diff --git a/pkg/guid/guid.go b/pkg/guid/guid.go
index 3c112d2..d0595f6 100644
--- a/pkg/guid/guid.go
+++ b/pkg/guid/guid.go
@@ -1,19 +1,42 @@
+// Package guid provides a GUID type. The backing structure for a GUID is
+// identical to that used by the golang.org/x/sys/windows GUID type.
+// There are two main binary encodings used for a GUID, the big-endian encoding,
+// and the Windows (mixed-endian) encoding. See here for details:
+// https://en.wikipedia.org/wiki/Universally_unique_identifier#Encoding
 package guid
 
 import (
 	"crypto/rand"
+	"encoding"
 	"encoding/binary"
-	"encoding/json"
 	"fmt"
 	"strconv"
-	"strings"
 
-	"github.com/pkg/errors"
 	"golang.org/x/sys/windows"
 )
 
-var _ = (json.Marshaler)(GUID{})
-var _ = (json.Unmarshaler)(&GUID{})
+// Variant specifies which GUID variant (or "type") of the GUID. It determines
+// how the entirety of the rest of the GUID is interpreted.
+type Variant uint8
+
+// The variants specified by RFC 4122.
+const (
+	// VariantUnknown specifies a GUID variant which does not conform to one of
+	// the variant encodings specified in RFC 4122.
+	VariantUnknown Variant = iota
+	VariantNCS
+	VariantRFC4122
+	VariantMicrosoft
+	VariantFuture
+)
+
+// Version specifies how the bits in the GUID were generated. For instance, a
+// version 4 GUID is randomly generated, and a version 5 is generated from the
+// hash of an input string.
+type Version uint8
+
+var _ = (encoding.TextMarshaler)(GUID{})
+var _ = (encoding.TextUnmarshaler)(&GUID{})
 
 // GUID represents a GUID/UUID. It has the same structure as
 // golang.org/x/sys/windows.GUID so that it can be used with functions expecting
@@ -29,15 +52,50 @@ func NewV4() (GUID, error) {
 		return GUID{}, err
 	}
 
-	var g GUID
-	g.Data1 = binary.LittleEndian.Uint32(b[0:4])
-	g.Data2 = binary.LittleEndian.Uint16(b[4:6])
-	g.Data3 = binary.LittleEndian.Uint16(b[6:8])
-	copy(g.Data4[:], b[8:16])
+	b[6] = (b[6] & 0x0f) | 0x40 // Version 4 (randomly generated)
+	b[8] = (b[8] & 0x3f) | 0x80 // RFC4122 variant
 
-	g.Data3 = (g.Data3 & 0x0fff) | 0x4000   // Version 4 (randomly generated)
-	g.Data4[0] = (g.Data4[0] & 0x3f) | 0x80 // RFC4122 variant
-	return g, nil
+	return FromArray(b), nil
+}
+
+func fromArray(b [16]byte, order binary.ByteOrder) GUID {
+	var g GUID
+	g.Data1 = order.Uint32(b[0:4])
+	g.Data2 = order.Uint16(b[4:6])
+	g.Data3 = order.Uint16(b[6:8])
+	copy(g.Data4[:], b[8:16])
+	return g
+}
+
+func (g GUID) toArray(order binary.ByteOrder) [16]byte {
+	b := [16]byte{}
+	order.PutUint32(b[0:4], g.Data1)
+	order.PutUint16(b[4:6], g.Data2)
+	order.PutUint16(b[6:8], g.Data3)
+	copy(b[8:16], g.Data4[:])
+	return b
+}
+
+// FromArray constructs a GUID from a big-endian encoding array of 16 bytes.
+func FromArray(b [16]byte) GUID {
+	return fromArray(b, binary.BigEndian)
+}
+
+// ToArray returns an array of 16 bytes representing the GUID in big-endian
+// encoding.
+func (g GUID) ToArray() [16]byte {
+	return g.toArray(binary.BigEndian)
+}
+
+// FromWindowsArray constructs a GUID from a Windows encoding array of bytes.
+func FromWindowsArray(b [16]byte) GUID {
+	return fromArray(b, binary.LittleEndian)
+}
+
+// ToWindowsArray returns an array of 16 bytes representing the GUID in Windows
+// encoding.
+func (g GUID) ToWindowsArray() [16]byte {
+	return g.toArray(binary.LittleEndian)
 }
 
