diff --git a/implementations/rust/preserves-schema/src/compiler/mod.rs b/implementations/rust/preserves-schema/src/compiler/mod.rs
index ba3f193..dabb35e 100644
--- a/implementations/rust/preserves-schema/src/compiler/mod.rs
+++ b/implementations/rust/preserves-schema/src/compiler/mod.rs
@@ -151,7 +151,7 @@ pub fn compile(config: &CompilerConfig) -> Result<(), std::io::Error> {
             lines.push(format!("    use {}::support as _support;", &config.support_crate));
             lines.push("    _support::lazy_static! {".to_owned());
             for (value, name) in &m.literals {
-                let bs = preserves::value::PackedWriter::encode(&value).unwrap();
+                let bs = preserves::value::PackedWriter::encode_iovalue(&value).unwrap();
                 lines.push(format!(
                     "        pub static ref {}: {} = /* {:?} */ _support::decode_lit(&vec!{:?}).unwrap();",
                     name,
diff --git a/implementations/rust/preserves-schema/src/support/mod.rs b/implementations/rust/preserves-schema/src/support/mod.rs
index fce6074..1f8066b 100644
--- a/implementations/rust/preserves-schema/src/support/mod.rs
+++ b/implementations/rust/preserves-schema/src/support/mod.rs
@@ -6,7 +6,7 @@ use preserves::value::Embeddable;
 use preserves::value::IOResult;
 use preserves::value::IOValue;
 use preserves::value::NestedValue;
-use preserves::value::NoEmbeddedDomainDecode;
+use preserves::value::NoEmbeddedDomainCodec;
 use preserves::value::Value;
 
 use std::convert::From;
@@ -14,7 +14,7 @@ use std::convert::TryFrom;
 use std::sync::Arc;
 
 pub fn decode_lit<D: Embeddable, N: NestedValue<D>>(bs: &[u8]) -> IOResult<N> {
-    preserves::value::packed::from_bytes(bs, NoEmbeddedDomainDecode)
+    preserves::value::packed::from_bytes(bs, NoEmbeddedDomainCodec)
 }
 
 pub fn decode_embedded<D: Domain>(
diff --git a/implementations/rust/preserves/src/de.rs b/implementations/rust/preserves/src/de.rs
index 40b4117..9faca1d 100644
--- a/implementations/rust/preserves/src/de.rs
+++ b/implementations/rust/preserves/src/de.rs
@@ -4,7 +4,7 @@ use serde::de::{Visitor, SeqAccess, MapAccess, EnumAccess, VariantAccess, Deseri
 use std::borrow::Cow;
 use std::marker::PhantomData;
 
-use super::value::{IOValue, IOValueDomainDecode, PackedReader};
+use super::value::{IOValue, IOValueDomainCodec, PackedReader};
 use super::value::reader::{Reader, IOBinarySource, BytesBinarySource};
 
 pub use super::error::Error;
@@ -21,7 +21,7 @@ pub fn from_bytes<'de, T>(bytes: &'de [u8]) ->
 where
     T: Deserialize<'de>
 {
-    from_reader(&mut PackedReader::new(&mut BytesBinarySource::new(bytes), IOValueDomainDecode))
+    from_reader(&mut PackedReader::new(&mut BytesBinarySource::new(bytes), IOValueDomainCodec))
 }
 
 pub fn from_read<'de, 'r, IOR: std::io::Read, T>(read: &'r mut IOR) ->
@@ -29,7 +29,7 @@ pub fn from_read<'de, 'r, IOR: std::io::Read, T>(read: &'r mut IOR) ->
 where
     T: Deserialize<'de>
 {
-    from_reader(&mut PackedReader::new(&mut IOBinarySource::new(read), IOValueDomainDecode))
+    from_reader(&mut PackedReader::new(&mut IOBinarySource::new(read), IOValueDomainCodec))
 }
 
 pub fn from_reader<'r, 'de, R: Reader<'de, IOValue, IOValue>, T>(read: &'r mut R) ->
diff --git a/implementations/rust/preserves/src/lib.rs b/implementations/rust/preserves/src/lib.rs
index 1b3fc5f..dad9ebc 100644
--- a/implementations/rust/preserves/src/lib.rs
+++ b/implementations/rust/preserves/src/lib.rs
@@ -29,7 +29,7 @@ mod dom {
                                                 Value::Embedded(Dom::One).wrap(),
                                                 Value::from(2).wrap()])
             .wrap();
-        assert_eq!(PackedWriter::encode(&v.copy_via(&mut dom_as_preserves).unwrap()).unwrap(),
+        assert_eq!(PackedWriter::encode_iovalue(&v.copy_via(&mut dom_as_preserves).unwrap()).unwrap(),
                    [0xb5, 0x91, 0xb2, 0x04, 255, 255, 255, 255, 0x92, 0x84]);
     }
 
@@ -38,7 +38,7 @@ mod dom {
                                                 Value::Embedded(Dom::Two).wrap(),
                                                 Value::from(2).wrap()])
             .wrap();
-        assert_eq!(PackedWriter::encode(&v.copy_via(&mut dom_as_preserves).unwrap()).unwrap(),
+        assert_eq!(PackedWriter::encode_iovalue(&v.copy_via(&mut dom_as_preserves).unwrap()).unwrap(),
                    [0xb5, 0x91, 0xb3, 0x08, 68, 111, 109, 58, 58, 84, 119, 111, 0x92, 0x84]);
     }
 }
@@ -465,7 +465,7 @@ mod serde_tests {
         println!("== y: {:#?}", &y);
         assert_eq!(v, y);
 
