What Is Election Markup Language (EML)?

Election Markup Language (EML) is an open, XML-based standard designed to structure and secure the exchange of election data throughout the entire democratic process. Developed by the Organization for the Advancement of Structured Information Standards (OASIS), EML establishes a consistent data format for everything from voter registration and candidate nomination to ballot creation, vote casting, and result tabulation. This article explains what EML is, why it was developed, and how its XML-driven architecture organizes election workflows.

Understanding Election Markup Language

EML was created to solve interoperability challenges in electronic voting and election administration. Before standardized markup languages, election software vendors and administrative jurisdictions used proprietary formats. This made it difficult for different systems—such as voter databases, voting machines, tally servers, and public reporting portals—to communicate seamlessly or undergo independent audits.

By providing a vendor-neutral standard, EML ensures that data can move securely and transparently across hardware, software, and administrative boundaries while preserving data integrity.

How EML Structures Voting Data in XML

EML relies on XML Schemas (XSD) to define strictly typed, modular data structures. Every phase of an election cycle is mapped to a specific schema definition, ensuring validation, structure, and consistency.

1. Modular Message Definitions

EML organizes election processes into numerical message sequences, commonly known as schemas. Key message types include:

• EML 100 Series (Voter Registration): Handles voter registration information, voter lists (EML 110), and electoral rolls.
• EML 200 Series (Nominations and Candidacy): Manages candidate and party nominations, contest qualifications, and official candidate lists.
• EML 400 Series (Voting and Ballots): Defines ballot configurations (EML 410), voter authentication tokens (EML 420), and cast vote records (EML 440).
• EML 500 Series (Results and Tabulation): Governs result counting (EML 510) and the transmission of election outcomes to media and election authorities.
• EML 600 Series (Audit): Provides structured logs for election auditing and process verification.

2. Hierarchical Data Elements

Like standard XML, EML structures information hierarchically. An EML data instance typically contains:

• Header Information: Metadata such as transaction identifiers, timestamps, issuing authorities, and schema versions.
• Context and Event Identifiers: Unique identifiers for the election, the jurisdiction, and the specific voting channel (e.g., in-person, absentee, online).
• Contest and Option Nodes: Nested structures representing specific races (e.g., Presidential, Mayoral), list of candidates, referendums, and allowed vote limits.
• Vote and Result Nodes: Securely formatted tallies or encrypted individual ballot choices paired with contest identifiers.

3. XML Schema Validation

Because election data requires zero tolerance for error, EML schemas use XML Schema Definition (XSD) files to enforce strict validation rules. These rules dictate:

• Mandatory fields (e.g., contest IDs, timestamps).
• Data types (e.g., integers for vote counts, strings for candidate names, standardized ISO codes for dates and regions).
• Constraints on values, such as ensuring vote selections do not exceed allowed thresholds.

4. Built-in Cryptography and Security

EML is designed with security standards natively supported by XML:

• XML Signature (XML-DSig): Allows election authorities to digitally sign data payloads, ensuring that ballot definitions or results have not been altered in transit.
• XML Encryption (XML-Enc): Encrypts sensitive components—such as individual voter identities or cast ballots—to preserve voter secrecy while allowing unencrypted structural metadata to pass through verification checkpoints.

Benefits of EML in Modern Elections

• Interoperability: Connects disparate voting hardware, tabulation engines, and reporting platforms without custom translation middleware.
• Auditability and Verification: The standardized, human-readable yet machine-parseable format allows independent third parties to audit raw election data efficiently.
• Vendor Independence: Electoral commissions can purchase components from different software and hardware providers without fear of proprietary lock-in.
• Process Integrity: Strict schema validation and cryptographic wrappers prevent malformed data and detect tampering.