diff --git a/CHANGELOG.md b/CHANGELOG.md
index 17b972cc..95d5c0d5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,8 @@
 - `ActiveDataSet` renamed to `DataSource`
 - `selectOne`->`getByType`
 - Data traversal in `DataSet` is done via iterator
+- Remove all unnecessary properties for `IOFormat`
+- Separate interfaces for `IOReader` and `IOWriter`
 
 ### Deprecated
 
diff --git a/build.gradle.kts b/build.gradle.kts
index a7560698..765e242f 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -1,3 +1,5 @@
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
 plugins {
     id("ru.mipt.npm.gradle.project")
 }
@@ -5,6 +7,12 @@ plugins {
 allprojects {
     group = "space.kscience"
     version = "0.6.0-dev-7"
+
+    tasks.withType<KotlinCompile>{
+        kotlinOptions{
+            freeCompilerArgs = freeCompilerArgs + "-Xcontext-receivers"
+        }
+    }
 }
 
 subprojects {
diff --git a/dataforge-context/src/commonMain/kotlin/space/kscience/dataforge/provider/Provider.kt b/dataforge-context/src/commonMain/kotlin/space/kscience/dataforge/provider/Provider.kt
index e1940958..c91c2e4f 100644
--- a/dataforge-context/src/commonMain/kotlin/space/kscience/dataforge/provider/Provider.kt
+++ b/dataforge-context/src/commonMain/kotlin/space/kscience/dataforge/provider/Provider.kt
@@ -75,10 +75,8 @@ public inline fun <reified T : Any> Provider.provide(path: String, targetOverrid
 /**
  *  Typed top level content
  */
-public fun <T : Any> Provider.top(target: String, type: KClass<out T>): Map<Name, T> {
-    return content(target).mapValues {
-        type.safeCast(it.value) ?: error("The type of element $it is ${it::class} but $type is expected")
-    }
+public fun <T : Any> Provider.top(target: String, type: KClass<out T>): Map<Name, T> = content(target).mapValues {
+    type.safeCast(it.value) ?: error("The type of element ${it.value} is ${it.value::class} but $type is expected")
 }
 
 /**
diff --git a/dataforge-io/dataforge-io-yaml/src/commonMain/kotlin/space/kscience/dataforge/io/yaml/FrontMatterEnvelopeFormat.kt b/dataforge-io/dataforge-io-yaml/src/commonMain/kotlin/space/kscience/dataforge/io/yaml/FrontMatterEnvelopeFormat.kt
index 7f705a71..244284c8 100644
--- a/dataforge-io/dataforge-io-yaml/src/commonMain/kotlin/space/kscience/dataforge/io/yaml/FrontMatterEnvelopeFormat.kt
+++ b/dataforge-io/dataforge-io-yaml/src/commonMain/kotlin/space/kscience/dataforge/io/yaml/FrontMatterEnvelopeFormat.kt
@@ -7,10 +7,7 @@ import io.ktor.utils.io.core.readBytes
 import space.kscience.dataforge.context.Context
 import space.kscience.dataforge.context.Global
 import space.kscience.dataforge.io.*
-import space.kscience.dataforge.io.IOFormat.Companion.META_KEY
-import space.kscience.dataforge.io.IOFormat.Companion.NAME_KEY
 import space.kscience.dataforge.meta.Meta
-import space.kscience.dataforge.misc.DFExperimental
 import space.kscience.dataforge.names.Name
 import space.kscience.dataforge.names.plus
 
@@ -65,11 +62,6 @@ public class FrontMatterEnvelopeFormat(
         }
     }
 
-    override fun toMeta(): Meta = Meta {
-        NAME_KEY put name.toString()
-        META_KEY put meta
-    }
-
     public companion object : EnvelopeFormatFactory {
         public const val SEPARATOR: String = "---"
 
diff --git a/dataforge-io/dataforge-io-yaml/src/commonMain/kotlin/space/kscience/dataforge/io/yaml/YamlMetaFormat.kt b/dataforge-io/dataforge-io-yaml/src/commonMain/kotlin/space/kscience/dataforge/io/yaml/YamlMetaFormat.kt
index b7c7c3e4..fffaa45b 100644
--- a/dataforge-io/dataforge-io-yaml/src/commonMain/kotlin/space/kscience/dataforge/io/yaml/YamlMetaFormat.kt
+++ b/dataforge-io/dataforge-io-yaml/src/commonMain/kotlin/space/kscience/dataforge/io/yaml/YamlMetaFormat.kt
@@ -4,8 +4,6 @@ import io.ktor.utils.io.core.Input
 import io.ktor.utils.io.core.Output
 import net.mamoe.yamlkt.*
 import space.kscience.dataforge.context.Context
-import space.kscience.dataforge.io.IOFormat.Companion.META_KEY
-import space.kscience.dataforge.io.IOFormat.Companion.NAME_KEY
 import space.kscience.dataforge.io.MetaFormat
 import space.kscience.dataforge.io.MetaFormatFactory
 import space.kscience.dataforge.io.readUtf8String
@@ -14,7 +12,6 @@ import space.kscience.dataforge.meta.Meta
 import space.kscience.dataforge.meta.descriptors.MetaDescriptor
 import space.kscience.dataforge.meta.descriptors.get
 import space.kscience.dataforge.meta.isLeaf
-import space.kscience.dataforge.misc.DFExperimental
 import space.kscience.dataforge.names.NameToken
 import space.kscience.dataforge.names.withIndex
 import space.kscience.dataforge.values.ListValue
@@ -108,11 +105,6 @@ public class YamlMetaFormat(private val meta: Meta) : MetaFormat {
         return yaml.toMeta()
     }
 
