XML Schema (XSD) Explained: Types, Validation, and Examples

What Is an XML Schema?

An XML Schema Definition (XSD) is a contract that describes which elements and attributes are allowed, in what order, and with which data types. If a document violates the schema, validators reject it—even when the XML is well-formed.

Partners publish XSDs so every supplier sends the same shape. Treat the XSD as source of truth for imports and exports.

Core Building Blocks

You only need a handful of constructs to read most partner schemas.

A Minimal XSD Example

This schema describes a list of orders with a required email and a decimal amount.

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           elementFormDefault="qualified">
  <xs:element name="records">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="record" maxOccurs="unbounded">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="order_id" type="xs:string"/>
              <xs:element name="email" type="xs:string"/>
              <xs:element name="amount" type="xs:decimal"/>
            </xs:sequence>
          </xs:complexType>
        </xs:element>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>

Common Simple Types

Built-in types cover most tabular fields you would export from CSV.

• xs:string — text, IDs, emails (often with a pattern facet).
• xs:decimal / xs:integer — amounts and counts.
• xs:boolean — true/false (not "yes"/"no" unless restricted).
• xs:date / xs:dateTime — ISO-style dates.
• xs:token — string with normalized whitespace.

How to Validate Against an XSD

Validation belongs in CI and in the upload checklist.

xmllint --noout --schema orders.xsd orders.xml

XSD and CSV Workflows

When XML is generated from a spreadsheet, map CSV columns to schema elements one-to-one. Rename headers to match element names, cast dates to xs:date shapes, and keep amounts as plain decimals without currency symbols.

Convert CSV Online’s CSV to XML Converter is useful for a first draft; then validate with the partner XSD before SFTP.

Namespaces in Schemas

Many XSDs declare a targetNamespace. Instance documents must use that namespace on the root (default or prefixed). A valid local structure with the wrong namespace still fails validation.

Real-World Examples

Where XSDs decide whether a feed is accepted.

Common Mistakes

Schema misunderstandings cause "mystery" rejections.

• Ignoring targetNamespace.
• Sending "Yes"/"No" where xs:boolean is required.
• Putting currency symbols in xs:decimal fields.
• Reordering children under xs:sequence.
• Treating well-formedness as schema validity.

Best Practices

Treat the XSD like an API contract.

• Version schemas and document breaking changes.
• Keep sample XML next to the XSD in Git.
• Validate every generated file in CI.
• Prefer regenerating from CSV over hand-editing XML.
• Flatten with XML to CSV when humans need to fix values.

Why Use Convert CSV Online?

Convert CSV Online is free, browser-based, and requires no account for everyday conversions. Build candidate XML from CSV, then validate locally with xmllint against the partner XSD. Client-side workflows work on Windows, macOS, and Linux browsers.

Conclusion

XSD turns XML from "looks okay" into a testable contract. Learn elements, types, and cardinality, validate early, and keep spreadsheet sources aligned with the schema.