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Prompt Markup Language

The home of XML Schemas for PML (Prompt Markup Language), PML Workflow and related Java Types

PML, Prompt Markup Language

Motivation

PML was created to design good User Prompts & System Prompts to mitigate ambiguity in frontier model's execution.

PML is an XML Schema that helps software engineers model User Prompts & System Prompts effectively. Once the prompt is modeled in XML, it can be converted into Markdown, a format that models understand well. Using the PML Schema guidelines, it is easier to ensure that nothing important is missed when defining a prompt designed for production environments.

Why XML format?

Java software engineers use XML daily because Maven is based on XML and it has a schema, so it is a familiar format for everyone.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>info.jab.pml</groupId>
    <artifactId>prompt-markup-language</artifactId>
    <version>0.3.0</version>
    <packaging>pom</packaging>

    <name>prompt-markup-language</name>

    <properties>
        <java.version>25</java.version>
        <maven.version>3.9.10</maven.version>
    </properties>

    ...
</project>

The XML format has several features that are pretty interesting for this project:

  • Syntax validation with an XML Schema
  • The capacity to transform to another format like Markdown
  • The capacity to compose documents from other sources
  • The capacity to mix heterogeneous sources from different technologies like bash scripts, other documents, examples written in Java inside XML comments
  • Good support in Java
  • Good tooling support in in JVM ecosystem

With these premises in mind, PML was designed.

Examples

Hello World in console:

You could define the following prompt:

<?xml version="1.0" encoding="UTF-8"?>
<prompt>
    <goal>
        Print "Hello World" in the console
    </goal>
</prompt>

But with this anemic prompt, exist a high probability that frontier models could not implement in the same way that you have in mind. Lets iterate this idea to show how to use PML.

A PML Schema defines the following parts:

<!-- Root element for a prompt -->
<xs:element name="prompt">
    <xs:complexType>
        <xs:sequence>
            <xs:element ref="metadata" minOccurs="0"/>
            <xs:element ref="title" minOccurs="0"/>
            <xs:element ref="role" minOccurs="0"/>
            <xs:element ref="tone" minOccurs="0"/>
            <xs:element ref="context" minOccurs="0"/>
            <xs:element ref="goal"/>
            <xs:element ref="constraints" minOccurs="0"/>
            <xs:element ref="steps" minOccurs="0" />
            <xs:element ref="examples" minOccurs="0"/>
            <xs:element ref="output-format" minOccurs="0"/>
            <xs:element ref="safeguards" minOccurs="0"/>
            <xs:element ref="acceptance-criteria" minOccurs="0"/>
        </xs:sequence>
    </xs:complexType>
</xs:element>

Some parts are mandatory and others not. Lets continue with the next example implementing the same idea in Java.

Hello World in Java:

<?xml version="1.0" encoding="UTF-8"?>
<prompt xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="https://jabrena.github.io/pml/schemas/0.3.0/pml.xsd">
    <title>Develop a HelloWorld Java Class program</title>

    <role>You are a Senior software engineer with extensive experience in Java software development</role>

    <goal>Develop a classic Java class HelloWorld.java program that print "Hello World" in the console only</goal>

    <constraints>
        <constraint-list>
            <constraint>The develop the class in the Maven module `sandbox`</constraint>
            <constraint>The develop the class in the package info.jab.examples</constraint>
            <constraint>Don't invest time in planning</constraint>
            <constraint>Don't create any test class</constraint>
            <constraint>Don't touch the build file (pom.xml)</constraint>
        </constraint-list>
    </constraints>

    <output-format>
        <output-format-list>
            <output-format-item>Don't explain anything</output-format-item>
        </output-format-list>
    </output-format>

    <safeguards>
        <safeguards-list>
            <safeguards-item>Build the solution with Maven Only</safeguards-item>
        </safeguards-list>
    </safeguards>

    <acceptance-criteria>
        <acceptance-criteria-list>
            <acceptance-criteria-item>The solution is compiled successfully with `./mvnw clean compile -pl sandbox`</acceptance-criteria-item>
            <acceptance-criteria-item>The solution only prints "Hello World" in the console</acceptance-criteria-item>
            <acceptance-criteria-item>The solution is committed and pushed to the branch to create the PR</acceptance-criteria-item>
            <acceptance-criteria-item>Only commit java sources only and push the changes to the branch to create the PR</acceptance-criteria-item>
        </acceptance-criteria-list>
    </acceptance-criteria>
</prompt>