-    override fun toMeta(): Meta = Meta {
-        NAME_KEY put FrontMatterEnvelopeFormat.name.toString()
-        META_KEY put meta
-    }
-
     public companion object : MetaFormatFactory {
         override fun build(context: Context, meta: Meta): MetaFormat = YamlMetaFormat(meta)
 
diff --git a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/EnvelopeFormat.kt b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/EnvelopeFormat.kt
index 4dea572b..b705a3c0 100644
--- a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/EnvelopeFormat.kt
+++ b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/EnvelopeFormat.kt
@@ -17,8 +17,6 @@ import kotlin.reflect.typeOf
 public data class PartialEnvelope(val meta: Meta, val dataOffset: Int, val dataSize: ULong?)
 
 public interface EnvelopeFormat : IOFormat<Envelope> {
-    override val type: KType get() = typeOf<Envelope>()
-
     public val defaultMetaFormat: MetaFormatFactory get() = JsonMetaFormat
 
     public fun readPartial(input: Input): PartialEnvelope
diff --git a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/EnvelopeParts.kt b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/EnvelopeParts.kt
index 641247c3..72e9dfd4 100644
--- a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/EnvelopeParts.kt
+++ b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/EnvelopeParts.kt
@@ -1,5 +1,6 @@
 package space.kscience.dataforge.io
 
+import space.kscience.dataforge.context.invoke
 import space.kscience.dataforge.io.Envelope.Companion.ENVELOPE_NODE_KEY
 import space.kscience.dataforge.io.PartDescriptor.Companion.DEFAULT_MULTIPART_DATA_SEPARATOR
 import space.kscience.dataforge.io.PartDescriptor.Companion.MULTIPART_DATA_TYPE
@@ -35,7 +36,7 @@ public typealias EnvelopeParts = List<EnvelopePart>
 
 public fun EnvelopeBuilder.multipart(
     parts: EnvelopeParts,
-    separator: String = DEFAULT_MULTIPART_DATA_SEPARATOR
+    separator: String = DEFAULT_MULTIPART_DATA_SEPARATOR,
 ) {
     dataType = MULTIPART_DATA_TYPE
 
@@ -67,17 +68,25 @@ public fun EnvelopeBuilder.multipart(
     }
 }
 
+/**
+ * Put a list of envelopes as parts of given envelope
+ */
 public fun EnvelopeBuilder.envelopes(
     envelopes: List<Envelope>,
-    format: EnvelopeFormat = TaggedEnvelopeFormat,
-    separator: String = DEFAULT_MULTIPART_DATA_SEPARATOR
+    formatFactory: EnvelopeFormatFactory = TaggedEnvelopeFormat,
+    formatMeta: Meta? = null,
+    separator: String = DEFAULT_MULTIPART_DATA_SEPARATOR,
 ) {
     val parts = envelopes.map {
-        val binary = format.toBinary(it)
+        val format = formatMeta?.let { formatFactory(formatMeta) } ?: formatFactory
+        val binary = Binary(it, format)
         EnvelopePart(binary, null)
     }
-    meta{
-        set(MULTIPART_KEY + PART_FORMAT_KEY, format.toMeta())
+    meta {
+        (MULTIPART_KEY + PART_FORMAT_KEY) put {
+            IOFormatFactory.NAME_KEY put formatFactory.name.toString()
+            formatMeta?.let { IOFormatFactory.META_KEY put formatMeta }
+        }
     }
     multipart(parts, separator)
 }
diff --git a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/IOFormat.kt b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/IOFormat.kt
index 7c3f8988..985a1e69 100644
--- a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/IOFormat.kt
+++ b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/IOFormat.kt
@@ -1,12 +1,13 @@
 package space.kscience.dataforge.io
 
-import io.ktor.utils.io.core.*
+import io.ktor.utils.io.core.Input
+import io.ktor.utils.io.core.Output
+import io.ktor.utils.io.core.readDouble
+import io.ktor.utils.io.core.writeDouble
 import space.kscience.dataforge.context.Context
 import space.kscience.dataforge.context.Factory
-import space.kscience.dataforge.io.IOFormat.Companion.NAME_KEY
 import space.kscience.dataforge.io.IOFormatFactory.Companion.IO_FORMAT_TYPE
 import space.kscience.dataforge.meta.Meta
-import space.kscience.dataforge.meta.MetaRepr
 import space.kscience.dataforge.misc.Named
 import space.kscience.dataforge.misc.Type
 import space.kscience.dataforge.names.Name
@@ -14,92 +15,53 @@ import space.kscience.dataforge.names.asName
 import kotlin.reflect.KType
 import kotlin.reflect.typeOf
 
+public fun interface IOReader<out T : Any> {
+
+    public fun readObject(input: Input): T
+}
+
+public fun interface IOWriter<in T : Any> {
+    public fun writeObject(output: Output, obj: T)
+}
+
+
 /**
  * And interface for reading and writing objects into with IO streams
  */
-public interface IOFormat<T : Any> : MetaRepr {
-    public val type: KType
+public interface IOFormat<T : Any> : IOReader<T>, IOWriter<T>
 
-    public fun writeObject(output: Output, obj: T)
-    public fun readObject(input: Input): T
+public fun <T : Any> Input.readObject(format: IOReader<T>): T = format.readObject(this@readObject)
 
