Offset appears with one or more tags or additional tag groups.",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -5376,7 +5375,7 @@
     "name": "temporal-tag-error-offset-with-no-onset",
     "description": "An Offset tag associated with a given definition appears after a previous Offset tag without the appearance of an intervening Onset of the same name.",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -5450,7 +5449,7 @@
     "name": "temporal-tag-error-extra tags",
     "description": "An Onset tag group with has tags besides the anchor Def or Def-expand that are not in a tag group.",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -5535,7 +5534,7 @@
     "name": "temporal-tag-error-duplicated-onset-or-offset",
     "description": "An Onset or an Offset with a given Def or Def-expand anchor appears in the same event marker with another Onset or Offset that uses the same anchor.",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -5624,7 +5623,7 @@
     "name": "temporal-tag-error-inset-outside-its-event",
     "description": "An Inset tag is not grouped with a Def or Def-expand of an ongoing Onset.",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -5701,7 +5700,7 @@
     "name": "temporal-tag-error-inset-group-has-extras",
     "description": "An Inset group has tags or groups in addition to its defining Def or Def-expand.",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -5781,7 +5780,7 @@
     "name": "temporal-tag-error-duration-group",
     "description": "A Duration or Delay has extra tags or groups.",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -5845,7 +5844,7 @@
     "name": "temporal-tag-error-tag-appears-where-not-allowed",
     "description": "A temporal tag appears appears in a tsv with no onset column",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -5941,11 +5940,15 @@
     "name": "temporal-tag-error-not-tag-group-delay",
     "description": "A Delay is not in the tag group.",
     "warning": false,
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
-        "fails": ["(Delay, Red)", "(Delay, Def/Acc/5.4)"],
+        "fails": [
+          "(Delay/5, Red)",
+          "(Delay/5, Def/Acc/5.4)",
+          "(Delay/5, (Def-expand/Acc/5.4, (Acceleration/5.4 m-per-s^2, Red)))"
+        ],
         "passes": ["(Delay/5 s, (Def/Acc/5.4))"]
       },
       "sidecar_tests": {
@@ -6030,7 +6033,7 @@
     "alt_codes": ["TAG_GROUP_ERROR"],
     "name": "temporal-tag-error-nested-group-delay",
     "description": "A delay appears in a group not in the top level.",
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -6112,7 +6115,7 @@
     "alt_codes": ["TAG_GROUP_ERROR"],
     "name": "temporal-tag-error-wrong-number-of-defs-delay",
     "description": "An Onset or Offset tag is not grouped with exactly one Def-expand tag group or a Def tag.",
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -6201,7 +6204,7 @@
     "alt_codes": ["TAG_GROUP_ERROR"],
     "name": "temporal-tag-error-onset-has-more-groups-delay",
     "description": "An Onset group has more than one additional tag group.",
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -6219,7 +6222,13 @@
           {
             "event_code": {
               "HED": {
-                "face": "(Delay/5.0 s, Onset, Def/MyColor, (Red), (Blue))",
+                "face": "(Delay/5.0 s, Onset, Def/MyColor, (Red), (Blue))"
+              }
+            }
+          },
+          {
+            "event_code": {
+              "HED": {
                 "ball": "(Delay/5.0 s, (Def-expand/MyColor, (Label/Pie)), (Green), (Yellow), Onset)"
               }
             }
@@ -6240,7 +6249,10 @@
         "fails": [
           [
             ["onset", "duration", "HED"],
-            [4.5, 0, "(Delay/5.0 s, Onset, Def/MyColor, (Red), (Blue))"],
+            [4.5, 0, "(Delay/5.0 s, Onset, Def/MyColor, (Red), (Blue))"]
+          ],