Java 25 Installation:

In your prompts, you could have to include scripts like in this prompt:

<?xml version="1.0" encoding="UTF-8"?>
<prompt xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:noNamespaceSchemaLocation="https://jabrena.github.io/pml/schemas/0.3.0/pml.xsd">
    <title>Install Java 25 in Cursor Cloud Agent</title>

    <role>System Administrator with expertise in Java development environments and package management for Linux systems</role>

    <goal>Update the VM to Java 25. Follow the next step to achieve the goal.</goal>

    <steps>
        <step number="1">
            <step-title>Install Java 25 with SDKMAN</step-title>
            <step-content>
                ```bash
                sudo apt update
                # Install SDKMAN
                curl -s "https://get.sdkman.io" | bash
                source "$HOME/.sdkman/bin/sdkman-init.sh"
                sdk install java 25.0.1-graalce
                sdk default java 25.0.1-graalce
                java -version
                ```
            </step-content>
            <step-constraints>
                <step-constraint-list>
                    <step-constraint>Do not invest time in planning</step-constraint>
                    <step-constraint>Only install the component with the given command</step-constraint>
                </step-constraint-list>
            </step-constraints>
        </step>
    </steps>

    <output-format>Do not explain anything</output-format>

    <safeguards>Verify that java is configured for java 25 executing `java -version`</safeguards>

    <acceptance-criteria>
        <acceptance-criteria-list>
            <acceptance-criteria-item>The java version is 25</acceptance-criteria-item>
            <acceptance-criteria-item>The java installation is successful</acceptance-criteria-item>
        </acceptance-criteria-list>
    </acceptance-criteria>
</prompt>

PML Workflows

Motivation

Using Frontier models, you could delegate coding tasks, and the final outcome of a task could be produced by executing a set of prompts.

A PML Workflow file define the way of a set prompts will be executed by an Engine

Prompts formats

Prompts can be defined in 3 different ways:

  • PML (*.pml)
  • Markdown (*.md)
  • Plain text (.txt)

Agentic patterns

Sequence pattern

<?xml version="1.0" encoding="UTF-8"?>
<pml-workflow>
    <sequence model="default" repository="https://github.com/jabrena/wjax25-demos">
        <prompt src="prompt1.xml" />
        <prompt src="prompt2.md" />
        <prompt src="prompt3.txt" />
    </sequence>
</pml-workflow>

Parallel pattern

<?xml version="1.0" encoding="UTF-8"?>
<pml-workflow xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
              xsi:noNamespaceSchemaLocation="https://jabrena.github.io/pml/schemas/0.3.0-SNAPSHOT/pml-workflow.xsd">
    <parallel src="prompt-toc.xml" bindResultType="List_Integer">
        <sequence model="default" repository="https://github.com/jabrena/wjax25-demos">
            <prompt src="prompt2.xml" bindResultExp="$get()"/>
        </sequence>
    </parallel>
</pml-workflow>

PML to Mardown CLI

The repository provides a CLI tool to convert PML files into Markdown in an easy way.

./mvnw clean package
java -jar cli/target/pml-to-md-0.4.0-SNAPSHOT.jar --help
java -jar cli/target/pml-to-md-0.4.0-SNAPSHOT.jar validate cli/src/test/resources/pml/pml-hello-world.xml
java -jar cli/target/pml-to-md-0.4.0-SNAPSHOT.jar convert cli/src/test/resources/pml/pml-hello-world-template.xml --template MESSAGE "Hello World"
java -jar cli/target/pml-to-md-0.4.0-SNAPSHOT.jar convert cli/src/test/resources/pml/pml-hello-world-template-multiple.xml --template MESSAGE "Hello World" CHANNEL "Console"

Java Bindings

import info.jab.pml.model.*;

Prompt prompt = PromptBuilder.create()
    .withRole("""
        You are a Senior software engineer
        with extensive experience in Java software development
        """)
    .withGoal("Help the Java developer ecosystem to make life easier")
    .build();

Changelog

References

Cursor rules ecosystem

Powered by Cursor with ❤️ from Madrid

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The home of XML Schemas for PML (Prompt Markup Language), PML Workflow and related Java Types

jabrena.github.io/pml/schemas/

Topics

system-prompts

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v0.4.0-SNAPSHOT Latest
Dec 12, 2025

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