-    public companion object {
-        public val NAME_KEY: Name = "name".asName()
-        public val META_KEY: Name = "meta".asName()
-    }
-}
-
-public fun <T : Any> Input.readWith(format: IOFormat<T>): T = format.readObject(this@readWith)
-
-public fun <T: Any> IOFormat<T>.readObject(binary: Binary): T = binary.read {
+public fun <T : Any> IOFormat<T>.readObjectFrom(binary: Binary): T = binary.read {
     readObject(this)
 }
 
 /**
  * Read given binary as object using given format
  */
-public fun <T : Any> Binary.readWith(format: IOFormat<T>): T = read {
-    readWith(format)
+public fun <T : Any> Binary.readWith(format: IOReader<T>): T = read {
+    readObject(format)
 }
 
-public fun <T : Any> Output.writeWith(format: IOFormat<T>, obj: T): Unit =
-    format.run { writeObject(this@writeWith, obj) }
+public fun <T : Any> Output.writeObject(format: IOWriter<T>, obj: T): Unit =
+    format.run { writeObject(this@writeObject, obj) }
 
-public inline fun <reified T : Any> IOFormat.Companion.listOf(
-    format: IOFormat<T>,
-): IOFormat<List<T>> = object : IOFormat<List<T>> {
-    override val type: KType = typeOf<List<T>>()
-
-    override fun writeObject(output: Output, obj: List<T>) {
-        output.writeInt(obj.size)
-        format.run {
-            obj.forEach {
-                writeObject(output, it)
-            }
-        }
-    }
-
-    override fun readObject(input: Input): List<T> {
-        val size = input.readInt()
-        return format.run {
-            List(size) { readObject(input) }
-        }
-    }
-
-    override fun toMeta(): Meta = Meta {
-        NAME_KEY put "list"
-        "contentFormat" put format.toMeta()
-    }
-
-}
-
-//public fun ObjectPool<Buffer>.fill(block: Buffer.() -> Unit): Buffer {
-//    val buffer = borrow()
-//    return try {
-//        buffer.apply(block)
-//    } catch (ex: Exception) {
-//        //recycle(buffer)
-//        throw ex
-//    }
-//}
 
 @Type(IO_FORMAT_TYPE)
-public interface IOFormatFactory<T : Any> : Factory<IOFormat<T>>, Named, MetaRepr {
+public interface IOFormatFactory<T : Any> : Factory<IOFormat<T>>, Named {
     /**
      * Explicit type for dynamic type checks
      */
     public val type: KType
 
-    override fun toMeta(): Meta = Meta {
-        NAME_KEY put name.toString()
-    }
-
     public companion object {
         public const val IO_FORMAT_TYPE: String = "io.format"
+        public val NAME_KEY: Name = "name".asName()
+        public val META_KEY: Name = "meta".asName()
     }
 }
 
-public fun <T : Any> IOFormat<T>.toBinary(obj: T): Binary = Binary { writeObject(this, obj) }
+public fun <T : Any> Binary(obj: T, format: IOWriter<T>): Binary = Binary { format.writeObject(this, obj) }
 
 public object DoubleIOFormat : IOFormat<Double>, IOFormatFactory<Double> {
     override fun build(context: Context, meta: Meta): IOFormat<Double> = this
@@ -113,21 +75,4 @@ public object DoubleIOFormat : IOFormat<Double>, IOFormatFactory<Double> {
     }
 
     override fun readObject(input: Input): Double = input.readDouble()
-}
-
-//public object ValueIOFormat : IOFormat<Value>, IOFormatFactory<Value> {
-//    override fun invoke(meta: Meta, context: Context): IOFormat<Value> = this
-//
-//    override val name: Name = "value".asName()
-//
-//    override val type: KType get() = typeOf<Value>()
-//
-//    override fun writeObject(output: Output, obj: Value) {
-//        BinaryMetaFormat.run { output.writeValue(obj) }
-//    }
-//
-//    override fun readObject(input: Input): Value {
-//        return (BinaryMetaFormat.run { input.readMetaItem() } as? MetaItemValue)?.value
-//            ?: error("The item is not a value")
-//    }
-//}
\ No newline at end of file
+}
\ No newline at end of file
diff --git a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/IOPlugin.kt b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/IOPlugin.kt
index 9e1f0dd1..dc6541f2 100644
--- a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/IOPlugin.kt
+++ b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/IOPlugin.kt
@@ -2,8 +2,6 @@ package space.kscience.dataforge.io
 
 import space.kscience.dataforge.context.*
 import space.kscience.dataforge.io.EnvelopeFormatFactory.Companion.ENVELOPE_FORMAT_TYPE
-import space.kscience.dataforge.io.IOFormat.Companion.META_KEY
-import space.kscience.dataforge.io.IOFormat.Companion.NAME_KEY
 import space.kscience.dataforge.io.IOFormatFactory.Companion.IO_FORMAT_TYPE
 import space.kscience.dataforge.io.MetaFormatFactory.Companion.META_FORMAT_TYPE
 import space.kscience.dataforge.meta.Meta
@@ -20,12 +18,12 @@ public class IOPlugin(meta: Meta) : AbstractPlugin(meta) {
     }
 
     public fun <T : Any> resolveIOFormat(item: Meta, type: KClass<out T>): IOFormat<T>? {
-        val key = item.string ?: item[NAME_KEY]?.string ?: error("Format name not defined")
+        val key = item.string ?: item[IOFormatFactory.NAME_KEY]?.string ?: error("Format name not defined")
         val name = Name.parse(key)
         return ioFormatFactories.find { it.name == name }?.let {
             @Suppress("UNCHECKED_CAST")
             if (it.type != type) error("Format type ${it.type} is not the same as requested type $type")
-            else it.build(context, item[META_KEY] ?: Meta.EMPTY) as IOFormat<T>
+            else it.build(context, item[IOFormatFactory.META_KEY] ?: Meta.EMPTY) as IOFormat<T>
         }
     }
 
