diff --git a/cmd/obitools/obifind/main.go b/cmd/obitools/obifind/main.go
index b51ef3e..0b3f38a 100644
--- a/cmd/obitools/obifind/main.go
+++ b/cmd/obitools/obifind/main.go
@@ -22,26 +22,26 @@ func main() {
 	}
 
 	switch {
-	case obifind.CLIRequestsPathForTaxid() >= 0:
+	case obifind.CLIRequestsPathForTaxid() != "NA":
 		taxonomy, err := obifind.CLILoadSelectedTaxonomy()
 		if err != nil {
 			fmt.Printf("%+v", err)
 		}
 
-		taxon, err := taxonomy.Taxon(obifind.CLIRequestsPathForTaxid())
+		taxon := taxonomy.Taxon(obifind.CLIRequestsPathForTaxid())
 
-		if err != nil {
+		if taxon == nil {
 			fmt.Printf("%+v", err)
 		}
 
-		s, err := taxon.Path()
+		s := taxon.Path()
 
 		if err != nil {
 			fmt.Printf("%+v", err)
 		}
 
 		obifind.TaxonWriter(s.Iterator(),
-			fmt.Sprintf("path:%d", taxon.Taxid()))
+			fmt.Sprintf("path:%s", taxon.String()))
 
 	case len(args) == 0:
 		taxonomy, err := obifind.CLILoadSelectedTaxonomy()
diff --git a/pkg/obiformats/csv_writer.go b/pkg/obiformats/csv_writer.go
index 7d22ff9..acfb604 100644
--- a/pkg/obiformats/csv_writer.go
+++ b/pkg/obiformats/csv_writer.go
@@ -30,14 +30,10 @@ func CSVRecord(sequence *obiseq.BioSequence, opt Options) []string {
 
 	if opt.CSVTaxon() {
 		taxid := sequence.Taxid()
-		sn, ok := sequence.GetAttribute("scientific_name")
+		sn, ok := sequence.GetStringAttribute("scientific_name")
 
 		if !ok {
-			if taxid == 1 {
-				sn = "root"
-			} else {
-				sn = opt.CSVNAValue()
-			}
+			sn = opt.CSVNAValue()
 		}
 
 		record = append(record, fmt.Sprint(taxid), fmt.Sprint(sn))
diff --git a/pkg/obiformats/ncbitaxdump/read.go b/pkg/obiformats/ncbitaxdump/read.go
index c304961..ae5b7e3 100644
--- a/pkg/obiformats/ncbitaxdump/read.go
+++ b/pkg/obiformats/ncbitaxdump/read.go
@@ -7,7 +7,6 @@ import (
 	"io"
 	"os"
 	"path"
-	"strconv"
 	"strings"
 
 	log "github.com/sirupsen/logrus"
@@ -26,24 +25,16 @@ func loadNodeTable(reader io.Reader, taxonomy *obitax.Taxonomy) {
 
 	for record, err := file.Read(); err == nil; record, err = file.Read() {
 		n++
-		taxid, err := strconv.Atoi(strings.TrimSpace(record[0]))
-
-		if err != nil {
-			log.Panicf("Cannot read taxon taxid at line %d: %v", n, err)
-		}
-
-		parent, err := strconv.Atoi(strings.TrimSpace(record[1]))
-
-		if err != nil {
-			log.Panicf("Cannot read taxon parent taxid at line %d: %v", n, err)
-		}
-
+		taxid := strings.TrimSpace(record[0])
+		parent := strings.TrimSpace(record[1])
 		rank := strings.TrimSpace(record[2])
 
-		taxonomy.AddNewTaxa(taxid, parent, rank, true, true)
-	}
+		_, err := taxonomy.AddTaxon(taxid, parent, rank, taxid == "1", false)
 
