Automated Bibliography Checker

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Overview

This guide explains the various errors, warnings, and suggestions that the BibTeX validator produces, their relevance in modern LaTeX workflows, and how the validator adapts to different bibliography processors.

Important Context: BibTeX vs Biber

The validator now automatically detects whether you are using traditional BibTeX or modern Biber/BibLaTeX based on:

• Entry types used (e.g., @online, @software indicate Biber)
• Field names used (e.g., journaltitle, urldate indicate BibLaTeX)
• UTF-8 content (suggests modern Biber setup)

This distinction affects how errors are reported because:

• Biber handles UTF-8 natively and has different field requirements
• Traditional BibTeX requires ASCII and specific field names
• Many "errors" in BibTeX are perfectly valid in Biber/BibLaTeX

You can also manually specify the processor in the validation options.

Validation Levels

The validator offers three levels:

• Strict: Enforces ASCII-only, rigid formatting rules, title capitalization checks
• Standard: Default balanced approach (recommended for most users)
• Permissive: Minimal checking, suitable for Biber/BibLaTeX users

Error Categories and Analysis

1. Character Encoding Errors

NON_ASCII_CHARACTER

What it means: Non-ASCII characters (accented letters, special symbols) found in the bibliography.

Relevance:

• Traditional BibTeX: Error in strict mode, warning in standard mode
• Biber/BibLaTeX: Automatically ignored - UTF-8 is fully supported
• Modern pdfLaTeX with inputenc: Often fine with \usepackage[utf8]{inputenc}

How to fix:

• Replace é with \'{e}, ñ with \~{n}, etc.
• Or switch to Biber and use UTF-8 freely

Validator behavior: Now auto-detects Biber usage and suppresses UTF-8 warnings accordingly.

PROBLEMATIC_QUOTES

What it means: Curly/smart quotes ("") instead of straight quotes ("").

Relevance: Always relevant - these will render incorrectly in LaTeX.

How to fix: Replace with straight quotes or LaTeX commands (`` and '').

Validator critique: Good catch - this is a common copy-paste error.

2. Entry Structure Errors

EMPTY_ENTRY_KEY / MALFORMED_ENTRY_KEY

What it means: Missing or invalid citation keys (e.g., @article{, or @article{my key with spaces,).

Relevance: Critical - will cause compilation failure.

How to fix: Provide valid keys using only letters, numbers, hyphens, colons, and underscores.

Validator critique: The regex-based validation might fail on complex edge cases. The error handling for malformed keys is good.

NUMERIC_ENTRY_KEY

What it means: Citation key contains only numbers (e.g., @article{12345,).

Relevance:

• Works technically but poor practice
• Can conflict with numeric citation styles

How to fix: Add descriptive text (e.g., smith2023 instead of 2023).

Validator critique: Good to warn about this, but making it configurable is appropriate.

DUPLICATE_ENTRY_KEY

What it means: Same citation key used multiple times.

Relevance: Critical - only the first entry will be used.

How to fix: Make each key unique.

Validator critique: Essential check, well implemented.

3. Field and Syntax Errors

MISSING_COMMA

What it means: Missing comma between fields.

Relevance: Critical - causes parsing errors.

How to fix: Add commas after each field except the last one.

UNBALANCED_BRACE / UNCLOSED_BRACE

What it means: Mismatched { and } braces.

Relevance: Critical - will break parsing entirely.

How to fix: Ensure every { has a matching }.

MISSING_REQUIRED_FIELD

What it means: Entry type missing standard required fields.

Relevance:

• Traditional BibTeX: Warning - may result in incomplete citations
• Biber/BibLaTeX: Less critical - more flexible field requirements

How to fix: Add the missing fields or verify your bibliography style does not require them.

Validator behavior: Now detects BibTeX vs BibLaTeX field conventions:

• Recognizes date vs year differences
• Understands journaltitle vs journal variations
• Provides appropriate suggestions based on detected processor

UNENCLOSED_FIELD_VALUE (Now a Warning)

What it means: Field values not in braces or quotes.

Relevance:

• Numbers can be unbraced
• Single words often work unbraced
• Multi-word values should be enclosed

How to fix: Enclose in {...} or "..." for safety.

Validator behavior: Changed from error to warning - many unbraced values are valid.

4. URL-Related Errors

UNESCAPED_AMPERSAND

What it means: URLs contain & instead of \&.

Relevance:

• With \usepackage{url} or hyperref: Automatically handled - shown as suggestion only
• Without URL packages: Warning - may need escaping

How to fix:

• Best: Use \url{...} command in the document
• Alternative: Escape as \&

Validator behavior: Now detects likely package usage and adjusts severity accordingly.

UNESCAPED_HASH / UNESCAPED_PERCENT

What it means: URLs contain # or % characters.

Relevance: Similar to ampersand - depends on packages used.

Validator behavior: Warnings only when URL packages likely not loaded.

MISSING_PROTOCOL

What it means: URL lacks http:// or https://.

Relevance: Low - more about consistency than functionality.

5. Consistency Suggestions

INCONSISTENT_YEAR_FORMAT

What it means: Mixing 2-digit and 4-digit years.

Relevance: Aesthetic issue only.

MIXED_URL_FORMATS

What it means: Using both shortened and full URLs.

Relevance: Aesthetic/consistency issue.