@@ -47,8 +45,8 @@ public class IOPlugin(meta: Meta) : AbstractPlugin(meta) {
         envelopeFormatFactories.find { it.name == name }?.build(context, meta)
 
     public fun resolveEnvelopeFormat(item: Meta): EnvelopeFormat? {
-        val name = item.string ?: item[NAME_KEY]?.string ?: error("Envelope format name not defined")
-        val meta = item[META_KEY] ?: Meta.EMPTY
+        val name = item.string ?: item[IOFormatFactory.NAME_KEY]?.string ?: error("Envelope format name not defined")
+        val meta = item[IOFormatFactory.META_KEY] ?: Meta.EMPTY
         return resolveEnvelopeFormat(Name.parse(name), meta)
     }
 
diff --git a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/JsonMetaFormat.kt b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/JsonMetaFormat.kt
index d5beee22..4bb3c82d 100644
--- a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/JsonMetaFormat.kt
+++ b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/JsonMetaFormat.kt
@@ -8,30 +8,21 @@ import io.ktor.utils.io.core.Output
 import kotlinx.serialization.json.Json
 import kotlinx.serialization.json.JsonObject
 import space.kscience.dataforge.context.Context
-import space.kscience.dataforge.io.IOFormat.Companion.NAME_KEY
 import space.kscience.dataforge.meta.Meta
 import space.kscience.dataforge.meta.descriptors.MetaDescriptor
 import space.kscience.dataforge.meta.toJson
 import space.kscience.dataforge.meta.toMeta
-import kotlin.reflect.KType
-import kotlin.reflect.typeOf
 
 /**
  * A Json format for Meta representation
  */
 public class JsonMetaFormat(private val json: Json = DEFAULT_JSON) : MetaFormat {
 
-    override val type: KType get() = typeOf<Meta>()
-
     override fun writeMeta(output: Output, meta: Meta, descriptor: MetaDescriptor?) {
         val jsonObject = meta.toJson(descriptor)
         output.writeUtf8String(json.encodeToString(JsonObject.serializer(), jsonObject))
     }
 
-    override fun toMeta(): Meta = Meta {
-        NAME_KEY put name.toString()
-    }
-
     override fun readMeta(input: Input, descriptor: MetaDescriptor?): Meta {
         val str = input.readUtf8String()//readByteArray().decodeToString()
         val jsonElement = json.parseToJsonElement(str)
diff --git a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/MetaFormat.kt b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/MetaFormat.kt
index 46d7b540..5e009a12 100644
--- a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/MetaFormat.kt
+++ b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/MetaFormat.kt
@@ -20,7 +20,6 @@ import kotlin.reflect.typeOf
  * A format for meta serialization
  */
 public interface MetaFormat : IOFormat<Meta> {
-    override val type: KType get() = typeOf<Meta>()
 
     override fun writeObject(output: Output, obj: Meta) {
         writeMeta(output, obj, null)
diff --git a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/TaggedEnvelopeFormat.kt b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/TaggedEnvelopeFormat.kt
index 933dc343..2e5d3cc6 100644
--- a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/TaggedEnvelopeFormat.kt
+++ b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/TaggedEnvelopeFormat.kt
@@ -3,8 +3,6 @@ package space.kscience.dataforge.io
 import io.ktor.utils.io.core.*
 import space.kscience.dataforge.context.Context
 import space.kscience.dataforge.context.Global
-import space.kscience.dataforge.io.IOFormat.Companion.META_KEY
-import space.kscience.dataforge.io.IOFormat.Companion.NAME_KEY
 import space.kscience.dataforge.meta.Meta
 import space.kscience.dataforge.meta.enum
 import space.kscience.dataforge.meta.get
@@ -49,7 +47,7 @@ public class TaggedEnvelopeFormat(
         formatMeta: Meta,
     ) {
         val metaFormat = metaFormatFactory.build(this@TaggedEnvelopeFormat.io.context, formatMeta)
-        val metaBytes = metaFormat.toBinary(envelope.meta)
+        val metaBytes = Binary(envelope.meta,metaFormat)
         val actualSize: ULong = (envelope.data?.size ?: 0).toULong()
         val tag = Tag(metaFormatFactory.key, metaBytes.size.toUInt() + 2u, actualSize)
         output.writeBinary(tag.toBinary())
@@ -74,7 +72,7 @@ public class TaggedEnvelopeFormat(
 
         val metaBinary = input.readBinary(tag.metaSize.toInt())
 
-        val meta: Meta = metaFormat.readObject(metaBinary)
+        val meta: Meta = metaFormat.readObjectFrom(metaBinary)
 
         val data = input.readBinary(tag.dataSize.toInt())
 
@@ -89,7 +87,7 @@ public class TaggedEnvelopeFormat(
 
         val metaBinary = input.readBinary(tag.metaSize.toInt())
 