-	taxonomy.ReindexParent()
+		if err != nil {
+			log.Fatalf("Error adding taxon %s: %v\n", taxid, err)
+		}
+	}
 }
 
 func loadNameTable(reader io.Reader, taxonomy *obitax.Taxonomy, onlysn bool) int {
@@ -65,18 +56,14 @@ func loadNameTable(reader io.Reader, taxonomy *obitax.Taxonomy, onlysn bool) int
 		}
 
 		record := strings.Split(string(line), "|")
-		taxid, err := strconv.Atoi(strings.TrimSpace(record[0]))
-
-		if err != nil {
-			log.Panicf("Cannot read taxon name taxid at line %d: %v", l, err)
-		}
+		taxid := strings.TrimSpace(record[0])
 
 		name := strings.TrimSpace(record[1])
 		classname := strings.TrimSpace(record[3])
 
 		if !onlysn || classname == "scientific name" {
 			n++
-			taxonomy.AddNewName(taxid, &name, &classname)
+			taxonomy.Taxon(taxid).SetName(name, classname)
 		}
 	}
 
@@ -94,18 +81,10 @@ func loadMergedTable(reader io.Reader, taxonomy *obitax.Taxonomy) int {
 
 	for record, err := file.Read(); err == nil; record, err = file.Read() {
 		n++
-		oldtaxid, err := strconv.Atoi(strings.TrimSpace(record[0]))
+		oldtaxid := strings.TrimSpace(record[0])
+		newtaxid := strings.TrimSpace(record[1])
 
-		if err != nil {
-			log.Panicf("Cannot read alias taxid at line %d: %v", n, err)
-		}
-		newtaxid, err := strconv.Atoi(strings.TrimSpace(record[1]))
-
-		if err != nil {
-			log.Panicf("Cannot read alias new taxid at line %d: %v", n, err)
-		}
-
-		taxonomy.AddNewAlias(newtaxid, oldtaxid)
+		taxonomy.AddAlias(newtaxid, oldtaxid, false)
 	}
 
 	return n
@@ -113,7 +92,7 @@ func loadMergedTable(reader io.Reader, taxonomy *obitax.Taxonomy) int {
 
 func LoadNCBITaxDump(directory string, onlysn bool) (*obitax.Taxonomy, error) {
 
-	taxonomy := obitax.NewTaxonomy()
+	taxonomy := obitax.NewTaxonomy("NCBI Taxonomy", "taxon", "[[:digit:]]")
 
 	//
 	// Load the Taxonomy nodes
diff --git a/pkg/obilua/obiseq.go b/pkg/obilua/obiseq.go
index d99c634..e7967ab 100644
--- a/pkg/obilua/obiseq.go
+++ b/pkg/obilua/obiseq.go
@@ -147,10 +147,10 @@ func bioSequenceGetSetCount(luaState *lua.LState) int {
 func bioSequenceGetSetTaxid(luaState *lua.LState) int {
 	s := checkBioSequence(luaState)
 	if luaState.GetTop() == 2 {
-		s.SetTaxid(luaState.CheckInt(2))
+		s.SetTaxid(luaState.CheckString(2))
 		return 0
 	}
-	luaState.Push(lua.LNumber(s.Taxid()))
+	luaState.Push(lua.LString(s.Taxid()))
 	return 1
 }
 
diff --git a/pkg/obioptions/version.go b/pkg/obioptions/version.go
index 93f0bee..231d812 100644
--- a/pkg/obioptions/version.go
+++ b/pkg/obioptions/version.go
@@ -7,7 +7,7 @@ import (
 // TODO: The version number is extracted from git. This induces that the version
 // corresponds to the last commit, and not the one when the file will be
 // commited
-var _Commit = "3e00d39"
+var _Commit = "9471fed"
 var _Version = "Release 4.2.0"
 
 // Version returns the version of the obitools package.
diff --git a/pkg/obiseq/attributes.go b/pkg/obiseq/attributes.go
index de4ea31..5a604d9 100644
--- a/pkg/obiseq/attributes.go
+++ b/pkg/obiseq/attributes.go
@@ -9,17 +9,18 @@ import (
 )
 