-        let v_bytes_1 = PackedWriter::encode(&w).unwrap();
+        let v_bytes_1 = PackedWriter::encode_iovalue(&w).unwrap();
         println!("== w bytes = {:?}", v_bytes_1);
         assert_eq!(expected_bytes, v_bytes_1);
 
diff --git a/implementations/rust/preserves/src/ser.rs b/implementations/rust/preserves/src/ser.rs
index 696d310..15d95c2 100644
--- a/implementations/rust/preserves/src/ser.rs
+++ b/implementations/rust/preserves/src/ser.rs
@@ -1,4 +1,5 @@
 use serde::Serialize;
+use super::value::IOValueDomainCodec;
 use super::value::writer::{Writer, CompoundWriter};
 
 pub use super::error::Error;
@@ -153,7 +154,7 @@ impl<'a, 'w, W: Writer> serde::Serializer for &'a mut Serializer<'w, W> {
         Result<Self::Ok> where T: Serialize
     {
         match super::value::magic::receive_output_value(name, value) {
-            Some(v) => Ok(self.write.write(&v)?),
+            Some(v) => Ok(self.write.write(&mut IOValueDomainCodec, &v)?),
             None => {
                 // TODO: This is apparently discouraged, and we should apparently just serialize `value`?
                 let mut c = self.write.start_record(Some(1))?;
diff --git a/implementations/rust/preserves/src/value/domain.rs b/implementations/rust/preserves/src/value/domain.rs
index 6500356..cf4a0a2 100644
--- a/implementations/rust/preserves/src/value/domain.rs
+++ b/implementations/rust/preserves/src/value/domain.rs
@@ -3,6 +3,7 @@ use super::Embeddable;
 use super::IOResult;
 use super::IOValue;
 use super::Reader;
+use super::Writer;
 use super::packed::PackedReader;
 
 pub trait DomainDecode<D: Embeddable> {
@@ -13,21 +14,39 @@ pub trait DomainDecode<D: Embeddable> {
     ) -> IOResult<D>;
 }
 
-pub struct IOValueDomainDecode;
+pub trait DomainEncode<D: Embeddable> {
+    fn encode_embedded<W: Writer>(
+        &mut self,
+        w: &mut W,
+        d: &D,
+    ) -> IOResult<()>;
+}
 
-impl DomainDecode<IOValue> for IOValueDomainDecode {
+pub struct IOValueDomainCodec;
+
+impl DomainDecode<IOValue> for IOValueDomainCodec {
     fn decode_embedded<'de, 'src, S: BinarySource<'de>>(
         &mut self,
         src: &'src mut S,
         read_annotations: bool,
     ) -> IOResult<IOValue> {
-        PackedReader::new(src, IOValueDomainDecode).demand_next(read_annotations)
+        PackedReader::new(src, IOValueDomainCodec).demand_next(read_annotations)
     }
 }
 
-pub struct NoEmbeddedDomainDecode;
+impl DomainEncode<IOValue> for IOValueDomainCodec {
+    fn encode_embedded<W: Writer>(
+        &mut self,
+        w: &mut W,
+        d: &IOValue,
+    ) -> IOResult<()> {
+        w.write(self, d)
+    }
+}
 
-impl<D: Embeddable> DomainDecode<D> for NoEmbeddedDomainDecode {
+pub struct NoEmbeddedDomainCodec;
+
+impl<D: Embeddable> DomainDecode<D> for NoEmbeddedDomainCodec {
     fn decode_embedded<'de, 'src, S: BinarySource<'de>>(
         &mut self,
         _src: &'src mut S,
@@ -36,3 +55,13 @@ impl<D: Embeddable> DomainDecode<D> for NoEmbeddedDomainDecode {
         Err(std::io::Error::new(std::io::ErrorKind::Unsupported, "Embedded values not supported here"))
     }
 }
+
+impl<D: Embeddable> DomainEncode<D> for NoEmbeddedDomainCodec {
+    fn encode_embedded<W: Writer>(
+        &mut self,
+        _w: &mut W,
+        _d: &D,
+    ) -> IOResult<()> {
+        Err(std::io::Error::new(std::io::ErrorKind::Unsupported, "Embedded values not supported here"))
+    }
+}
diff --git a/implementations/rust/preserves/src/value/mod.rs b/implementations/rust/preserves/src/value/mod.rs
index cbf2f35..a3e9abd 100644
--- a/implementations/rust/preserves/src/value/mod.rs
+++ b/implementations/rust/preserves/src/value/mod.rs
@@ -11,8 +11,9 @@ pub mod writer;
 pub use de::Deserializer;
 pub use de::from_value;
 pub use domain::DomainDecode;
-pub use domain::IOValueDomainDecode;
-pub use domain::NoEmbeddedDomainDecode;
+pub use domain::DomainEncode;
+pub use domain::IOValueDomainCodec;
+pub use domain::NoEmbeddedDomainCodec;
 pub use packed::PackedReader;
 pub use packed::PackedWriter;
 pub use reader::BinarySource;
diff --git a/implementations/rust/preserves/src/value/packed/mod.rs b/implementations/rust/preserves/src/value/packed/mod.rs
index e0368fd..7c2e47a 100644
--- a/implementations/rust/preserves/src/value/packed/mod.rs
+++ b/implementations/rust/preserves/src/value/packed/mod.rs
@@ -5,7 +5,7 @@ pub mod writer;
 pub use reader::PackedReader;
 pub use writer::PackedWriter;
 