-        val meta: Meta = metaFormat.readObject(metaBinary)
+        val meta: Meta = metaFormat.readObjectFrom(metaBinary)
 
 
         return PartialEnvelope(meta, (version.tagSize + tag.metaSize).toInt(), tag.dataSize)
@@ -106,13 +104,6 @@ public class TaggedEnvelopeFormat(
         DF03(24u)
     }
 
-    override fun toMeta(): Meta = Meta {
-        NAME_KEY put name.toString()
-        META_KEY put {
-            "version" put version
-        }
-    }
-
     public companion object : EnvelopeFormatFactory {
         private const val START_SEQUENCE = "#~"
         private const val END_SEQUENCE = "~#\r\n"
diff --git a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/TaglessEnvelopeFormat.kt b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/TaglessEnvelopeFormat.kt
index 9a0f4a98..4e2bacfc 100644
--- a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/TaglessEnvelopeFormat.kt
+++ b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/TaglessEnvelopeFormat.kt
@@ -3,8 +3,6 @@ package space.kscience.dataforge.io
 import io.ktor.utils.io.core.*
 import space.kscience.dataforge.context.Context
 import space.kscience.dataforge.context.Global
-import space.kscience.dataforge.io.IOFormat.Companion.META_KEY
-import space.kscience.dataforge.io.IOFormat.Companion.NAME_KEY
 import space.kscience.dataforge.meta.Meta
 import space.kscience.dataforge.meta.get
 import space.kscience.dataforge.meta.isEmpty
@@ -50,11 +48,11 @@ public class TaglessEnvelopeFormat(
 
         //Printing meta
         if (!envelope.meta.isEmpty()) {
-            val metaBytes = metaFormat.toBinary(envelope.meta)
+            val metaBinary = Binary(envelope.meta, metaFormat)
             output.writeProperty(META_LENGTH_PROPERTY,
-                metaBytes.size + 2)
+                metaBinary.size + 2)
             output.writeUtf8String(this.metaStart + "\r\n")
-            output.writeBinary(metaBytes)
+            output.writeBinary(metaBinary)
             output.writeRawString("\r\n")
         }
 
@@ -102,7 +100,7 @@ public class TaglessEnvelopeFormat(
             val metaFormat = properties[META_TYPE_PROPERTY]?.let { io.resolveMetaFormat(it) } ?: JsonMetaFormat
             val metaSize = properties[META_LENGTH_PROPERTY]?.toInt()
             meta = if (metaSize != null) {
-                metaFormat.readObject(input.readBinary(metaSize))
+                metaFormat.readObjectFrom(input.readBinary(metaSize))
             } else {
                 error("Can't partially read an envelope with undefined meta size")
             }
@@ -170,7 +168,7 @@ public class TaglessEnvelopeFormat(
             val metaSize = properties[META_LENGTH_PROPERTY]?.toInt()
             meta = if (metaSize != null) {
                 offset += metaSize
-                metaFormat.readObject(input.readBinary(metaSize))
+                metaFormat.readObjectFrom(input.readBinary(metaSize))
             } else {
                 error("Can't partially read an envelope with undefined meta size")
             }
@@ -187,11 +185,6 @@ public class TaglessEnvelopeFormat(
         return PartialEnvelope(meta, offset, dataSize)
     }
 
-    override fun toMeta(): Meta = Meta {
-        NAME_KEY put name.toString()
-        META_KEY put meta
-    }
-
     public companion object : EnvelopeFormatFactory {
 
         private val propertyPattern = "#\\?\\s*([\\w.]*)\\s*:\\s*([^;]*);?".toRegex()
diff --git a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/ioMisc.kt b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/ioMisc.kt
index e72c0eed..5c17e9ac 100644
--- a/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/ioMisc.kt
+++ b/dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/ioMisc.kt
@@ -183,7 +183,7 @@ public fun Input.discardWithSeparator(
     atMost: Int = Int.MAX_VALUE,
     skipUntilEndOfLine: Boolean = false,
 ): Int {
-    val dummy: Output = object :Output(ChunkBuffer.Pool){
+    val dummy: Output = object : Output(ChunkBuffer.Pool) {
         override fun closeDestination() {
             // Do nothing
         }
diff --git a/dataforge-io/src/commonTest/kotlin/space/kscience/dataforge/io/MultipartTest.kt b/dataforge-io/src/commonTest/kotlin/space/kscience/dataforge/io/MultipartTest.kt
index 8ffaef14..6315d744 100644
--- a/dataforge-io/src/commonTest/kotlin/space/kscience/dataforge/io/MultipartTest.kt
+++ b/dataforge-io/src/commonTest/kotlin/space/kscience/dataforge/io/MultipartTest.kt
@@ -32,18 +32,17 @@ class MultipartTest {
 
     @Test
     fun testParts() {
-        TaglessEnvelopeFormat.run {
-            val singleEnvelopeData = toBinary(envelopes[0])
-            val singleEnvelopeSize = singleEnvelopeData.size
-            val bytes = toBinary(partsEnvelope)
-            assertTrue(envelopes.size * singleEnvelopeSize < bytes.size)
-            val reconstructed = bytes.readWith(this)
-            println(reconstructed.meta)
-            val parts = reconstructed.parts()
-            val envelope = parts[2].envelope(io)
-            assertEquals(2, envelope.meta["value"].int)
-            println(reconstructed.data!!.size)
-        }
+        val format = TaglessEnvelopeFormat
+        val singleEnvelopeData = Binary(envelopes[0], format)
+        val singleEnvelopeSize = singleEnvelopeData.size
+        val bytes = Binary(partsEnvelope, format)
+        assertTrue(envelopes.size * singleEnvelopeSize < bytes.size)
+        val reconstructed = bytes.readWith(format)
+        println(reconstructed.meta)
+        val parts = reconstructed.parts()
+        val envelope = parts[2].envelope(io)
+        assertEquals(2, envelope.meta["value"].int)
+        println(reconstructed.data!!.size)
     }
 