 // AttributeKeys returns the keys of the attributes in the BioSequence.
+// It optionally skips keys associated with container values based on the skip_container parameter.
 //
-// It does not take any parameters.
+// Parameters:
+//   - skip_container: A boolean indicating whether to skip keys associated with a container value.
 //
 // Returns:
-//
-//	[]string: The keys of the BioSequence.
-func (s *BioSequence) AttributeKeys(skip_map bool) obiutils.Set[string] {
+//   - A set of strings containing the keys of the BioSequence attributes.
+func (s *BioSequence) AttributeKeys(skip_container bool) obiutils.Set[string] {
 	keys := obiutils.MakeSet[string]()
 
 	for k, v := range s.Annotations() {
-		if !skip_map || !obiutils.IsAMap(v) {
+		if !skip_container || !obiutils.IsAContainer(v) {
 			keys.Add(k)
 		}
 	}
@@ -27,17 +28,18 @@ func (s *BioSequence) AttributeKeys(skip_map bool) obiutils.Set[string] {
 	return keys
 }
 
-// Keys returns the keys of the BioSequence.
+// Keys returns the keys of the BioSequence, including standard keys and attribute keys.
 //
-// It returns a slice of strings containing the keys of the BioSequence.
-// The keys include "id", "sequence", "qualities", and the attribute keys
-// of the BioSequence.
+// It returns a set of strings containing the keys of the BioSequence.
+// The keys include "id", "sequence", "qualities", and the attribute keys of the BioSequence.
+//
+// Parameters:
+//   - skip_container: A boolean indicating whether to skip keys associated with container values.
 //
 // Returns:
-//
-//	[]string: The keys of the BioSequence.
-func (s *BioSequence) Keys(skip_map bool) obiutils.Set[string] {
-	keys := s.AttributeKeys(skip_map)
+//   - A set of strings containing the keys of the BioSequence.
+func (s *BioSequence) Keys(skip_container bool) obiutils.Set[string] {
+	keys := s.AttributeKeys(skip_container)
 	keys.Add("id")
 
 	if s.HasSequence() {
@@ -53,10 +55,10 @@ func (s *BioSequence) Keys(skip_map bool) obiutils.Set[string] {
 // HasAttribute checks if the BioSequence has the specified attribute.
 //
 // Parameters:
-// - key: a string representing the attribute key to check.
+//   - key: A string representing the attribute key to check.
 //
 // Returns:
-// - a boolean indicating whether the BioSequence has the attribute.
+//   - A boolean indicating whether the BioSequence has the attribute.
 func (s *BioSequence) HasAttribute(key string) bool {
 	if key == "id" {
 		return true
@@ -386,31 +388,14 @@ func (s *BioSequence) SetCount(count int) {
 	s.SetAttribute("count", count)
 }
 
-// Taxid returns the taxonomic ID associated with the BioSequence.
-//
-// It retrieves the "taxid" attribute from the BioSequence's attributes map.
-// If the attribute is not found, the function returns 1 as the default taxonomic ID.
-// The taxid 1 corresponds to the root taxonomic level.
-//
-// The function returns an integer representing the taxonomic ID.
-func (s *BioSequence) Taxid() int {
-	taxid, ok := s.GetIntAttribute("taxid")
-
-	if !ok {
-		taxid = 1
-	}
-
-	return taxid
-}
-
 // SetTaxid sets the taxid for the BioSequence.
 //
 // Parameters:
 //
 //	taxid - the taxid to set.
-func (s *BioSequence) SetTaxid(taxid int) {
-	if taxid < 1 {
-		taxid = 1
+func (s *BioSequence) SetTaxid(taxid string) {
+	if taxid == "" {
+		taxid = "NA"
 	}
 	s.SetAttribute("taxid", taxid)
 }
diff --git a/pkg/obiseq/biosequence.go b/pkg/obiseq/biosequence.go
index 101e333..3a5b5d2 100644
--- a/pkg/obiseq/biosequence.go
+++ b/pkg/obiseq/biosequence.go
@@ -18,6 +18,7 @@ import (
 	"unsafe"
 
 	"git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obioptions"
+	"git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obitax"
 	"git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obiutils"
 	log "github.com/sirupsen/logrus"
 )
@@ -63,6 +64,7 @@ type BioSequence struct {
 	sequence    []byte // The sequence itself, it is accessible by the methode Sequence
 	qualities   []byte // The quality scores of the sequence.
 	feature     []byte
+	taxon       *obitax.Taxon
 	paired      *BioSequence // A pointer to the paired sequence
 	revcomp     *BioSequence // A pointer to the reverse complemented sequence
 	annotations Annotation
@@ -90,6 +92,7 @@ func NewEmptyBioSequence(preallocate int) *BioSequence {
 		sequence:    seq,
 		qualities:   nil,
 		feature:     nil,
+		taxon:       nil,
 		paired:      nil,
 		revcomp:     nil,
 		annotations: nil,
@@ -223,7 +226,7 @@ func (s *BioSequence) HasDefinition() bool {
 // No parameters.
 // Returns a boolean.
 func (s *BioSequence) HasSequence() bool {
-	return s.sequence != nil && len(s.sequence) > 0
+	return len(s.sequence) > 0
 }
 
