XML vs TONL: Data Format Comparison for AI Applications

While XML offers mature tooling like XPath and XSD, TONL provides a modern alternative with built-in query APIs, streaming support, and advanced optimization. For LLM applications requiring both efficiency and powerful data manipulation, TONL delivers enterprise-grade capabilities with up to 69% token savings.

The Contenders

Query Capabilities Comparison

Both formats offer query capabilities, but with different approaches and complexity levels.

XML with XPath:

// Select all user names
//user/name/text()

// Filter by role
//user[role='admin']/name

// Complex nested query
//orders/order[total > 100]/items/item[quantity > 5]

TONL Query API:

// Select all user names
doc.query('users[*].name');

// Filter by role
doc.query('users[?(@.role == "admin")].name');

// Aggregation (not available in XPath)
doc.sum('orders[*].total');
doc.avg('orders[*].items[*].quantity');
doc.groupBy('users[*]', 'role');

// Fuzzy matching (unique to TONL)
import { fuzzySearch } from 'tonl/query';
fuzzySearch('Jon', ['John', 'Jane', 'Bob']);

Syntax Comparison

XML Example (267 bytes, ~160 tokens):

<?xml version="1.0" encoding="UTF-8"?>
<users>
  <user>
    <id>1</id>
    <name>Alice</name>
    <role>admin</role>
  </user>
  <user>
    <id>2</id>
    <name>Bob</name>
    <role>user</role>
  </user>
</users>

TONL Example (105 bytes, ~49 tokens - 69% reduction):

#version 1.0
users[2]{id:u32,name:str,role:str}:
  1, Alice, admin
  2, Bob, user

Advanced Features

Schema Validation

<xs:schema>
  <xs:element name="user">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="id"
          type="xs:integer"/>
        <xs:element name="name">
          <xs:simpleType>
            <xs:restriction
              base="xs:string">
              <xs:minLength
                value="3"/>
              <xs:maxLength
                value="20"/>
            </xs:restriction>
          </xs:simpleType>
        </xs:element>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>

@schema v1
@strict true

User: obj
  id: u32 required
  name: str required
    min:3 max:20
  email: str required
    pattern:email
  roles: list<str>
    required min:1

Optimization Strategies

TONL includes built-in optimization that XML lacks:

Streaming Comparison

Both formats support streaming, but with different approaches:

• XML (SAX/StAX): Event-based parsing, complex callback handling, no built-in query during stream.
• TONL: Native streaming with query support, handles multi-GB files with minimal memory, automatic chunking.

Performance Benchmarks

When to Use Which?

Stick with XML if:

• You need XSLT transformations or complex XPath queries.
• Enterprise systems mandate XML (SOAP, HL7, etc.).
• You require XML-specific features (attributes, namespaces).
• Regulatory compliance requires XML format.

Switch to TONL if:

• You need both token efficiency AND query capabilities.
• You're building LLM-powered data pipelines.
• You work with large datasets requiring streaming.
• You want built-in optimization without external tools.
• Schema validation with simpler syntax appeals to you.

Final Verdict

XML remains the standard for enterprise integrations and systems requiring XSLT transformations. However, for modern LLM applications, TONL provides a compelling alternative with native query APIs, streaming support, and advanced optimization—all while delivering 70% token savings.

For simpler use cases focused purely on token efficiency, see our XML vs TOON comparison. Learn more about TONL features or explore API cost optimization strategies.