diff --git a/app/src/main/java/com/github/braillesystems/learnbraille/data/dsl/DataStorage.kt b/app/src/main/java/com/github/braillesystems/learnbraille/data/dsl/DataStorage.kt
index e858c3c8..23f71f28 100644
--- a/app/src/main/java/com/github/braillesystems/learnbraille/data/dsl/DataStorage.kt
+++ b/app/src/main/java/com/github/braillesystems/learnbraille/data/dsl/DataStorage.kt
@@ -177,9 +177,9 @@ private fun Step.interpolateText(courseName: CourseName): Step =
         if (data !is BaseInfo) data
         else {
             when (data) {
-                is FirstInfo -> FirstInfo(interpolateTextHelper(data.xmlBody, courseName))
-                is LastInfo -> LastInfo(interpolateTextHelper(data.xmlBody, courseName))
-                is Info -> Info(interpolateTextHelper(data.xmlBody, courseName))
+                is FirstInfo -> FirstInfo(interpolateTextHelper(data.text, courseName))
+                is LastInfo -> LastInfo(interpolateTextHelper(data.text, courseName))
+                is Info -> Info(interpolateTextHelper(data.text, courseName))
             }
         }
     )
diff --git a/app/src/main/java/com/github/braillesystems/learnbraille/data/entities/BrailleDots.kt b/app/src/main/java/com/github/braillesystems/learnbraille/data/entities/BrailleDots.kt
index baa7258f..e62f0bd0 100644
--- a/app/src/main/java/com/github/braillesystems/learnbraille/data/entities/BrailleDots.kt
+++ b/app/src/main/java/com/github/braillesystems/learnbraille/data/entities/BrailleDots.kt
@@ -51,14 +51,6 @@ data class BrailleDots(
     )
 
     override fun toString() = "$b1$b2$b3$b4$b5$b6"
-
-    fun toXml(): String {
-        val dotsSymbols = this.toString().replace("F", "T").replace("E", "F")
-        var result = ""
-        dotsSymbols.dropLast(1).forEach { result += "$it, " }
-        result += dotsSymbols.takeLast(1)
-        return "($result)"
-    }
 }
 
 val BrailleDots.list: List<BrailleDot>
diff --git a/app/src/main/java/com/github/braillesystems/learnbraille/data/entities/Materials.kt b/app/src/main/java/com/github/braillesystems/learnbraille/data/entities/Materials.kt
index 98125b8e..34482385 100644
--- a/app/src/main/java/com/github/braillesystems/learnbraille/data/entities/Materials.kt
+++ b/app/src/main/java/com/github/braillesystems/learnbraille/data/entities/Materials.kt
@@ -5,15 +5,10 @@ import kotlinx.serialization.Serializable
 
 @Entity(tableName = "materials")
 @Serializable
-data class Material (
+data class Material(
     @PrimaryKey val id: DBid,
     val data: MaterialData
-) {
-    fun toXml() : String {
-        // TODO implement (it's not easy)
-        return "TODO"
-    }
-}
+)
 
 @Dao
 interface MaterialDao {
diff --git a/app/src/main/java/com/github/braillesystems/learnbraille/data/entities/StepData.kt b/app/src/main/java/com/github/braillesystems/learnbraille/data/entities/StepData.kt
index 2abe3126..1e70430d 100644
--- a/app/src/main/java/com/github/braillesystems/learnbraille/data/entities/StepData.kt
+++ b/app/src/main/java/com/github/braillesystems/learnbraille/data/entities/StepData.kt
@@ -13,7 +13,7 @@ import kotlinx.serialization.json.Json
  * All texts are in html format. Use .parseAsHtml android extension function.
  */
 @Serializable
-sealed class StepData : XmlAble
+sealed class StepData
 
 class StepDataConverters {
 
@@ -33,8 +33,7 @@ typealias HtmlText = String
  */
 @Serializable
 sealed class BaseInfo : StepData() {
-    override val xmlTag = "text"
-    override val xmlParams: Map<String, String> = mapOf("type" to "info")
+    abstract val text: HtmlText
 }
 
 /**
@@ -43,7 +42,7 @@ sealed class BaseInfo : StepData() {
 @Serializable
 data class Info(
     @SerialName("info")
-    override val xmlBody: HtmlText
+    override val text: HtmlText
 ) : BaseInfo()
 
 /**
@@ -52,7 +51,7 @@ data class Info(
 @Serializable
 data class FirstInfo(
     @SerialName("info")
-    override val xmlBody: HtmlText
+    override val text: HtmlText
 ) : BaseInfo()
 
 /**
@@ -61,14 +60,13 @@ data class FirstInfo(
 @Serializable
 data class LastInfo(
     @SerialName("info")
-    override val xmlBody: HtmlText
+    override val text: HtmlText
 ) : BaseInfo()
 