 // Sequence returns the sequence of the BioSequence.
@@ -258,7 +261,7 @@ func (s *BioSequence) Len() int {
 // This function does not have any parameters.
 // It returns a boolean value indicating whether the BioSequence has qualities.
 func (s *BioSequence) HasQualities() bool {
-	return s.qualities != nil && len(s.qualities) > 0
+	return len(s.qualities) > 0
 }
 
 // Qualities returns the sequence quality scores of the BioSequence.
diff --git a/pkg/obiseq/taxonomy_classifier.go b/pkg/obiseq/taxonomy_classifier.go
new file mode 100644
index 0000000..0eba39e
--- /dev/null
+++ b/pkg/obiseq/taxonomy_classifier.go
@@ -0,0 +1,79 @@
+package obiseq
+
+import (
+	"git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obitax"
+	log "github.com/sirupsen/logrus"
+)
+
+// TaxonomyClassifier is a function that creates a new instance of the BioSequenceClassifier
+// for taxonomic classification based on a given taxonomic rank, taxonomy, and abort flag.
+//
+// Parameters:
+// - taxonomicRank: the taxonomic rank to classify the sequences at.
+// - taxonomy: the taxonomy object used for classification.
+// - abortOnMissing: a flag indicating whether to abort if a taxon is missing in the taxonomy.
+//
+// Return:
+// - *obiseq.BioSequenceClassifier: the new instance of the BioSequenceClassifier.
+func TaxonomyClassifier(taxonomicRank string,
+	taxonomy *obitax.Taxonomy,
+	abortOnMissing bool) *BioSequenceClassifier {
+
+	keys := make(map[*obitax.TaxNode]int)
+	codes := make([]*obitax.TaxNode, 1)
+	codes[0] = nil
+	keys[nil] = 0
+
+	code := func(sequence *BioSequence) int {
+		taxon := sequence.Taxon(taxonomy)
+		if taxon != nil {
+			ttaxon := taxon.TaxonAtRank(taxonomicRank)
+			if abortOnMissing && ttaxon == nil {
+				log.Fatalf("Taxon at rank %s not found in taxonomy for taxid %d", taxonomicRank, taxon.String())
+			}
+		} else {
+			if abortOnMissing {
+				log.Fatalf("Sequence %s: Taxid %s not found in taxonomy",
+					sequence.Id(),
+					sequence.Taxid())
+			}
+			taxon = nil
+		}
+
+		k, ok := keys[taxon.Node]
+
+		if ok {
+			return k
+		}
+
+		k = len(codes)
+		keys[taxon.Node] = k
+		codes = append(codes, taxon.Node)
+
+		return k
+	}
+
+	value := func(k int) string {
+		taxon := codes[k]
+		return taxon.ScientificName()
+	}
+
+	reset := func() {
+		keys = make(map[*obitax.TaxNode]int)
+		codes = make([]*obitax.TaxNode, 1)
+		codes[0] = nil
+		keys[nil] = 0
+	}
+
+	clone := func() *BioSequenceClassifier {
+		return TaxonomyClassifier(taxonomicRank, taxonomy, abortOnMissing)
+	}
+
+	c := BioSequenceClassifier{
+		Code:  code,
+		Value: value,
+		Reset: reset,
+		Clone: clone,
+		Type:  "TaxonomyClassifier"}
+	return &c
+}
diff --git a/pkg/obiseq/taxonomy_lca.go b/pkg/obiseq/taxonomy_lca.go
new file mode 100644
index 0000000..5ed32ce
--- /dev/null
+++ b/pkg/obiseq/taxonomy_lca.go
@@ -0,0 +1,131 @@
+package obiseq
+
+import (
+	"math"
+	"strings"
+
+	"git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obitax"
+	log "github.com/sirupsen/logrus"
+)
+
+func (sequence *BioSequence) TaxonomicDistribution(taxonomy *obitax.Taxonomy) map[*obitax.TaxNode]int {
+	taxids := sequence.StatsOn(MakeStatsOnDescription("taxid"), "na")
+	taxons := make(map[*obitax.TaxNode]int, len(taxids))
+
+	for taxid, v := range taxids {
+		t := taxonomy.Taxon(taxid)
+		if t == nil {
+			log.Fatalf(
+				"On sequence %s taxid %s is not defined in taxonomy: %s",
+				sequence.Id(),
+				taxid,
+				taxonomy.Name())
+		}
+		taxons[t.Node] = v
+	}
+	return taxons
+}
+