 }
\ No newline at end of file
diff --git a/dataforge-io/src/jvmMain/kotlin/space/kscience/dataforge/io/fileIO.kt b/dataforge-io/src/jvmMain/kotlin/space/kscience/dataforge/io/fileIO.kt
index 1f2d3041..64f4907e 100644
--- a/dataforge-io/src/jvmMain/kotlin/space/kscience/dataforge/io/fileIO.kt
+++ b/dataforge-io/src/jvmMain/kotlin/space/kscience/dataforge/io/fileIO.kt
@@ -97,7 +97,36 @@ public val IOPlugin.Companion.DATA_FILE_NAME: String get() = "@data"
 
 /**
  * Read file containing meta using given [formatOverride] or file extension to infer meta type.
- * If [path] is a directory search for file starting with `meta` in it
+ * If [path] is a directory search for file starting with `meta` in it.
+ *
+ * Returns null if meta could not be resolved
+ */
+public fun IOPlugin.readMetaFileOrNull(
+    path: Path,
+    formatOverride: MetaFormat? = null,
+    descriptor: MetaDescriptor? = null,
+): Meta? {
+    if (!Files.exists(path)) return null
+
+    val actualPath: Path = if (Files.isDirectory(path)) {
+        Files.list(path).asSequence().find { it.fileName.startsWith(IOPlugin.META_FILE_NAME) }
+            ?: return null
+    } else {
+        path
+    }
+    val extension = actualPath.fileName.toString().substringAfterLast('.')
+
+    val metaFormat = formatOverride ?: resolveMetaFormat(extension) ?: return null
+    return actualPath.read {
+        metaFormat.readMeta(this, descriptor)
+    }
+}
+
+/**
+ * Read file containing meta using given [formatOverride] or file extension to infer meta type.
+ * If [path] is a directory search for file starting with `meta` in it.
+ *
+ * Fails if nothing works.
  */
 public fun IOPlugin.readMetaFile(
     path: Path,
@@ -120,6 +149,7 @@ public fun IOPlugin.readMetaFile(
     }
 }
 
+
 /**
  * Write meta to file using [metaFormat]. If [path] is a directory, write a file with name equals name of [metaFormat].
  * Like "meta.json"
@@ -196,22 +226,11 @@ public fun IOPlugin.readEnvelopeFile(
         return SimpleEnvelope(meta, data)
     }
 
-    return formatPicker(path)?.let { format ->
-        format.readFile(path)
-    } ?: if (readNonEnvelopes) { // if no format accepts file, read it as binary
+    return formatPicker(path)?.readFile(path) ?: if (readNonEnvelopes) { // if no format accepts file, read it as binary
         SimpleEnvelope(Meta.EMPTY, path.asBinary())
     } else error("Can't infer format for file $path")
 }
 
-/**
- * Write a binary into file. Throws an error if file already exists
- */
-public fun <T : Any> IOFormat<T>.writeToFile(path: Path, obj: T) {
-    path.write {
-        writeObject(this, obj)
-    }
-}
-
 /**
  * Write envelope file to given [path] using [envelopeFormat] and optional [metaFormat]
  */
diff --git a/dataforge-workspace/src/commonMain/kotlin/space/kscience/dataforge/workspace/envelopeData.kt b/dataforge-workspace/src/commonMain/kotlin/space/kscience/dataforge/workspace/envelopeData.kt
index 55c98352..ce5be133 100644
--- a/dataforge-workspace/src/commonMain/kotlin/space/kscience/dataforge/workspace/envelopeData.kt
+++ b/dataforge-workspace/src/commonMain/kotlin/space/kscience/dataforge/workspace/envelopeData.kt
@@ -4,19 +4,18 @@ import space.kscience.dataforge.data.Data
 import space.kscience.dataforge.data.await
 import space.kscience.dataforge.io.*
 import space.kscience.dataforge.misc.DFInternal
+import kotlin.reflect.typeOf
 
 /**
  * Convert an [Envelope] to a data via given format. The actual parsing is done lazily.
  */
 @OptIn(DFInternal::class)
-public fun <T : Any> Envelope.toData(format: IOFormat<T>): Data<T> {
-    return Data(format.type, meta) {
-        data?.readWith(format) ?: error("Can't convert envelope without data to Data")
-    }
+public inline fun <reified T : Any> Envelope.toData(format: IOReader<T>): Data<T> = Data(typeOf<T>(), meta) {
+    data?.readWith(format) ?: error("Can't convert envelope without data to Data")
 }
 