-use super::{BinarySource, DomainDecode, Embeddable, IOResult, IOValue, IOValueDomainDecode, NestedValue, Reader};
+use super::{BinarySource, DomainDecode, Embeddable, IOResult, IOValue, IOValueDomainCodec, NestedValue, Reader};
 
 pub fn from_bytes<D: Embeddable, N: NestedValue<D>, Dec: DomainDecode<D>>(
     bs: &[u8],
@@ -15,7 +15,7 @@ pub fn from_bytes<D: Embeddable, N: NestedValue<D>, Dec: DomainDecode<D>>(
 }
 
 pub fn iovalue_from_bytes(bs: &[u8]) -> IOResult<IOValue> {
-    from_bytes(bs, IOValueDomainDecode)
+    from_bytes(bs, IOValueDomainCodec)
 }
 
 pub fn annotated_from_bytes<D: Embeddable, N: NestedValue<D>, Dec: DomainDecode<D>>(
@@ -26,5 +26,5 @@ pub fn annotated_from_bytes<D: Embeddable, N: NestedValue<D>, Dec: DomainDecode<
 }
 
 pub fn annotated_iovalue_from_bytes(bs: &[u8]) -> IOResult<IOValue> {
-    annotated_from_bytes(bs, IOValueDomainDecode)
+    annotated_from_bytes(bs, IOValueDomainCodec)
 }
diff --git a/implementations/rust/preserves/src/value/packed/writer.rs b/implementations/rust/preserves/src/value/packed/writer.rs
index efe168b..b583874 100644
--- a/implementations/rust/preserves/src/value/packed/writer.rs
+++ b/implementations/rust/preserves/src/value/packed/writer.rs
@@ -4,9 +4,14 @@ use std::convert::TryInto;
 use std::mem;
 use std::ops::{Deref, DerefMut};
 use super::constants::Tag;
+use super::super::DomainEncode;
+use super::super::Embeddable;
 use super::super::IOValue;
+use super::super::IOValueDomainCodec;
+use super::super::IOResult;
+use super::super::NestedValue;
 
-use super::super::writer::{Writer, AnnotationWriter, CompoundWriter, Result, varint};
+use super::super::writer::{Writer, AnnotationWriter, CompoundWriter, varint};
 
 pub enum Suspendable<T> {
     Active(T),
@@ -70,12 +75,19 @@ impl<T> DerefMut for Suspendable<T> {
 pub struct PackedWriter<W: std::io::Write>(Suspendable<W>);
 
 impl PackedWriter<Vec<u8>> {
-    pub fn encode(v: &IOValue) -> std::io::Result<Vec<u8>> {
+    pub fn encode<D: Embeddable, N: NestedValue<D>, Enc: DomainEncode<D>>(
+        enc: &mut Enc,
+        v: &N,
+    ) -> IOResult<Vec<u8>> {
         let mut buf: Vec<u8> = Vec::new();
         let w = &mut PackedWriter::new(&mut buf);
-        w.write(v)?;
+        w.write(enc, v)?;
         Ok(buf)
     }
+
+    pub fn encode_iovalue(v: &IOValue) -> std::io::Result<Vec<u8>> {
+        Self::encode(&mut IOValueDomainCodec, v)
+    }
 }
 
 impl<W: std::io::Write> PackedWriter<W> {
@@ -87,18 +99,18 @@ impl<W: std::io::Write> PackedWriter<W> {
         self.0.deref_mut()
     }
 
-    pub fn write_byte(&mut self, b: u8) -> Result<()> {
+    pub fn write_byte(&mut self, b: u8) -> IOResult<()> {
         self.w().write_all(&[b])
     }
 
-    pub fn write_medium_integer(&mut self, bs: &[u8]) -> Result<()> {
+    pub fn write_medium_integer(&mut self, bs: &[u8]) -> IOResult<()> {
         let count: u8 = bs.len().try_into().unwrap();
         if !(1..=16).contains(&count) { panic!("Invalid medium_integer count: {}", count) }
         self.write_byte(Tag::MediumInteger(count).into())?;
         self.w().write_all(bs)
     }
 
-    pub fn write_atom(&mut self, tag: Tag, bs: &[u8]) -> Result<()> {
+    pub fn write_atom(&mut self, tag: Tag, bs: &[u8]) -> IOResult<()> {
         self.write_byte(tag.into())?;
         varint(&mut self.w(), bs.len().try_into().unwrap())?;
         self.w().write_all(bs)
@@ -140,7 +152,7 @@ impl BinaryOrderWriter {
         self.0.last_mut().unwrap()
     }
 
-    fn finish<W: WriteWriter>(mut self, w: &mut W) -> Result<()> {
+    fn finish<W: WriteWriter>(mut self, w: &mut W) -> IOResult<()> {
         if !self.buffer().is_empty() { panic!("Missing final delimit()"); }
         self.items_mut().pop();
         self.items_mut().sort();
@@ -153,51 +165,51 @@ impl BinaryOrderWriter {
 }
 
 pub trait WriteWriter: Writer {
-    fn write_raw_bytes(&mut self, v: &[u8]) -> Result<()>;
-    fn write_tag(&mut self, tag: Tag) -> Result<()> {
+    fn write_raw_bytes(&mut self, v: &[u8]) -> IOResult<()>;
+    fn write_tag(&mut self, tag: Tag) -> IOResult<()> {
         self.write_raw_bytes(&[tag.into()])
     }
 }
 
 impl<W: std::io::Write> WriteWriter for PackedWriter<W> {
-    fn write_raw_bytes(&mut self, v: &[u8]) -> Result<()> {
+    fn write_raw_bytes(&mut self, v: &[u8]) -> IOResult<()> {
         self.w().write_all(v)
     }
 }
 
 impl WriteWriter for BinaryOrderWriter {
-    fn write_raw_bytes(&mut self, v: &[u8]) -> Result<()> {
+    fn write_raw_bytes(&mut self, v: &[u8]) -> IOResult<()> {
         use std::io::Write;
         self.buffer().write_all(v)
     }
 }
 
 impl<T: WriteWriter> AnnotationWriter for T {
-    fn start_annotation(&mut self) -> Result<()> {
+    fn start_annotation(&mut self) -> IOResult<()> {
         Ok(self.write_tag(Tag::Annotation)?)
     }
 