+func (sequence *BioSequence) LCA(taxonomy *obitax.Taxonomy, threshold float64) (*obitax.Taxon, float64, int) {
+	taxons := sequence.TaxonomicDistribution(taxonomy)
+	paths := make(map[*obitax.TaxNode]*obitax.TaxonSlice, len(taxons))
+	answer := (*obitax.TaxNode)(nil)
+	rans := 1.0
+	granTotal := 0
+
+	for t, w := range taxons {
+		p := (&obitax.Taxon{Taxonomy: taxonomy,
+			Node: t,
+		}).Path()
+		if p == nil {
+			log.Panicf("Sequence %s: taxonomic path cannot be retreived from Taxid %d : %v", sequence.Id(), t.String(taxonomy.Code()))
+		}
+
+		p.Reverse(true)
+		paths[t] = p
+		answer = p.Get(0)
+		granTotal += w
+	}
+
+	rmax := 1.0
+	levels := make(map[*obitax.TaxNode]int, len(paths))
+	taxonMax := answer
+
+	for i := 0; rmax >= threshold; i++ {
+		answer = taxonMax
+		rans = rmax
+		taxonMax = nil
+		total := 0
+		for taxon, weight := range taxons {
+			path := paths[taxon]
+			if path.Len() > i {
+				levels[path.Get(i)] += weight
+			}
+			total += weight
+		}
+		weighMax := 0
+		for taxon, weight := range levels {
+			if weight > weighMax {
+				weighMax = weight
+				taxonMax = taxon
+			}
+		}
+
+		if total > 0 {
+			rmax *= float64(weighMax) / float64(total)
+		} else {
+			rmax = 0.0
+		}
+
+		for taxon := range levels {
+			delete(levels, taxon)
+		}
+		for taxon := range taxons {
+			path := paths[taxon]
+			if i < path.Len() {
+				if path.Get(i) != taxonMax {
+					delete(paths, taxon)
+					delete(taxons, taxon)
+				}
+			}
+		}
+		// if taxonMax != nil {
+		// 	log.Println("@@@>", i, taxonMax.ScientificName(), taxonMax.Taxid(), rans, weighMax, total, rmax)
+		// } else {
+		// 	log.Println("@@@>", "--", 0, rmax)
+		// }
+	}
+	// log.Println("###>", answer.ScientificName(), answer.Taxid(), rans)
+	// log.Print("========================================")
+	return &obitax.Taxon{Taxonomy: taxonomy, Node: answer}, rans, granTotal
+
+}
+
+func AddLCAWorker(taxonomy *obitax.Taxonomy, slot_name string, threshold float64) SeqWorker {
+
+	if !strings.HasSuffix(slot_name, "taxid") {
+		slot_name = slot_name + "_taxid"
+	}
+
+	lca_error := strings.Replace(slot_name, "taxid", "error", 1)
+	if lca_error == "error" {
+		lca_error = "lca_error"
+	}
+
+	lca_name := strings.Replace(slot_name, "taxid", "name", 1)
+	if lca_name == "name" {
+		lca_name = "scientific_name"
+	}
+
+	f := func(sequence *BioSequence) (BioSequenceSlice, error) {
+		lca, rans, _ := sequence.LCA(taxonomy, threshold)
+
+		sequence.SetAttribute(slot_name, lca.String())
+		sequence.SetAttribute(lca_name, lca.ScientificName())
+		sequence.SetAttribute(lca_error, math.Round((1-rans)*1000)/1000)
+
+		return BioSequenceSlice{sequence}, nil
+	}
+
+	return f
+}
diff --git a/pkg/obiseq/taxonomy_methods.go b/pkg/obiseq/taxonomy_methods.go
new file mode 100644
index 0000000..b6b46fa
--- /dev/null
+++ b/pkg/obiseq/taxonomy_methods.go
@@ -0,0 +1,106 @@
+package obiseq
+
+import (
+	"git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obitax"
+)
+
+func (s *BioSequence) Taxon(taxonomy *obitax.Taxonomy) *obitax.Taxon {
+	taxid := s.Taxid()
+	if taxid == "NA" {
+		return nil
+	}
+	return taxonomy.Taxon(taxid)
+}
+
+// Taxid returns the taxonomic ID associated with the BioSequence.
+//
+// It retrieves the "taxid" attribute from the BioSequence's attributes map.
+// If the attribute is not found, the function returns 1 as the default taxonomic ID.
+// The taxid 1 corresponds to the root taxonomic level.
+//
+// The function returns an integer representing the taxonomic ID.
+func (s *BioSequence) Taxid() (taxid string) {
