diff --git a/projects/logging/logging-model/src/main/kotlin/io/tnboot/logging/model/Error.kt b/projects/logging/logging-model/src/main/kotlin/io/tnboot/logging/model/Error.kt
new file mode 100644
index 0000000..34d1e43
--- /dev/null
+++ b/projects/logging/logging-model/src/main/kotlin/io/tnboot/logging/model/Error.kt
@@ -0,0 +1,18 @@
+package io.tnboot.logging.model
+
+/**
+ * Represents an error.
+ */
+interface Error {
+	val className: String
+	val message: String?
+	val stack: Array<StackTraceElement>
+	val commonFrames: Int
+	val cause: Error?
+	val cyclic: Boolean
+
+	/**
+	 * Returns a string representation of this error.
+	 */
+	val repr: String
+}
diff --git a/projects/logging/logging-model/src/main/kotlin/io/tnboot/logging/model/LogLevel.kt b/projects/logging/logging-model/src/main/kotlin/io/tnboot/logging/model/LogLevel.kt
new file mode 100644
index 0000000..d1dd853
--- /dev/null
+++ b/projects/logging/logging-model/src/main/kotlin/io/tnboot/logging/model/LogLevel.kt
@@ -0,0 +1,24 @@
+package io.tnboot.logging.model
+
+/**
+ * Log level enum, from the most verbose to the least verbose.
+ *
+ * This class exists purely as a translation layer between
+ * configuration and Slf4J and Logback.
+ */
+enum class LogLevel {
+	Trace,
+	Debug,
+	Info,
+	Warn,
+	Error,
+	;
+
+	override fun toString(): String = when (this) {
+		Trace -> "TRACE"
+		Debug -> "DEBUG"
+		Info -> "INFO"
+		Warn -> "WARN"
+		Error -> "ERROR"
+	}
+}
diff --git a/projects/logging/logging-model/src/main/kotlin/io/tnboot/logging/model/LogPayload.kt b/projects/logging/logging-model/src/main/kotlin/io/tnboot/logging/model/LogPayload.kt
new file mode 100644
index 0000000..56a119a
--- /dev/null
+++ b/projects/logging/logging-model/src/main/kotlin/io/tnboot/logging/model/LogPayload.kt
@@ -0,0 +1,22 @@
+package io.tnboot.logging.model
+
+import java.time.Instant
+
+/**
+ * [LogPayload] is a data class that represents the payload of a log
+ * event. This is the data that is passed to Telenor Boot Logging
+ * themes when a log event is created.
+ */
+interface LogPayload {
+	val at: Instant
+	val level: LogLevel
+	val sequence: Long
+	val loggerName: String
+	val caller: Array<StackTraceElement>?
+	val thread: String?
+	val mdc: Map<String, String?>
+	val formattedMessage: String
+	val message: String
+	val arguments: Array<Any?>
+	val error: Error?
+}
diff --git a/projects/logging/logging-model/src/main/kotlin/io/tnboot/logging/model/StackTraceElement.kt b/projects/logging/logging-model/src/main/kotlin/io/tnboot/logging/model/StackTraceElement.kt
new file mode 100644
index 0000000..02ef09d
--- /dev/null
+++ b/projects/logging/logging-model/src/main/kotlin/io/tnboot/logging/model/StackTraceElement.kt
@@ -0,0 +1,22 @@
+package io.tnboot.logging.model
+
+/**
+ * Represents a single element in a stack trace.
+ */
+interface StackTraceElement {
+	val classLoaderName: String?
+	val clazz: String
+	val method: String
+	val native: Boolean
+	val module: String?
+	val version: String?
+	val file: String?
+	val line: Int?
+	val omitted: Boolean
+	val alreadyShown: Boolean
+
+	/**
+	 * Returns a string representation of this stack trace element.
+	 */
+	val repr: String
+}
diff --git a/projects/logging/logging-model/src/main/kotlin/io/tnboot/logging/model/Theme.kt b/projects/logging/logging-model/src/main/kotlin/io/tnboot/logging/model/Theme.kt
new file mode 100644
index 0000000..9cfbf55
--- /dev/null
+++ b/projects/logging/logging-model/src/main/kotlin/io/tnboot/logging/model/Theme.kt
@@ -0,0 +1,28 @@
+package io.tnboot.logging.model
+
+/**
+ * [Theme] is an interface that represents a theme for Telenor Boot
+ * Logging. A theme is responsible for rendering a log event into a
+ * string that can be written to a log file or console.
+ */
+interface Theme {
+	/**
+	 * The name of the theme.
+	 *
+	 * When implementing your theme, you should return a unique name,
+	 * as this is used to identify the theme in the configuration. This
+	 * name should be a simple string, and should not contain any
+	 * special characters. For example:
+	 *
+	 * ```
+	 * my-super-duper-cool-theme
+	 * ```
+	 *
+	 * While no validation is done on the name, except a uniqueness
+	 * check, it is recommended to follow the above guidelines.
+	 */
+	fun name(): String
+
+	/** Render a log event into a string. */
+	fun render(payload: LogPayload): String
+}
diff --git a/settings.gradle.kts b/settings.gradle.kts
index c60ef13..833c9e8 100644
--- a/settings.gradle.kts
+++ b/settings.gradle.kts
@@ -7,4 +7,5 @@ include(
 
 include(
 	":projects:logging:colorful",
+	":projects:logging:logging-model",
 )