-    fn start_value(&mut self) -> Result<()> {
+    fn start_value(&mut self) -> IOResult<()> {
         Ok(())
     }
 }
 
 impl<W: std::io::Write> CompoundWriter for PackedWriter<W> {
-    fn extend(&mut self) -> Result<()> {
+    fn extend(&mut self) -> IOResult<()> {
         Ok(())
     }
 
-    fn delimit(&mut self) -> Result<()> {
+    fn delimit(&mut self) -> IOResult<()> {
         Ok(())
     }
 }
 
 impl CompoundWriter for BinaryOrderWriter {
-    fn extend(&mut self) -> Result<()> {
+    fn extend(&mut self) -> IOResult<()> {
         Ok(())
     }
 
-    fn delimit(&mut self) -> Result<()> {
+    fn delimit(&mut self) -> IOResult<()> {
         self.items_mut().push(vec![]);
         Ok(())
     }
@@ -216,67 +228,67 @@ impl Writer for BinaryOrderWriter {
     type SetWriter = BinaryOrderWriter;
     type EmbeddedWriter = PackedWriter<Vec<u8>>;
 
-    binary_order_writer_method!(mut align(natural_chunksize: u64) -> Result<()>);
+    binary_order_writer_method!(mut align(natural_chunksize: u64) -> IOResult<()>);
 
-    fn start_annotations(&mut self) -> Result<Self::AnnWriter> {
+    fn start_annotations(&mut self) -> IOResult<Self::AnnWriter> {
         Ok(self.pop())
     }
-    fn end_annotations(&mut self, ann: Self::AnnWriter) -> Result<()> {
+    fn end_annotations(&mut self, ann: Self::AnnWriter) -> IOResult<()> {
         self.push(ann);
         Ok(())
     }
 
-    binary_order_writer_method!(mut write_bool(v: bool) -> Result<()>);
+    binary_order_writer_method!(mut write_bool(v: bool) -> IOResult<()>);
 
-    binary_order_writer_method!(mut write_f32(v: f32) -> Result<()>);
-    binary_order_writer_method!(mut write_f64(v: f64) -> Result<()>);
+    binary_order_writer_method!(mut write_f32(v: f32) -> IOResult<()>);
+    binary_order_writer_method!(mut write_f64(v: f64) -> IOResult<()>);
 
-    binary_order_writer_method!(mut write_i8(v: i8) -> Result<()>);
-    binary_order_writer_method!(mut write_u8(v: u8) -> Result<()>);
-    binary_order_writer_method!(mut write_i16(v: i16) -> Result<()>);
-    binary_order_writer_method!(mut write_u16(v: u16) -> Result<()>);
-    binary_order_writer_method!(mut write_i32(v: i32) -> Result<()>);
-    binary_order_writer_method!(mut write_u32(v: u32) -> Result<()>);
-    binary_order_writer_method!(mut write_i64(v: i64) -> Result<()>);
-    binary_order_writer_method!(mut write_u64(v: u64) -> Result<()>);
-    binary_order_writer_method!(mut write_i128(v: i128) -> Result<()>);
-    binary_order_writer_method!(mut write_u128(v: u128) -> Result<()>);
-    binary_order_writer_method!(mut write_int(v: &BigInt) -> Result<()>);
+    binary_order_writer_method!(mut write_i8(v: i8) -> IOResult<()>);
+    binary_order_writer_method!(mut write_u8(v: u8) -> IOResult<()>);
+    binary_order_writer_method!(mut write_i16(v: i16) -> IOResult<()>);
+    binary_order_writer_method!(mut write_u16(v: u16) -> IOResult<()>);
+    binary_order_writer_method!(mut write_i32(v: i32) -> IOResult<()>);
+    binary_order_writer_method!(mut write_u32(v: u32) -> IOResult<()>);
+    binary_order_writer_method!(mut write_i64(v: i64) -> IOResult<()>);
+    binary_order_writer_method!(mut write_u64(v: u64) -> IOResult<()>);
+    binary_order_writer_method!(mut write_i128(v: i128) -> IOResult<()>);
+    binary_order_writer_method!(mut write_u128(v: u128) -> IOResult<()>);
+    binary_order_writer_method!(mut write_int(v: &BigInt) -> IOResult<()>);
 
-    binary_order_writer_method!(mut write_string(v: &str) -> Result<()>);
-    binary_order_writer_method!(mut write_bytes(v: &[u8]) -> Result<()>);
-    binary_order_writer_method!(mut write_symbol(v: &str) -> Result<()>);
+    binary_order_writer_method!(mut write_string(v: &str) -> IOResult<()>);
+    binary_order_writer_method!(mut write_bytes(v: &[u8]) -> IOResult<()>);
+    binary_order_writer_method!(mut write_symbol(v: &str) -> IOResult<()>);
 
-    fn start_record(&mut self, _field_count: Option<usize>) -> Result<Self::SeqWriter> {
+    fn start_record(&mut self, _field_count: Option<usize>) -> IOResult<Self::SeqWriter> {
         self.write_tag(Tag::Record)?;
         Ok(self.pop())
     }
-    fn start_sequence(&mut self, _item_count: Option<usize>) -> Result<Self::SeqWriter> {
+    fn start_sequence(&mut self, _item_count: Option<usize>) -> IOResult<Self::SeqWriter> {
         self.write_tag(Tag::Sequence)?;
         Ok(self.pop())
     }
-    fn end_seq(&mut self, seq: Self::SeqWriter) -> Result<()> {
+    fn end_seq(&mut self, seq: Self::SeqWriter) -> IOResult<()> {
         self.push(seq);
         self.write_tag(Tag::End)
     }
 