+	var ok bool
+	if s.taxon != nil {
+		taxid = s.taxon.String()
+		ok = true
+	} else {
+		taxid, ok = s.GetStringAttribute("taxid")
+	}
+
+	if !ok {
+		taxid = "NA"
+	}
+
+	return taxid
+}
+
+// Setting the taxon at a given rank for a given sequence.
+//
+// Two attributes are added to the sequence. One named by the rank name stores
+// the taxid, a second named by the rank name suffixed with '_name' contains the
+// Scientific name of the genus.
+// If the taxon at the given rank doesn't exist for the taxonomy annotation
+// of the sequence, nothing happens.
+func (sequence *BioSequence) SetTaxonAtRank(taxonomy *obitax.Taxonomy, rank string) *obitax.Taxon {
+	var taxonAtRank *obitax.Taxon
+
+	taxon := sequence.Taxon(taxonomy)
+	taxonAtRank = nil
+	if taxon != nil {
+		taxonAtRank = taxon.TaxonAtRank(rank)
+		if taxonAtRank != nil {
+			// log.Printf("Taxid: %d  Rank: %s --> proposed : %d (%s)", taxid, rank, taxonAtRank.taxid, *(taxonAtRank.scientificname))
+			sequence.SetAttribute(rank+"_taxid", taxonAtRank.String())
+			sequence.SetAttribute(rank+"_name", taxonAtRank.ScientificName())
+		} else {
+			sequence.SetAttribute(rank+"_taxid", "NA")
+			sequence.SetAttribute(rank+"_name", "NA")
+		}
+	}
+
+	return taxonAtRank
+}
+
+// Setting the species of a sequence.
+func (sequence *BioSequence) SetSpecies(taxonomy *obitax.Taxonomy) *obitax.Taxon {
+	return sequence.SetTaxonAtRank(taxonomy, "species")
+}
+
+// Setting the genus of a sequence.
+func (sequence *BioSequence) SetGenus(taxonomy *obitax.Taxonomy) *obitax.Taxon {
+	return sequence.SetTaxonAtRank(taxonomy, "genus")
+}
+
+// Setting the family of a sequence.
+func (sequence *BioSequence) SetFamily(taxonomy *obitax.Taxonomy) *obitax.Taxon {
+	return sequence.SetTaxonAtRank(taxonomy, "family")
+}
+
+func (sequence *BioSequence) SetPath(taxonomy *obitax.Taxonomy) string {
+	taxon := sequence.Taxon(taxonomy)
+	path := taxon.Path()
+
+	tpath := path.String()
+	sequence.SetAttribute("taxonomic_path", tpath)
+
+	return tpath
+}
+
+func (sequence *BioSequence) SetScientificName(taxonomy *obitax.Taxonomy) string {
+	taxon := sequence.Taxon(taxonomy)
+	name := taxon.ScientificName()
+
+	sequence.SetAttribute("scienctific_name", name)
+
+	return name
+}
+
+func (sequence *BioSequence) SetTaxonomicRank(taxonomy *obitax.Taxonomy) string {
+	taxon := sequence.Taxon(taxonomy)
+	rank := taxon.Rank()
+
+	sequence.SetAttribute("taxonomic_rank", rank)
+
+	return rank
+}
diff --git a/pkg/obiseq/taxonomy_predicate.go b/pkg/obiseq/taxonomy_predicate.go
new file mode 100644
index 0000000..e8c2f24
--- /dev/null
+++ b/pkg/obiseq/taxonomy_predicate.go
@@ -0,0 +1,98 @@
+package obiseq
+
+import (
+	log "github.com/sirupsen/logrus"
+
+	"git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obitax"
+	"git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obiutils"
+)
+
+func IsAValidTaxon(taxonomy *obitax.Taxonomy, withAutoCorrection ...bool) SequencePredicate {
+	// deprecatedTaxidsWarning := make(map[string]bool)
+
+	autocorrection := false
+	if len(withAutoCorrection) > 0 {
+		autocorrection = withAutoCorrection[0]
+	}
+
+	f := func(sequence *BioSequence) bool {
+		taxon := sequence.Taxon(taxonomy)
+
+		if taxon != nil {
+			taxid := sequence.Taxid()
+			ttaxid := taxon.String()
+			if taxid != ttaxid {
+				if autocorrection {
+					sequence.SetTaxid(ttaxid)
+					log.Printf(
+						"Sequence %s : Taxid %d updated with %d",
+						sequence.Id(),
+						taxid,
+						ttaxid,
+					)
+				} //  else {