 func (g GUID) String() string {
@@ -55,36 +113,36 @@ func (g GUID) String() string {
 // format.
 func FromString(s string) (GUID, error) {
 	if len(s) != 36 {
-		return GUID{}, errors.New("invalid GUID format (length)")
+		return GUID{}, fmt.Errorf("invalid GUID %q", s)
 	}
 	if s[8] != '-' || s[13] != '-' || s[18] != '-' || s[23] != '-' {
-		return GUID{}, errors.New("invalid GUID format (dashes)")
+		return GUID{}, fmt.Errorf("invalid GUID %q", s)
 	}
 
 	var g GUID
 
 	data1, err := strconv.ParseUint(s[0:8], 16, 32)
 	if err != nil {
-		return GUID{}, errors.Wrap(err, "invalid GUID format (Data1)")
+		return GUID{}, fmt.Errorf("invalid GUID %q", s)
 	}
 	g.Data1 = uint32(data1)
 
 	data2, err := strconv.ParseUint(s[9:13], 16, 16)
 	if err != nil {
-		return GUID{}, errors.Wrap(err, "invalid GUID format (Data2)")
+		return GUID{}, fmt.Errorf("invalid GUID %q", s)
 	}
 	g.Data2 = uint16(data2)
 
 	data3, err := strconv.ParseUint(s[14:18], 16, 16)
 	if err != nil {
-		return GUID{}, errors.Wrap(err, "invalid GUID format (Data3)")
+		return GUID{}, fmt.Errorf("invalid GUID %q", s)
 	}
 	g.Data3 = uint16(data3)
 
 	for i, x := range []int{19, 21, 24, 26, 28, 30, 32, 34} {
 		v, err := strconv.ParseUint(s[x:x+2], 16, 8)
 		if err != nil {
-			return GUID{}, errors.Wrap(err, "invalid GUID format (Data4)")
+			return GUID{}, fmt.Errorf("invalid GUID %q", s)
 		}
 		g.Data4[i] = uint8(v)
 	}
@@ -92,16 +150,35 @@ func FromString(s string) (GUID, error) {
 	return g, nil
 }
 
-// MarshalJSON marshals the GUID to JSON representation and returns it as a
-// slice of bytes.
-func (g GUID) MarshalJSON() ([]byte, error) {
-	return json.Marshal(g.String())
+// Variant returns the GUID variant, as defined in RFC 4122.
+func (g GUID) Variant() Variant {
+	b := g.Data4[0]
+	if b&0x80 == 0 {
+		return VariantNCS
+	} else if b&0xc0 == 0x80 {
+		return VariantRFC4122
+	} else if b&0xe0 == 0xc0 {
+		return VariantMicrosoft
+	} else if b&0xe0 == 0xe0 {
+		return VariantFuture
+	}
+	return VariantUnknown
 }
 
-// UnmarshalJSON unmarshals a GUID from JSON representation and sets itself to
-// the unmarshaled GUID.
-func (g *GUID) UnmarshalJSON(data []byte) error {
-	g2, err := FromString(strings.Trim(string(data), "\""))
+// Version returns the GUID version, as defined in RFC 4122.
+func (g GUID) Version() Version {
+	return Version((g.Data3 & 0xF000) >> 12)
+}
+
+// MarshalText returns the textual representation of the GUID.
+func (g GUID) MarshalText() ([]byte, error) {
+	return []byte(g.String()), nil
+}
+
+// UnmarshalText takes the textual representation of a GUID, and unmarhals it
+// into this GUID.
+func (g *GUID) UnmarshalText(text []byte) error {
+	g2, err := FromString(string(text))
 	if err != nil {
 		return err
 	}
diff --git a/pkg/guid/guid_test.go b/pkg/guid/guid_test.go
index 9bf37e6..b229cc6 100644
--- a/pkg/guid/guid_test.go
+++ b/pkg/guid/guid_test.go
@@ -6,26 +6,77 @@ import (
 	"testing"
 )
 
-func Test_New(t *testing.T) {
+func mustNewV4(t *testing.T) GUID {
 	g, err := NewV4()
 	if err != nil {
 		t.Fatal(err)
 	}
-	g2, err := NewV4()
+	return g
+}
+
+func mustFromString(t *testing.T, s string) GUID {
+	g, err := FromString(s)
 	if err != nil {
 		t.Fatal(err)
 	}
+	return g
+}
+
+func Test_NewV4IsUnique(t *testing.T) {
+	g := mustNewV4(t)
+	g2 := mustNewV4(t)
 	if g == g2 {
 		t.Fatalf("GUIDs are equal: %s, %s", g, g2)
 	}
 }
 