-    fn start_set(&mut self, _item_count: Option<usize>) -> Result<Self::SetWriter> {
+    fn start_set(&mut self, _item_count: Option<usize>) -> IOResult<Self::SetWriter> {
         self.write_tag(Tag::Set)?;
         Ok(BinaryOrderWriter::new())
     }
-    fn start_dictionary(&mut self, _entry_count: Option<usize>) -> Result<Self::SetWriter> {
+    fn start_dictionary(&mut self, _entry_count: Option<usize>) -> IOResult<Self::SetWriter> {
         self.write_tag(Tag::Dictionary)?;
         Ok(BinaryOrderWriter::new())
     }
-    fn end_set(&mut self, set: Self::SetWriter) -> Result<()> {
+    fn end_set(&mut self, set: Self::SetWriter) -> IOResult<()> {
         set.finish(self)
     }
 
-    fn start_embedded(&mut self) -> Result<Self::EmbeddedWriter> {
+    fn start_embedded(&mut self) -> IOResult<Self::EmbeddedWriter> {
         self.write_tag(Tag::Embedded)?;
         Ok(self.pop())
     }
-    fn end_embedded(&mut self, ptr: Self::EmbeddedWriter) -> Result<()> {
+    fn end_embedded(&mut self, ptr: Self::EmbeddedWriter) -> IOResult<()> {
         self.push(ptr);
         Ok(())
     }
@@ -296,54 +308,54 @@ impl<W: std::io::Write> Writer for PackedWriter<W>
     type SetWriter = BinaryOrderWriter;
     type EmbeddedWriter = Self;
 
-    fn start_annotations(&mut self) -> Result<Self::AnnWriter> {
+    fn start_annotations(&mut self) -> IOResult<Self::AnnWriter> {
         Ok(self.suspend())
     }
 
-    fn end_annotations(&mut self, ann: Self::AnnWriter) -> Result<()> {
+    fn end_annotations(&mut self, ann: Self::AnnWriter) -> IOResult<()> {
         self.resume(ann);
         Ok(())
     }
 
-    fn align(&mut self, _natural_chunksize: u64) -> Result<()> {
+    fn align(&mut self, _natural_chunksize: u64) -> IOResult<()> {
         Ok(())
     }
 
-    fn write_bool(&mut self, v: bool) -> Result<()> {
+    fn write_bool(&mut self, v: bool) -> IOResult<()> {
         self.write_tag(if v { Tag::True } else { Tag::False })
     }
 
-    fn write_f32(&mut self, v: f32) -> Result<()> {
+    fn write_f32(&mut self, v: f32) -> IOResult<()> {
         self.write_tag(Tag::Float)?;
         self.write_raw_bytes(&u32::to_be_bytes(f32::to_bits(v)))
     }
 
-    fn write_f64(&mut self, v: f64) -> Result<()> {
+    fn write_f64(&mut self, v: f64) -> IOResult<()> {
         self.write_tag(Tag::Double)?;
         self.write_raw_bytes(&u64::to_be_bytes(f64::to_bits(v)))
     }
 
-    fn write_i8(&mut self, v: i8) -> Result<()> {
+    fn write_i8(&mut self, v: i8) -> IOResult<()> {
         if v >= -3 && v <= 12 { return self.write_tag(Tag::SmallInteger(v)) }
         self.write_medium_integer(&[v as u8])
     }
 
-    fn write_u8(&mut self, v: u8) -> Result<()> {
+    fn write_u8(&mut self, v: u8) -> IOResult<()> {
         if let Ok(w) = v.try_into() { return self.write_i8(w) }
         self.write_medium_integer(&[0, v])
     }
 
-    fn write_i16(&mut self, v: i16) -> Result<()> {
+    fn write_i16(&mut self, v: i16) -> IOResult<()> {
         if let Ok(w) = v.try_into() { return self.write_i8(w) }
         self.write_medium_integer(&[(v >> 8) as u8, (v & 255) as u8])
     }
 
-    fn write_u16(&mut self, v: u16) -> Result<()> {
+    fn write_u16(&mut self, v: u16) -> IOResult<()> {
         if let Ok(w) = v.try_into() { return self.write_i16(w) }
         self.write_medium_integer(&[0, (v >> 8) as u8, (v & 255) as u8])
     }
 
-    fn write_i32(&mut self, v: i32) -> Result<()> {
+    fn write_i32(&mut self, v: i32) -> IOResult<()> {
         if let Ok(w) = v.try_into() { return self.write_i16(w) }
         if fits_in_bytes!(v, 3) {
             return self.write_medium_integer(&[(v >> 16) as u8,
@@ -356,7 +368,7 @@ impl<W: std::io::Write> Writer for PackedWriter<W>
                                     (v & 255) as u8])
     }
 
-    fn write_u32(&mut self, v: u32) -> Result<()> {
+    fn write_u32(&mut self, v: u32) -> IOResult<()> {
         if let Ok(w) = v.try_into() { return self.write_i32(w) }
         self.write_medium_integer(&[0,
                                     (v >> 24) as u8,
@@ -365,7 +377,7 @@ impl<W: std::io::Write> Writer for PackedWriter<W>
                                     (v & 255) as u8])
     }
 
-    fn write_i64(&mut self, v: i64) -> Result<()> {
+    fn write_i64(&mut self, v: i64) -> IOResult<()> {
         if let Ok(w) = v.try_into() { return self.write_i32(w) }
         if fits_in_bytes!(v, 5) {
             return self.write_medium_integer(&[(v >> 32) as u8,
@@ -401,7 +413,7 @@ impl<W: std::io::Write> Writer for PackedWriter<W>
                                     (v & 255) as u8])
     }
 
-    fn write_u64(&mut self, v: u64) -> Result<()> {
+    fn write_u64(&mut self, v: u64) -> IOResult<()> {
         if let Ok(w) = v.try_into() { return self.write_i64(w) }
         self.write_medium_integer(&[0,
                                     (v >> 56) as u8,
@@ -414,7 +426,7 @@ impl<W: std::io::Write> Writer for PackedWriter<W>
                                     (v & 255) as u8])
     }
 