+          [
+            ["onset", "duration", "HED"],
             [5.5, 0, "(Delay/5.0 s, (Def-expand/MyColor, (Label/Pie)), (Green), ((Yellow)), Onset)"]
           ]
         ],
@@ -6258,15 +6270,38 @@
             "sidecar": {
               "event_code": {
                 "HED": {
-                  "face": "(Delay/5.0 s, (Def-expand/MyColor, (Label/Pie)), (Green), ((Yellow)), Onset)",
+                  "face": "(Delay/5.0 s, (Def-expand/MyColor, (Label/Pie)), (Green), ((Yellow)), Onset)"
+                }
+              }
+            },
+            "events": [
+              ["onset", "duration", "event_code", "HED"],
+              [4.5, 0, "face", "Red, Def/MyColor"]
+            ]
+          },
+          {
+            "sidecar": {
+              "event_code": {
+                "HED": {
                   "ball": "(Delay/5.0 s, Onset, Def/MyColor, (Red), (Blue))"
                 }
               }
             },
             "events": [
               ["onset", "duration", "event_code", "HED"],
-              [4.5, 0, "face", "Red, Def/MyColor"],
-              [5.0, 0, "ball", "Green"],
+              [5.0, 0, "ball", "Green"]
+            ]
+          },
+          {
+            "sidecar": {
+              "event_code": {
+                "HED": {
+                  "ball": "(Delay/5.0 s, Onset, Def/MyColor, (Blue))"
+                }
+              }
+            },
+            "events": [
+              ["onset", "duration", "event_code", "HED"],
               [6.0, 0, "n/a", "(Delay/5.0 s, Def/MyColor, (Red), (Blue), Onset)"]
             ]
           }
@@ -6296,7 +6331,7 @@
     "alt_codes": ["TAG_GROUP_ERROR"],
     "name": "temporal-tag-error-offset-has-groups-delay",
     "description": "An Offset appears with one or more tags or additional tag groups.",
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -6310,7 +6345,15 @@
               "HED": {
                 "face": "(Delay/5.0 s, Onset, Def/MyColor)",
                 "ball": "(Delay/5.0 s, (Def-expand/MyColor, (Label/Pie)), Onset)",
-                "square": "(Delay/5.0 s, Offset, Def/MyColor, (Red))",
+                "square": "(Delay/5.0 s, Offset, Def/MyColor, (Red))"
+              }
+            }
+          },
+          {
+            "event_code": {
+              "HED": {
+                "face": "(Delay/5.0 s, Onset, Def/MyColor)",
+                "ball": "(Delay/5.0 s, (Def-expand/MyColor, (Label/Pie)), Onset)",
                 "circle": "(Delay/5.0 s, (Def-expand/MyColor, (Label/Pie)), Offset, Blue)"
               }
             }
@@ -6351,6 +6394,24 @@
       },
       "combo_tests": {
         "fails": [
+          {
+            "sidecar": {
+              "event_code": {
+                "HED": {
+                  "face": "(Delay/5.0 s, Onset, Def/MyColor)",
+                  "ball": "(Delay/5.0 s, (Def-expand/MyColor, (Label/Pie)), Onset)",
+                  "square": "(Delay/5.0 s, Offset, Def/MyColor)"
+                }
+              }
+            },
+            "events": [
+              ["onset", "duration", "event_code", "HED"],
+              [4.5, 0, "face", "n/a"],
+              [4.8, 0, "square", "n/a"],
+              [4.9, 0, "ball", "Green"],
+              [5.5, 0, "n/a", "(Delay/5.0 s, (Def-expand/MyColor, (Label/Pie)), Offset, Blue), Orange"]
+            ]
+          },
           {
             "sidecar": {
               "event_code": {
@@ -6366,8 +6427,7 @@
               ["onset", "duration", "event_code", "HED"],
               [4.5, 0, "face", "n/a"],
               [4.8, 0, "square", "n/a"],
-              [4.9, 0, "ball", "Green"],
-              [5.5, 0, "n/a", "(Delay/5.0 s, (Def-expand/MyColor, (Label/Pie)), Offset, Blue)", "Orange"]
+              [4.9, 0, "ball", "Green"]
             ]
           }
         ],
@@ -6400,7 +6460,7 @@
     "alt_codes": ["TAG_GROUP_ERROR"],