+func Test_V4HasCorrectVersionAndVariant(t *testing.T) {
+	g := mustNewV4(t)
+	if g.Version() != 4 {
+		t.Fatalf("Version is not 4: %s", g)
+	}
+	if g.Variant() != VariantRFC4122 {
+		t.Fatalf("Variant is not RFC4122: %s", g)
+	}
+}
+
+func Test_ToArray(t *testing.T) {
+	g := mustFromString(t, "73c39589-192e-4c64-9acf-6c5d0aa18528")
+	b := g.ToArray()
+	expected := [16]byte{0x73, 0xc3, 0x95, 0x89, 0x19, 0x2e, 0x4c, 0x64, 0x9a, 0xcf, 0x6c, 0x5d, 0x0a, 0xa1, 0x85, 0x28}
+	if b != expected {
+		t.Fatalf("GUID does not match array form: %x, %x", expected, b)
+	}
+}
+
+func Test_FromArrayAndBack(t *testing.T) {
+	b := [16]byte{0x73, 0xc3, 0x95, 0x89, 0x19, 0x2e, 0x4c, 0x64, 0x9a, 0xcf, 0x6c, 0x5d, 0x0a, 0xa1, 0x85, 0x28}
+	b2 := FromArray(b).ToArray()
+	if b != b2 {
+		t.Fatalf("Arrays do not match: %x, %x", b, b2)
+	}
+}
+
+func Test_ToWindowsArray(t *testing.T) {
+	g := mustFromString(t, "73c39589-192e-4c64-9acf-6c5d0aa18528")
+	b := g.ToWindowsArray()
+	expected := [16]byte{0x89, 0x95, 0xc3, 0x73, 0x2e, 0x19, 0x64, 0x4c, 0x9a, 0xcf, 0x6c, 0x5d, 0x0a, 0xa1, 0x85, 0x28}
+	if b != expected {
+		t.Fatalf("GUID does not match array form: %x, %x", expected, b)
+	}
+}
+
+func Test_FromWindowsArrayAndBack(t *testing.T) {
+	b := [16]byte{0x73, 0xc3, 0x95, 0x89, 0x19, 0x2e, 0x4c, 0x64, 0x9a, 0xcf, 0x6c, 0x5d, 0x0a, 0xa1, 0x85, 0x28}
+	b2 := FromWindowsArray(b).ToWindowsArray()
+	if b != b2 {
+		t.Fatalf("Arrays do not match: %x, %x", b, b2)
+	}
+}
+
 func Test_FromString(t *testing.T) {
 	orig := "8e35239e-2084-490e-a3db-ab18ee0744cb"
-	g, err := FromString(orig)
-	if err != nil {
-		t.Fatal(err)
-	}
+	g := mustFromString(t, orig)
 	s := g.String()
 	if orig != s {
 		t.Fatalf("GUIDs not equal: %s, %s", orig, s)
@@ -33,10 +84,7 @@ func Test_FromString(t *testing.T) {
 }
 
 func Test_MarshalJSON(t *testing.T) {
-	g, err := NewV4()
-	if err != nil {
-		t.Fatal(err)
-	}
+	g := mustNewV4(t)
 	j, err := json.Marshal(g)
 	if err != nil {
 		t.Fatal(err)
@@ -51,10 +99,7 @@ func Test_MarshalJSON_Nested(t *testing.T) {
 	type test struct {
 		G GUID
 	}
-	g, err := NewV4()
-	if err != nil {
-		t.Fatal(err)
-	}
+	g := mustNewV4(t)
 	t1 := test{g}
 	j, err := json.Marshal(t1)
 	if err != nil {
@@ -67,10 +112,7 @@ func Test_MarshalJSON_Nested(t *testing.T) {
 }
 
 func Test_UnmarshalJSON(t *testing.T) {
-	g, err := NewV4()
-	if err != nil {
-		t.Fatal(err)
-	}
+	g := mustNewV4(t)
 	j, err := json.Marshal(g)
 	if err != nil {
 		t.Fatal(err)
@@ -88,10 +130,7 @@ func Test_UnmarshalJSON_Nested(t *testing.T) {
 	type test struct {
 		G GUID
 	}
-	g, err := NewV4()
-	if err != nil {
-		t.Fatal(err)
-	}
+	g := mustNewV4(t)
 	t1 := test{g}
 	j, err := json.Marshal(t1)
 	if err != nil {