-    fn write_i128(&mut self, v: i128) -> Result<()> {
+    fn write_i128(&mut self, v: i128) -> IOResult<()> {
         if let Ok(w) = v.try_into() { return self.write_i64(w) }
         let bs: [u8; 16] = v.to_be_bytes();
         if fits_in_bytes!(v, 9)  { return self.write_medium_integer(&bs[7..]); }
@@ -427,7 +439,7 @@ impl<W: std::io::Write> Writer for PackedWriter<W>
         self.write_medium_integer(&bs)
     }
 
-    fn write_u128(&mut self, v: u128) -> Result<()> {
+    fn write_u128(&mut self, v: u128) -> IOResult<()> {
         if let Ok(w) = v.try_into() { return self.write_i128(w) }
         let bs: [u8; 16] = v.to_be_bytes();
         self.write_tag(Tag::SignedInteger)?;
@@ -436,7 +448,7 @@ impl<W: std::io::Write> Writer for PackedWriter<W>
         self.write_raw_bytes(&bs)
     }
 
-    fn write_int(&mut self, v: &BigInt) -> Result<()> {
+    fn write_int(&mut self, v: &BigInt) -> IOResult<()> {
         match v.to_i8() {
             Some(n) => self.write_i8(n),
             None => {
@@ -448,53 +460,53 @@ impl<W: std::io::Write> Writer for PackedWriter<W>
         }
     }
 
-    fn write_string(&mut self, v: &str) -> Result<()> {
+    fn write_string(&mut self, v: &str) -> IOResult<()> {
         self.write_atom(Tag::String, v.as_bytes())
     }
 
-    fn write_bytes(&mut self, v: &[u8]) -> Result<()> {
+    fn write_bytes(&mut self, v: &[u8]) -> IOResult<()> {
         self.write_atom(Tag::ByteString, v)
     }
 
-    fn write_symbol(&mut self, v: &str) -> Result<()> {
+    fn write_symbol(&mut self, v: &str) -> IOResult<()> {
         self.write_atom(Tag::Symbol, v.as_bytes())
     }
 
-    fn start_record(&mut self, _field_count: Option<usize>) -> Result<Self::SeqWriter> {
+    fn start_record(&mut self, _field_count: Option<usize>) -> IOResult<Self::SeqWriter> {
         self.write_tag(Tag::Record)?;
         Ok(self.suspend())
     }
 
-    fn start_sequence(&mut self, _item_count: Option<usize>) -> Result<Self::SeqWriter> {
+    fn start_sequence(&mut self, _item_count: Option<usize>) -> IOResult<Self::SeqWriter> {
         self.write_tag(Tag::Sequence)?;
         Ok(self.suspend())
     }
 
-    fn end_seq(&mut self, seq: Self::SeqWriter) -> Result<()> {
+    fn end_seq(&mut self, seq: Self::SeqWriter) -> IOResult<()> {
         self.resume(seq);
         self.write_tag(Tag::End)
     }
 
-    fn start_set(&mut self, _item_count: Option<usize>) -> Result<Self::SetWriter> {
+    fn start_set(&mut self, _item_count: Option<usize>) -> IOResult<Self::SetWriter> {
         self.write_tag(Tag::Set)?;
         Ok(BinaryOrderWriter::new())
     }
 
-    fn start_dictionary(&mut self, _entry_count: Option<usize>) -> Result<Self::SetWriter> {
+    fn start_dictionary(&mut self, _entry_count: Option<usize>) -> IOResult<Self::SetWriter> {
         self.write_tag(Tag::Dictionary)?;
         Ok(BinaryOrderWriter::new())
     }
 
-    fn end_set(&mut self, set: Self::SetWriter) -> Result<()> {
+    fn end_set(&mut self, set: Self::SetWriter) -> IOResult<()> {
         set.finish(self)
     }
 
-    fn start_embedded(&mut self) -> Result<Self::EmbeddedWriter> {
+    fn start_embedded(&mut self) -> IOResult<Self::EmbeddedWriter> {
         self.write_tag(Tag::Embedded)?;
         Ok(self.suspend())
     }
 
-    fn end_embedded(&mut self, ann: Self::EmbeddedWriter) -> Result<()> {
+    fn end_embedded(&mut self, ann: Self::EmbeddedWriter) -> IOResult<()> {
         self.resume(ann);
         Ok(())
     }
diff --git a/implementations/rust/preserves/src/value/reader.rs b/implementations/rust/preserves/src/value/reader.rs
index 553e5bf..088f164 100644
--- a/implementations/rust/preserves/src/value/reader.rs
+++ b/implementations/rust/preserves/src/value/reader.rs
@@ -4,7 +4,7 @@ use std::borrow::Cow;
 use std::io::Read;
 use std::marker::PhantomData;
 
-use super::{DomainDecode, Embeddable, IOResult, IOValue, IOValueDomainDecode, NestedValue};
+use super::{DomainDecode, Embeddable, IOResult, IOValue, IOValueDomainCodec, NestedValue};
 
 pub type ReaderResult<T> = std::result::Result<T, error::Error>;
 