     "name": "temporal-tag-error-mismatch-delay",
     "description": "An Offset tag associated with a given definition appears after a previous Offset tag without the appearance of an intervening Onset of the same name.",
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -6473,7 +6533,7 @@
     "alt_codes": ["TAG_GROUP_ERROR"],
     "name": "temporal-tag-error-extra tags-delay",
     "description": "An Onset tag group with has tags besides the anchor Def or Def-expand that are not in a tag group.",
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -6557,7 +6617,7 @@
     "alt_codes": ["TAG_GROUP_ERROR"],
     "name": "temporal-tag-error-duplicated-onset-or-offset-delay",
     "description": "An Onset or an Offset with a given Def or Def-expand anchor appears in the same event marker with another Onset or Offset that uses the same anchor.",
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -6645,7 +6705,7 @@
     "alt_codes": ["TAG_GROUP_ERROR"],
     "name": "temporal-tag-error-inset-outside-its-event-delay",
     "description": "An Inset tag is not grouped with a Def or Def-expand of an ongoing Onset.",
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -6721,7 +6781,7 @@
     "alt_codes": ["TAG_GROUP_ERROR"],
     "name": "temporal-tag-error-inset-group-has-extras-delay",
     "description": "An Inset group has tags or groups in addition to its defining Def or Def-expand.",
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -6800,7 +6860,7 @@
     "alt_codes": ["TAG_GROUP_ERROR"],
     "name": "temporal-tag-error-tag-appears-where-not-allowed-delay",
     "description": "An Inset, Offset, or Onset tag appears in a tsv with no onset column",
-    "schema": "8.2.0",
+    "schema": "8.3.0",
     "definitions": ["(Definition/Acc/#, (Acceleration/# m-per-s^2, Red))", "(Definition/MyColor, (Label/Pie))"],
     "tests": {
       "string_tests": {
@@ -6855,7 +6915,7 @@
               "event_code": {
                 "HED": {
                   "face": "(Delay/5.0 s, Def/MyColor, Duration)",
-                  "ball": "(Delay/5.0 s, Def/MyColor, Delay)"
+                  "ball": "(Delay/5.0 s, Def/MyColor, Delay/4.2)"
                 }
               }
             },
diff --git a/tests/stringParserTests.spec.js b/tests/stringParserTests.spec.js
index fbadf4cb..f3f23b15 100644
--- a/tests/stringParserTests.spec.js
+++ b/tests/stringParserTests.spec.js
@@ -12,7 +12,7 @@ import { shouldRun, getHedString } from './testUtilities'
 
 const skipMap = new Map()
 const runAll = true
-const runMap = new Map([['tag-strings', ['multiple-complex-duplicates']]])
+const runMap = new Map([['special-tag-group-tests', ['inset-delay-def']]])
 
 describe('Null schema objects should cause parsing to bail', () => {
   it('Should not proceed if no schema and valid string', () => {
diff --git a/tests/testData/stringParserTests.data.js b/tests/testData/stringParserTests.data.js
index f5264461..48e8bda4 100644
--- a/tests/testData/stringParserTests.data.js
+++ b/tests/testData/stringParserTests.data.js
@@ -852,6 +852,19 @@ export const parseTestData = [
         errors: [],
         warnings: [],
       },
+      {
+        testname: 'delay-with-unnested-def-expand-full-check',
+        explanation: '"(Delay/5, (Def-expand/MyColor, (Label/Pie)))" needs an extra group for Def-expand.',
+        schemaVersion: '8.3.0',
+        stringIn: '(Delay/5, (Def-expand/MyColor, (Label/Pie)))',
+        stringLong: null,
+        stringShort: null,
+        fullCheck: true,
+        placeholdersAllowed: false,
+        definitionsAllowed: false,
+        errors: [generateIssue('tooManyGroupTopTags', { string: '(Delay/5, (Def-expand/MyColor, (Label/Pie)))' })],
+        warnings: [],
+      },
       {
         testname: 'offset-in-group-with-other-tags',
         explanation: '"(Offset, Item)" has an extra tag and needs a def tag.',