-public suspend fun <T : Any> Data<T>.toEnvelope(format: IOFormat<T>): Envelope {
+public suspend fun <T : Any> Data<T>.toEnvelope(format: IOWriter<T>): Envelope {
     val obj = await()
-    val binary = format.toBinary(obj)
+    val binary = Binary(obj, format)
     return SimpleEnvelope(meta, binary)
 }
\ No newline at end of file
diff --git a/dataforge-workspace/src/jvmMain/kotlin/space/kscience/dataforge/workspace/fileData.kt b/dataforge-workspace/src/jvmMain/kotlin/space/kscience/dataforge/workspace/fileData.kt
index d758c45c..aa3ddede 100644
--- a/dataforge-workspace/src/jvmMain/kotlin/space/kscience/dataforge/workspace/fileData.kt
+++ b/dataforge-workspace/src/jvmMain/kotlin/space/kscience/dataforge/workspace/fileData.kt
@@ -2,11 +2,12 @@ package space.kscience.dataforge.workspace
 
 import io.ktor.utils.io.streams.asOutput
 import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.runBlocking
 import kotlinx.coroutines.withContext
 import space.kscience.dataforge.data.*
 import space.kscience.dataforge.io.*
-import space.kscience.dataforge.meta.*
+import space.kscience.dataforge.meta.Meta
+import space.kscience.dataforge.meta.get
+import space.kscience.dataforge.meta.string
 import space.kscience.dataforge.misc.DFExperimental
 import java.nio.file.FileSystem
 import java.nio.file.Files
@@ -15,28 +16,13 @@ import java.nio.file.StandardOpenOption
 import java.nio.file.spi.FileSystemProvider
 import java.util.zip.ZipEntry
 import java.util.zip.ZipOutputStream
-import kotlin.reflect.KType
-import kotlin.reflect.typeOf
 import kotlin.streams.toList
 
 //public typealias FileFormatResolver<T> = (Path, Meta) -> IOFormat<T>
 
-public interface FileFormatResolver<T : Any> {
-    public val type: KType
-    public operator fun invoke(path: Path, meta: Meta): IOFormat<T>
-}
+public typealias FileFormatResolver<T> = (path: Path, meta: Meta) -> IOReader<T>
 
 
-@PublishedApi
-internal inline fun <reified T : Any> IOPlugin.formatResolver(): FileFormatResolver<T> =
-    object : FileFormatResolver<T> {
-        override val type: KType = typeOf<T>()
-
-        @OptIn(DFExperimental::class)
-        override fun invoke(path: Path, meta: Meta): IOFormat<T> =
-            resolveIOFormat<T>() ?: error("Can't resolve IO format for ${T::class}")
-    }
-
 private fun newZFS(path: Path): FileSystem {
     val fsProvider = FileSystemProvider.installedProviders().find { it.scheme == "jar" }
         ?: error("Zip file system provider not found")
@@ -46,14 +32,9 @@ private fun newZFS(path: Path): FileSystem {
 /**
  * Read data with supported envelope format and binary format. If envelope format is null, then read binary directly from file.
  * The operation is blocking since it must read meta header. The reading of envelope body is lazy
- * @param type explicit type of data read
- * @param dataFormat binary format
- * @param envelopeFormat the format of envelope. If null, file is read directly
- * @param metaFile the relative file for optional meta override
- * @param metaFileFormat the meta format for override
  */
 @DFExperimental
-public fun <T : Any> IOPlugin.readDataFile(
+public inline fun <reified T : Any> IOPlugin.readDataFile(
     path: Path,
     formatResolver: FileFormatResolver<T>,
 ): Data<T> {
@@ -62,34 +43,26 @@ public fun <T : Any> IOPlugin.readDataFile(
     return envelope.toData(format)
 }
 
-@DFExperimental
-public inline fun <reified T : Any> IOPlugin.readDataFile(path: Path): Data<T> = readDataFile(path, formatResolver())
-
 /**
  * Add file/directory-based data tree item
  */
-@DFExperimental
-public suspend fun <T : Any> DataSetBuilder<T>.file(
-    plugin: IOPlugin,
+context(IOPlugin) @DFExperimental
+public fun DataSetBuilder<Any>.file(
     path: Path,
-    formatResolver: FileFormatResolver<T>,
+    formatResolver: FileFormatResolver<Any>,
 ) {
     //If path is a single file or a special directory, read it as single datum
     if (!Files.isDirectory(path) || Files.list(path).allMatch { it.fileName.toString().startsWith("@") }) {
-        plugin.run {
-            val data = readDataFile(path, formatResolver)
-            val name = data.meta[Envelope.ENVELOPE_NAME_KEY].string
-                ?: path.fileName.toString().replace(".df", "")
-            data(name, data)
-        }
+        val data = readDataFile(path, formatResolver)
+        val name = data.meta[Envelope.ENVELOPE_NAME_KEY].string
+            ?: path.fileName.toString().replace(".df", "")
+        data(name, data)
     } else {
         //otherwise, read as directory
-        plugin.run {
-            val data = readDataDirectory(path, formatResolver)
-            val name = data.meta[Envelope.ENVELOPE_NAME_KEY].string
-                ?: path.fileName.toString().replace(".df", "")
-            node(name, data)
-        }
+        val data = readDataDirectory(path, formatResolver)
+        val name = data.meta[Envelope.ENVELOPE_NAME_KEY].string
+            ?: path.fileName.toString().replace(".df", "")
+        node(name, data)
     }
 }
 