@@ -173,9 +173,9 @@ pub trait BinarySource<'de>: Sized {
     }
 
     fn packed_iovalues(&mut self) ->
-        super::PackedReader<'de, '_, IOValue, IOValue, IOValueDomainDecode, Self>
+        super::PackedReader<'de, '_, IOValue, IOValue, IOValueDomainCodec, Self>
     {
-        self.packed(IOValueDomainDecode)
+        self.packed(IOValueDomainCodec)
     }
 }
 
diff --git a/implementations/rust/preserves/src/value/writer.rs b/implementations/rust/preserves/src/value/writer.rs
index 41421f5..d90186b 100644
--- a/implementations/rust/preserves/src/value/writer.rs
+++ b/implementations/rust/preserves/src/value/writer.rs
@@ -1,18 +1,17 @@
 use num::bigint::BigInt;
-use std::io::Error;
+use super::DomainEncode;
+use super::IOResult;
 use super::signed_integer::SignedIntegerRepr;
-use super::repr::{Value, NestedValue, IOValue, UnwrappedIOValue, Float, Double};
-
-pub type Result<T> = std::result::Result<T, Error>;
+use super::repr::{Embeddable, Value, NestedValue, Float, Double};
 
 pub trait AnnotationWriter: Writer {
-    fn start_annotation(&mut self) -> Result<()>;
-    fn start_value(&mut self) -> Result<()>;
+    fn start_annotation(&mut self) -> IOResult<()>;
+    fn start_value(&mut self) -> IOResult<()>;
 }
 
 pub trait CompoundWriter: Writer {
-    fn extend(&mut self) -> Result<()>;
-    fn delimit(&mut self) -> Result<()>;
+    fn extend(&mut self) -> IOResult<()>;
+    fn delimit(&mut self) -> IOResult<()>;
 }
 
 pub trait Writer: Sized {
@@ -21,65 +20,73 @@ pub trait Writer: Sized {
     type SetWriter: CompoundWriter;
     type EmbeddedWriter: Writer;
 
-    fn align(&mut self, natural_chunksize: u64) -> Result<()>;
+    fn align(&mut self, natural_chunksize: u64) -> IOResult<()>;
 
-    fn start_annotations(&mut self) -> Result<Self::AnnWriter>;
-    fn end_annotations(&mut self, ann: Self::AnnWriter) -> Result<()>;
+    fn start_annotations(&mut self) -> IOResult<Self::AnnWriter>;
+    fn end_annotations(&mut self, ann: Self::AnnWriter) -> IOResult<()>;
 
-    fn write_bool(&mut self, v: bool) -> Result<()>;
+    fn write_bool(&mut self, v: bool) -> IOResult<()>;
 
-    fn write_f32(&mut self, v: f32) -> Result<()>;
-    fn write_f64(&mut self, v: f64) -> Result<()>;
+    fn write_f32(&mut self, v: f32) -> IOResult<()>;
+    fn write_f64(&mut self, v: f64) -> IOResult<()>;
 
-    fn write_i8(&mut self, v: i8) -> Result<()>;
-    fn write_u8(&mut self, v: u8) -> Result<()>;
-    fn write_i16(&mut self, v: i16) -> Result<()>;
-    fn write_u16(&mut self, v: u16) -> Result<()>;
-    fn write_i32(&mut self, v: i32) -> Result<()>;
-    fn write_u32(&mut self, v: u32) -> Result<()>;
-    fn write_i64(&mut self, v: i64) -> Result<()>;
-    fn write_u64(&mut self, v: u64) -> Result<()>;
-    fn write_i128(&mut self, v: i128) -> Result<()>;
-    fn write_u128(&mut self, v: u128) -> Result<()>;
-    fn write_int(&mut self, v: &BigInt) -> Result<()>;
+    fn write_i8(&mut self, v: i8) -> IOResult<()>;
+    fn write_u8(&mut self, v: u8) -> IOResult<()>;
+    fn write_i16(&mut self, v: i16) -> IOResult<()>;
+    fn write_u16(&mut self, v: u16) -> IOResult<()>;
+    fn write_i32(&mut self, v: i32) -> IOResult<()>;
+    fn write_u32(&mut self, v: u32) -> IOResult<()>;
+    fn write_i64(&mut self, v: i64) -> IOResult<()>;
+    fn write_u64(&mut self, v: u64) -> IOResult<()>;
+    fn write_i128(&mut self, v: i128) -> IOResult<()>;
+    fn write_u128(&mut self, v: u128) -> IOResult<()>;
+    fn write_int(&mut self, v: &BigInt) -> IOResult<()>;
 
-    fn write_string(&mut self, v: &str) -> Result<()>;
-    fn write_bytes(&mut self, v: &[u8]) -> Result<()>;
-    fn write_symbol(&mut self, v: &str) -> Result<()>;
+    fn write_string(&mut self, v: &str) -> IOResult<()>;
+    fn write_bytes(&mut self, v: &[u8]) -> IOResult<()>;
+    fn write_symbol(&mut self, v: &str) -> IOResult<()>;
 
-    fn start_record(&mut self, field_count: Option<usize>) -> Result<Self::SeqWriter>;
-    fn start_sequence(&mut self, item_count: Option<usize>) -> Result<Self::SeqWriter>;
-    fn end_seq(&mut self, seq: Self::SeqWriter) -> Result<()>;
+    fn start_record(&mut self, field_count: Option<usize>) -> IOResult<Self::SeqWriter>;
+    fn start_sequence(&mut self, item_count: Option<usize>) -> IOResult<Self::SeqWriter>;
+    fn end_seq(&mut self, seq: Self::SeqWriter) -> IOResult<()>;
 
-    fn start_set(&mut self, item_count: Option<usize>) -> Result<Self::SetWriter>;
-    fn start_dictionary(&mut self, entry_count: Option<usize>) -> Result<Self::SetWriter>;
-    fn end_set(&mut self, set: Self::SetWriter) -> Result<()>;
+    fn start_set(&mut self, item_count: Option<usize>) -> IOResult<Self::SetWriter>;
+    fn start_dictionary(&mut self, entry_count: Option<usize>) -> IOResult<Self::SetWriter>;
+    fn end_set(&mut self, set: Self::SetWriter) -> IOResult<()>;
 