+				// 	if _, ok := deprecatedTaxidsWarning[taxid]; !ok {
+				// 		deprecatedTaxidsWarning[taxid] = true
+				// 		log.Printf("Taxid %d is deprecated and must be replaced by %d", taxid, taxon.taxid)
+				// 	}
+				// }
+			}
+		}
+
+		return taxon != nil
+	}
+
+	return f
+}
+
+// A function that takes a taxonomy and a taxid as arguments and returns a function that takes a
+// pointer to a BioSequence as an argument and returns a boolean.
+func IsSubCladeOf(taxonomy *obitax.Taxonomy, taxid string) SequencePredicate {
+	parent := taxonomy.Taxon(taxid)
+
+	if parent == nil {
+		log.Fatalf("Cannot find taxon : %s in taxonomy %s",
+			taxid,
+			taxonomy.Name())
+	}
+
+	f := func(sequence *BioSequence) bool {
+		taxon := sequence.Taxon(taxonomy)
+		return taxon != nil && taxon.IsSubCladeOf(parent)
+	}
+
+	return f
+}
+
+func IsSubCladeOfSlot(taxonomy *obitax.Taxonomy, key string) SequencePredicate {
+
+	f := func(sequence *BioSequence) bool {
+		val, ok := sequence.GetStringAttribute(key)
+
+		if ok {
+			parent := taxonomy.Taxon(val)
+			taxon := sequence.Taxon(taxonomy)
+			return parent != nil && taxon != nil && taxon.IsSubCladeOf(parent)
+		}
+
+		return false
+	}
+
+	return f
+}
+
+func HasRequiredRank(taxonomy *obitax.Taxonomy, rank string) SequencePredicate {
+
+	if !obiutils.Contains(taxonomy.RankList(), rank) {
+		log.Fatalf("%s is not a valid rank (allowed ranks are %v)",
+			rank,
+			taxonomy.RankList())
+	}
+
+	f := func(sequence *BioSequence) bool {
+		taxon := sequence.Taxon(taxonomy)
+		return taxon != nil && taxon.HasRankDefined(rank)
+	}
+
+	return f
+}
diff --git a/pkg/obiseq/taxonomy_workers.go b/pkg/obiseq/taxonomy_workers.go
new file mode 100644
index 0000000..241de96
--- /dev/null
+++ b/pkg/obiseq/taxonomy_workers.go
@@ -0,0 +1,64 @@
+package obiseq
+
+import (
+	"git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obitax"
+	"git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obiutils"
+	log "github.com/sirupsen/logrus"
+)
+
+func MakeSetTaxonAtRankWorker(taxonomy *obitax.Taxonomy, rank string) SeqWorker {
+
+	if !obiutils.Contains(taxonomy.RankList(), rank) {
+		log.Fatalf("%s is not a valid rank (allowed ranks are %v)",
+			rank,
+			taxonomy.RankList())
+	}
+
+	w := func(sequence *BioSequence) (BioSequenceSlice, error) {
+		sequence.SetTaxonAtRank(taxonomy, rank)
+		return BioSequenceSlice{sequence}, nil
+	}
+
+	return w
+}
+
+func MakeSetSpeciesWorker(taxonomy *obitax.Taxonomy) SeqWorker {
+
+	w := func(sequence *BioSequence) (BioSequenceSlice, error) {
+		sequence.SetSpecies(taxonomy)
+		return BioSequenceSlice{sequence}, nil
+	}
+
+	return w
+}
+
+func MakeSetGenusWorker(taxonomy *obitax.Taxonomy) SeqWorker {
+
+	w := func(sequence *BioSequence) (BioSequenceSlice, error) {
+		sequence.SetGenus(taxonomy)
+		return BioSequenceSlice{sequence}, nil
+	}
+
+	return w
+}
+
+func MakeSetFamilyWorker(taxonomy *obitax.Taxonomy) SeqWorker {
+
+	w := func(sequence *BioSequence) (BioSequenceSlice, error) {
+		sequence.SetFamily(taxonomy)
+		return BioSequenceSlice{sequence}, nil
+	}
+
+	return w
+}
+
+func MakeSetPathWorker(taxonomy *obitax.Taxonomy) SeqWorker {
+
+	w := func(sequence *BioSequence) (BioSequenceSlice, error) {
+		sequence.SetPath(taxonomy)
+		return BioSequenceSlice{sequence}, nil
+	}
+
+	return w
+
+}
diff --git a/pkg/obitax/filter_on_name.go b/pkg/obitax/filter_on_name.go
index d8f689b..b4321f5 100644
--- a/pkg/obitax/filter_on_name.go
+++ b/pkg/obitax/filter_on_name.go
@@ -4,31 +4,32 @@ import (
 	"regexp"
 )
 