 
 @Serializable
 sealed class BaseInput : StepData() {
     abstract val brailleDots: BrailleDots
-    override val xmlTag: String = "practice"
 }
 
 /**
@@ -78,11 +76,6 @@ sealed class BaseInput : StepData() {
 data class Input(
     val material: Material
 ) : BaseInput() {
-    override val xmlParams: Map<String, String> = mapOf(
-        "type" to "practice",
-        "title" to ""
-    )
-    override val xmlBody: HtmlText = material.toXml()
 
     override val brailleDots: BrailleDots
         get() = when (material.data) {
@@ -98,22 +91,15 @@ data class Input(
  */
 @Serializable
 data class InputDots(
-    val text: HtmlText,
+    val text: HtmlText?,
     @SerialName("dots") // backward compatibility
     override val brailleDots: BrailleDots
-) : BaseInput() {
-    override val xmlParams: Map<String, String> = mapOf(
-        "type" to "practice",
-        "title" to text
-    )
-    override val xmlBody: HtmlText = brailleDots.toXml()
-}
+) : BaseInput()
 
 
 @Serializable
 sealed class BaseShow : StepData() {
     abstract val brailleDots: BrailleDots
-    override val xmlTag = "reading"
 }
 
 /**
@@ -127,11 +113,6 @@ data class Show(
         get() = when (material.data) {
             is OneBrailleSymbol -> material.data.brailleDots
         }
-    override val xmlParams: Map<String, String> = mapOf(
-        "type" to "reading",
-        "title" to ""
-    )
-    override val xmlBody: HtmlText = material.toXml()
 }
 
 /**
@@ -142,13 +123,7 @@ data class Show(
  */
 @Serializable
 data class ShowDots(
-    val text: HtmlText,
+    val text: HtmlText?,
     @SerialName("dots")
     override val brailleDots: BrailleDots
-) : BaseShow() {
-    override val xmlParams: Map<String, String> = mapOf(
-        "type" to "reading",
-        "title" to text
-    )
-    override val xmlBody: HtmlText = brailleDots.toXml()
-}
+) : BaseShow()
diff --git a/app/src/main/java/com/github/braillesystems/learnbraille/ui/screens/theory/steps/info/AbstractInfoStepFragment.kt b/app/src/main/java/com/github/braillesystems/learnbraille/ui/screens/theory/steps/info/AbstractInfoStepFragment.kt
index f0598ce0..60c05a0e 100644
--- a/app/src/main/java/com/github/braillesystems/learnbraille/ui/screens/theory/steps/info/AbstractInfoStepFragment.kt
+++ b/app/src/main/java/com/github/braillesystems/learnbraille/ui/screens/theory/steps/info/AbstractInfoStepFragment.kt
@@ -11,7 +11,7 @@ abstract class AbstractInfoStepFragment(helpMsgId: HelpMsgId) : AbstractStepFrag
     override fun iniStepHelper() {
         val data = step.data
         require(data is BaseInfo)
-        stepBinding.textView?.text = data.xmlBody.parseAsHtml()
-        checkedAnnounce(data.xmlBody)
+        stepBinding.textView?.text = data.text.parseAsHtml()
+        checkedAnnounce(data.text)
     }
 }
diff --git a/app/src/main/java/com/github/braillesystems/learnbraille/ui/screens/theory/steps/input/InputDotsFragment.kt b/app/src/main/java/com/github/braillesystems/learnbraille/ui/screens/theory/steps/input/InputDotsFragment.kt
index f541ea05..6d50deac 100644
--- a/app/src/main/java/com/github/braillesystems/learnbraille/ui/screens/theory/steps/input/InputDotsFragment.kt
+++ b/app/src/main/java/com/github/braillesystems/learnbraille/ui/screens/theory/steps/input/InputDotsFragment.kt
@@ -52,7 +52,7 @@ class InputDotsFragment : AbstractInputStepFragment(R.string.lessons_help_input_
 
         val data = step.data
         require(data is InputDots)
-        val text = data.xmlBody
+        val text = data.text
             ?: getString(R.string.lessons_show_dots_info_template).format(data.brailleDots.spelling)
         infoTextView.text = text.parseAsHtml()
         checkedAnnounce(text.removeHtmlMarkup())
diff --git a/app/src/main/java/com/github/braillesystems/learnbraille/ui/screens/theory/steps/show/ShowDotsFragment.kt b/app/src/main/java/com/github/braillesystems/learnbraille/ui/screens/theory/steps/show/ShowDotsFragment.kt
index 247241c2..94ad8fff 100644
--- a/app/src/main/java/com/github/braillesystems/learnbraille/ui/screens/theory/steps/show/ShowDotsFragment.kt
+++ b/app/src/main/java/com/github/braillesystems/learnbraille/ui/screens/theory/steps/show/ShowDotsFragment.kt
@@ -44,7 +44,7 @@ class ShowDotsFragment : AbstractShowStepFragment(R.string.lessons_help_show_dot
 