-    fn start_embedded(&mut self) -> Result<Self::EmbeddedWriter>;
-    fn end_embedded(&mut self, ptr: Self::EmbeddedWriter) -> Result<()>;
+    fn start_embedded(&mut self) -> IOResult<Self::EmbeddedWriter>;
+    fn end_embedded(&mut self, ptr: Self::EmbeddedWriter) -> IOResult<()>;
 
     //---------------------------------------------------------------------------
 
-    fn write(&mut self, v: &IOValue) -> Result<()> {
+    fn write<D: Embeddable, N: NestedValue<D>, Enc: DomainEncode<D>>(
+        &mut self,
+        enc: &mut Enc,
+        v: &N,
+    ) -> IOResult<()> {
         match v.annotations().maybe_slice() {
             None => {
-                self.write_value(v.value())?;
+                self.write_value(enc, v.value())?;
             }
             Some(anns) => {
                 let mut a = self.start_annotations()?;
                 for ann in anns {
                     a.start_annotation()?;
-                    a.write(ann)?;
+                    a.write(enc, ann)?;
                 }
                 a.start_value()?;
-                a.write_value(v.value())?;
+                a.write_value(enc, v.value())?;
                 self.end_annotations(a)?;
             }
         }
         Ok(())
     }
 
-    fn write_value(&mut self, v: &UnwrappedIOValue) -> Result<()> {
+    fn write_value<D: Embeddable, N: NestedValue<D>, Enc: DomainEncode<D>>(
+        &mut self,
+        enc: &mut Enc,
+        v: &Value<N, D>,
+    ) -> IOResult<()> {
         match v {
             Value::Boolean(b) => self.write_bool(*b),
             Value::Float(Float(f)) => self.write_f32(*f),
@@ -95,11 +102,11 @@ pub trait Writer: Sized {
             Value::Record(r) => {
                 let mut c = self.start_record(Some(r.arity()))?;
                 c.extend()?;
-                c.write(r.label())?;
+                c.write(enc, r.label())?;
                 c.delimit()?;
                 for f in r.fields() {
                     c.extend()?;
-                    c.write(f)?;
+                    c.write(enc, f)?;
                     c.delimit()?;
                 }
                 self.end_seq(c)
@@ -108,7 +115,7 @@ pub trait Writer: Sized {
                 let mut c = self.start_sequence(Some(vs.len()))?;
                 for v in vs {
                     c.extend()?;
-                    c.write(v)?;
+                    c.write(enc, v)?;
                     c.delimit()?;
                 }
                 self.end_seq(c)
@@ -117,7 +124,7 @@ pub trait Writer: Sized {
                 let mut c = self.start_set(Some(vs.len()))?;
                 for v in vs {
                     c.extend()?;
-                    c.write(v)?;
+                    c.write(enc, v)?;
                     c.delimit()?;
                 }
                 self.end_set(c)
@@ -126,22 +133,22 @@ pub trait Writer: Sized {
                 let mut c = self.start_dictionary(Some(vs.len()))?;
                 for (k, v) in vs {
                     c.extend()?;
-                    c.write(k)?;
-                    c.write(v)?;
+                    c.write(enc, k)?;
+                    c.write(enc, v)?;
                     c.delimit()?;
                 }
                 self.end_set(c)
             }
             Value::Embedded(d) => {
                 let mut c = self.start_embedded()?;
-                c.write(&d)?;
+                enc.encode_embedded(&mut c, d)?;
                 self.end_embedded(c)
             }
         }
     }
 }
 
-pub fn varint<W: std::io::Write>(w: &mut W, mut v: u64) -> Result<usize> {
+pub fn varint<W: std::io::Write>(w: &mut W, mut v: u64) -> IOResult<usize> {
     let mut byte_count = 0;
     loop {
         byte_count += 1;
diff --git a/implementations/rust/preserves/tests/samples_tests.rs b/implementations/rust/preserves/tests/samples_tests.rs
index b2db1ac..bf8e716 100644
--- a/implementations/rust/preserves/tests/samples_tests.rs
+++ b/implementations/rust/preserves/tests/samples_tests.rs
@@ -27,21 +27,21 @@ fn decode_all(bytes: &'_ [u8]) -> Result<Vec<IOValue>, std::io::Error> {
         println!("{:?} ==> {:?}", name, case);
         match case {
             TestCase::Test(ref bin, ref val) => {
-                assert_eq!(&decode_all(&PackedWriter::encode(val)?[..])?, &[val.clone()]);
+                assert_eq!(&decode_all(&PackedWriter::encode_iovalue(val)?[..])?, &[val.clone()]);
                 assert_eq!(&decode_all(&bin[..])?, &[val.clone()]);
-                assert_eq!(&PackedWriter::encode(val)?, bin);
+                assert_eq!(&PackedWriter::encode_iovalue(val)?, bin);
             }
             TestCase::NondeterministicTest(ref bin, ref val) => {
                 // The test cases in samples.pr are carefully written
                 // so that while strictly "nondeterministic", the
                 // order of keys in encoded dictionaries follows
                 // Preserves canonical order.
-                assert_eq!(&PackedWriter::encode(val)?, bin);
-                assert_eq!(&decode_all(&PackedWriter::encode(val)?[..])?, &[val.clone()]);
+                assert_eq!(&PackedWriter::encode_iovalue(val)?, bin);
+                assert_eq!(&decode_all(&PackedWriter::encode_iovalue(val)?[..])?, &[val.clone()]);
                 assert_eq!(&decode_all(&bin[..])?, &[val.clone()]);
             }
             TestCase::DecodeTest(ref bin, ref val) => {
-                assert_eq!(&decode_all(&PackedWriter::encode(val)?[..])?, &[val.clone()]);
+                assert_eq!(&decode_all(&PackedWriter::encode_iovalue(val)?[..])?, &[val.clone()]);
                 assert_eq!(&decode_all(&bin[..])?, &[val.clone()]);
             }
             TestCase::ParseError(_) => (),