6. New Validation Checks

INVALID_MONTH / FULL_MONTH_NAME

What it means: Month field contains invalid values or full month names instead of abbreviations.

Relevance:

• BibTeX expects three-letter abbreviations (jan, feb, mar, etc.)
• Full month names may not format correctly in some styles

How to fix: Use three-letter abbreviations without braces: month = jan

CORPORATE_AUTHOR_BRACING

What it means: Corporate/institutional authors not properly protected from splitting.

Relevance: BibTeX treats "and" as an author separator, which breaks corporate names.

Example problem: author = {Microsoft Corporation and Google Inc.} becomes two authors.

How to fix: Use double braces: author = {{Microsoft Corporation}}

MISSING_DOI_URL

What it means: Recent publications (last 5 years) without DOI or URL.

Relevance: Suggestion only - modern publications typically have DOIs for accessibility.

How to fix: Add doi = {10.xxxx/yyyy} or url = {https://...}

INCONSISTENT_CAPITALIZATION / UNPROTECTED_ACRONYM

What it means: Title field has inconsistent capitalization or unprotected acronyms.

Relevance:

• Some bibliography styles force lowercase, breaking acronyms
• Only checked in strict mode

How to fix:

• Use sentence case for titles
• Protect acronyms: title = {Study of {DNA} Sequences}

Improvements in This Version

1. Automatic BibTeX vs Biber Detection

The validator now automatically detects which processor you are likely using and adjusts its checks accordingly.

2. Enhanced Entry Type Support

Now recognizes modern entry types:

• @software, @dataset, @online (fully supported)
• Various BibLaTeX-specific types
• Appropriate required fields for each processor

3. Additional Validation Checks

New checks for common issues:

• Invalid month formats
• Corporate author formatting
• Missing DOI/URL for recent publications
• Title capitalization consistency
• Field name variations (date/year, journal/journaltitle)

4. Context-Aware Validation

• Package awareness for URL escaping
• Processor-specific field requirements
• Smarter error vs warning classification

5. More Helpful Messages

• Errors that are actually warnings are now properly classified
• Suggestions provided for processor-specific alternatives
• Clear indication of which processor was detected

Recommendations for Users

1. Let the validator auto-detect your setup:
   • It will identify BibTeX vs Biber usage
   • Errors will be adjusted accordingly
   • Check the "detectedProcessor" in results
2. Critical errors to always fix:
   • Unbalanced braces
   • Empty entry keys
   • Duplicate keys
   • Missing commas
   • Problematic quotes (curly quotes)
3. Warnings to evaluate based on your setup:
   • Character encoding (ignored if Biber detected)
   • URL escaping (depends on packages)
   • Required fields (depends on bibliography style)
   • Unenclosed field values (often safe to ignore)
4. Suggestions are optional improvements:
   • Missing DOI/URL for recent work
   • Corporate author formatting
   • LaTeX escape sequences
   • Consistency in formatting

Best Practices

1. Use Biber/BibLaTeX for new projects - more flexible and powerful
2. Be consistent even when not required - aids maintenance
3. Test with your actual document - validators cannot know your full setup
4. Use reference managers that export clean BibTeX/BibLaTeX
5. Protect special content - acronyms in titles, corporate authors

Validator Settings Recommendations

• For modern Biber/BibLaTeX users: Use standard or permissive mode
• For traditional BibTeX with English content: Use standard mode
• For traditional BibTeX with strict requirements: Use strict mode
• For maximum compatibility: Use strict mode and fix all issues
• If unsure: Use standard mode and let auto-detection help

Understanding Validation Results

The validator now provides:

• Detected Processor: Shows whether BibTeX or Biber was detected
• Errors: Must fix for compilation to work
• Warnings: Should fix for better compatibility
• Suggestions: Optional improvements for best practices

Remember: The validator adapts to your detected setup. A warning for BibTeX users might be ignored for Biber users automatically.

Available Validation Options

You can customize the validator behavior with these options:

Processor Settings

• processor: 'auto', 'bibtex', or 'biber' (default: 'auto')
• urlPackageLoaded: true/false/'auto' - whether URL package is loaded
• hyperrefLoaded: true/false/'auto' - whether hyperref is loaded

Character Encoding

• requireAsciiOnly: Enforce ASCII-only characters
• warnOnNonAscii: Warn about UTF-8 characters
• suggestLatexEscapes: Suggest LaTeX escapes for special characters

Structure Validation

• enforceRequiredFields: Check for required fields by entry type
• strictEntryKeys: Disallow special characters in citation keys
• allowNumericKeys: Allow number-only citation keys

Syntax Checking

• requireBraceEnclosure: Require all field values to be enclosed
• strictCommaPlacement: Enforce proper comma usage
• checkUrlEscaping: Check for unescaped URL characters

Additional Checks

• checkDuplicateKeys: Find duplicate citation keys
• checkYearConsistency: Check for consistent year formatting
• checkUrlConsistency: Check for mixed URL formats
• checkMonthFormat: Validate month field values
• checkCorporateAuthors: Detect improperly formatted corporate authors
• checkRecentPublications: Suggest DOI/URL for recent publications
• checkTitleCapitalization: Check title capitalization consistency

Validation Levels

• validationLevel: 'strict', 'standard', or 'permissive'

Each level sets appropriate defaults for the above options.

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