         val data = step.data
         require(data is ShowDots)
-        val text = data.xmlBody
+        val text = data.text
             ?: getString(R.string.lessons_show_dots_info_template).format(data.brailleDots.spelling)
         infoTextView.text = text.parseAsHtml()
         checkedAnnounce(text.removeHtmlMarkup())
diff --git a/app/src/test/java/com/github/braillesystems/learnbraille/data/entities/ToXmlTest.kt b/app/src/test/java/com/github/braillesystems/learnbraille/data/entities/ToXmlTest.kt
index 1c4b17e4..fc3b03c5 100644
--- a/app/src/test/java/com/github/braillesystems/learnbraille/data/entities/ToXmlTest.kt
+++ b/app/src/test/java/com/github/braillesystems/learnbraille/data/entities/ToXmlTest.kt
@@ -16,20 +16,70 @@ internal val testLessons by lessons {
     }
 }
 
+internal fun toXml(brailleDots: BrailleDots): HtmlText {
+    val dotsSymbols = brailleDots.toString().replace("F", "T").replace("E", "F")
+    var result = ""
+    dotsSymbols.dropLast(1).forEach { result += "$it, " }
+    result += dotsSymbols.takeLast(1)
+    return "($result)"
+}
+
+internal fun toXml(material: Material): HtmlText {
+    return "TODO" // TODO (not easy)
+}
+
+internal fun toXml(stepData: StepData): HtmlText =
+    when (stepData) {
+        is BaseInfo -> object : XmlAble {
+            override val xmlTag: String = "text"
+            override val xmlParams: Map<String, String> = mapOf("type" to "info")
+            override val xmlBody: HtmlText = stepData.text
+        }
+        is BaseInput -> object : XmlAble {
+            override val xmlTag: String = "practice"
+            override val xmlParams = mapOf(
+                "type" to "practice",
+                "title" to if (stepData is InputDots) stepData.text ?: "" else ""
+            )
+            override val xmlBody: HtmlText = when (stepData) {
+                is InputDots -> toXml(stepData.brailleDots)
+                is Input -> toXml(stepData.material)
+                else -> "toXml not implemented for this class"
+            }
+        }
+        is BaseShow -> object : XmlAble {
+            override val xmlTag: String = "reading"
+            override val xmlParams = mapOf(
+                "type" to "reading",
+                "title" to if (stepData is ShowDots) stepData.text ?: "" else ""
+            )
+            override val xmlBody: HtmlText = when (stepData) {
+                is ShowDots -> toXml(stepData.brailleDots)
+                is Input -> toXml(stepData.material)
+                else -> "toXml not implemented for this class"
+            }
+        }
+        else -> object : XmlAble {
+            override val xmlTag: String = stepData.toString()
+            override val xmlParams: Map<String, String> = mapOf()
+            override val xmlBody: HtmlText = "toXml not implemented for this class"
+        }
+    }.toXml()
+
 internal fun toXml(lesson: LessonWithSteps): HtmlText {
     return object : XmlAble {
         override val xmlTag: String = "lesson"
 
-        override val xmlParams: Map<String, String>
-            get() = mapOf("name" to lesson.first.name.replace("\"", "'"))
+        override val xmlParams: Map<String, String> =
+            mapOf("name" to lesson.first.name.replace("\"", "'"))
 
         override val xmlBody: HtmlText
             get() = {
-              var stepBuilder: HtmlText = ""
-                for(step in lesson.second.dropLast(1)){
-                    stepBuilder += (step.first.data.toXml() + "\n") // TODO [... <br>] -> [<p>...</p>]
+                var stepBuilder: HtmlText = ""
+                for (step in lesson.second.dropLast(1)) {
+                    stepBuilder += (toXml(step.first.data) + "\n") // TODO [... <br>] -> [<p>...</p>]
                 }
-                stepBuilder + lesson.second.takeLast(1)[0].first.data.toXml()
+                stepBuilder + toXml(lesson.second.takeLast(1)[0].first.data)
             }()
     }.toXml()
 }
@@ -46,7 +96,7 @@ class ToXmlTest {
                     to InputDots("type in these dots!", BrailleDots(E, E, F, E, E, F))
         )
         for ((expectedXml, stepData) in cases) {
-            assertEquals(expectedXml, stepData.toXml().replace("\n", ""))
+            assertEquals(expectedXml, toXml(stepData).replace("\n", ""))
         }
     }
 
@@ -55,7 +105,7 @@ class ToXmlTest {
         println(toXml(testLessons.lessons[0]))
 
         var xmlText = ""
-        for(lessons in golubinaIntroLessons.lessons) {
+        for (lessons in golubinaIntroLessons.lessons) {
             xmlText += (toXml(lessons) + "\n")
         }