@@ -97,10 +70,10 @@ public suspend fun <T : Any> DataSetBuilder<T>.file(
  * Read the directory as a data node. If [path] is a zip archive, read it as directory
  */
 @DFExperimental
-public suspend fun <T : Any> IOPlugin.readDataDirectory(
+public fun IOPlugin.readDataDirectory(
     path: Path,
-    formatResolver: FileFormatResolver<T>,
-): DataTree<T> {
+    formatResolver: FileFormatResolver<Any>,
+): DataTree<Any> {
     //read zipped data node
     if (path.fileName != null && path.fileName.toString().endsWith(".zip")) {
         //Using explicit Zip file system to avoid bizarre compatibility bugs
@@ -108,24 +81,18 @@ public suspend fun <T : Any> IOPlugin.readDataDirectory(
         return readDataDirectory(fs.rootDirectories.first(), formatResolver)
     }
     if (!Files.isDirectory(path)) error("Provided path $path is not a directory")
-    return DataTree(formatResolver.type) {
+    return DataTree<Any> {
         Files.list(path).toList().forEach { path ->
             val fileName = path.fileName.toString()
             if (fileName.startsWith(IOPlugin.META_FILE_NAME)) {
                 meta(readMetaFile(path))
             } else if (!fileName.startsWith("@")) {
-                runBlocking {
-                    file(this@readDataDirectory, path, formatResolver)
-                }
+                file(path, formatResolver)
             }
         }
     }
 }
 
-@DFExperimental
-public suspend inline fun <reified T : Any> IOPlugin.readDataDirectory(path: Path): DataTree<T> =
-    readDataDirectory(path, formatResolver())
-
 /**
  * Write data tree to existing directory or create a new one using default [java.nio.file.FileSystem] provider
  */
@@ -133,7 +100,7 @@ public suspend inline fun <reified T : Any> IOPlugin.readDataDirectory(path: Pat
 public suspend fun <T : Any> IOPlugin.writeDataDirectory(
     path: Path,
     tree: DataTree<T>,
-    format: IOFormat<T>,
+    format: IOWriter<T>,
     envelopeFormat: EnvelopeFormat? = null,
     metaFormat: MetaFormatFactory? = null,
 ) {
@@ -179,11 +146,9 @@ private suspend fun <T : Any> ZipOutputStream.writeNode(
                 val envelope = treeItem.data.toEnvelope(dataFormat)
                 val entry = ZipEntry(name)
                 putNextEntry(entry)
-                envelopeFormat.run {
-                    asOutput().run {
-                        writeEnvelope(this, envelope)
-                        flush()
-                    }
+                asOutput().run {
+                    envelopeFormat.writeEnvelope(this, envelope)
+                    flush()
                 }
             }
             is DataTreeItem.Node -> {
diff --git a/dataforge-workspace/src/jvmTest/kotlin/space/kscience/dataforge/workspace/FileDataTest.kt b/dataforge-workspace/src/jvmTest/kotlin/space/kscience/dataforge/workspace/FileDataTest.kt
index d1bbb606..a47a648d 100644
--- a/dataforge-workspace/src/jvmTest/kotlin/space/kscience/dataforge/workspace/FileDataTest.kt
+++ b/dataforge-workspace/src/jvmTest/kotlin/space/kscience/dataforge/workspace/FileDataTest.kt
@@ -9,12 +9,8 @@ import space.kscience.dataforge.io.IOFormat
 import space.kscience.dataforge.io.io
 import space.kscience.dataforge.io.readUtf8String
 import space.kscience.dataforge.io.writeUtf8String
-import space.kscience.dataforge.meta.Meta
 import space.kscience.dataforge.misc.DFExperimental
 import java.nio.file.Files
-import java.nio.file.Path
-import kotlin.reflect.KType
-import kotlin.reflect.typeOf
 import kotlin.test.Test
 import kotlin.test.assertEquals
 
@@ -35,8 +31,6 @@ class FileDataTest {
 
     object StringIOFormat : IOFormat<String> {
 
-        override val type: KType = typeOf<String>()
-
         override fun writeObject(output: Output, obj: String) {
             output.writeUtf8String(obj)
         }
@@ -45,17 +39,6 @@ class FileDataTest {
             return input.readUtf8String()
         }
 
-        override fun toMeta(): Meta = Meta {
-            IOFormat.NAME_KEY put "string"
-        }
-
-    }
-
-    object StringFormatResolver : FileFormatResolver<String> {
-        override val type: KType = typeOf<String>()
-
-        override fun invoke(path: Path, meta: Meta): IOFormat<String> = StringIOFormat
-
     }
 
     @Test
@@ -66,7 +49,7 @@ class FileDataTest {
             runBlocking {
                 writeDataDirectory(dir, dataNode, StringIOFormat)
                 println(dir.toUri().toString())
-                val reconstructed = readDataDirectory(dir, StringFormatResolver)
+                val reconstructed = readDataDirectory(dir) { _, _ -> StringIOFormat }
                 assertEquals(dataNode["dir.a"]?.meta, reconstructed["dir.a"]?.meta)
                 assertEquals(dataNode["b"]?.await(), reconstructed["b"]?.await())
             }
@@ -82,7 +65,7 @@ class FileDataTest {
             runBlocking {
                 writeZip(zip, dataNode, StringIOFormat)
                 println(zip.toUri().toString())
-                val reconstructed = readDataDirectory(zip, StringFormatResolver)
+                val reconstructed = readDataDirectory(zip) { _, _ -> StringIOFormat }
                 assertEquals(dataNode["dir.a"]?.meta, reconstructed["dir.a"]?.meta)
                 assertEquals(dataNode["b"]?.await(), reconstructed["b"]?.await())
             }
diff --git a/gradle.properties b/gradle.properties
index 0de6ab36..1aeadb9b 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -4,4 +4,4 @@ kotlin.code.style=official
 
 kotlin.mpp.stability.nowarn=true
 
-toolsVersion=0.11.4-kotlin-1.6.20
+toolsVersion=0.11.5-kotlin-1.6.21