-func (taxonomy *Taxonomy) IFilterOnName(name string, strict bool) *ITaxonSet {
+func (taxonomy *Taxonomy) IFilterOnName(name string, strict bool) *ITaxon {
 	if strict {
-		nodes, ok := taxonomy.index[name]
+		nodes, ok := taxonomy.index[taxonomy.names.Innerize(name)]
 		if ok {
 			return nodes.Iterator()
 		} else {
-			empty := make(TaxonSet)
-			return (&empty).Iterator()
+			empty := taxonomy.NewTaxonSet()
+			return empty.Iterator()
 		}
 	}
 
 	return taxonomy.Iterator().IFilterOnName(name, strict)
 }
 
-func (iterator *ITaxonSet) IFilterOnName(name string, strict bool) *ITaxonSet {
-	newIterator := NewITaxonSet()
-	sentTaxa := make(map[int]bool)
+func (iterator *ITaxon) IFilterOnName(name string, strict bool) *ITaxon {
+	newIterator := NewITaxon()
+	sentTaxa := make(map[*string]bool)
 
 	if strict {
 		go func() {
 			for iterator.Next() {
 				taxon := iterator.Get()
-				if _, ok := sentTaxa[taxon.taxid]; !ok {
+				node := taxon.Node
+				if _, ok := sentTaxa[node.id]; !ok {
 					if taxon.IsNameEqual(name) {
-						sentTaxa[taxon.taxid] = true
+						sentTaxa[node.id] = true
 						newIterator.source <- taxon
 					}
 				}
@@ -41,9 +42,10 @@ func (iterator *ITaxonSet) IFilterOnName(name string, strict bool) *ITaxonSet {
 		go func() {
 			for iterator.Next() {
 				taxon := iterator.Get()
-				if _, ok := sentTaxa[taxon.taxid]; !ok {
+				node := taxon.Node
+				if _, ok := sentTaxa[node.id]; !ok {
 					if taxon.IsNameMatching(pattern) {
-						sentTaxa[taxon.taxid] = true
+						sentTaxa[node.id] = true
 						newIterator.source <- taxon
 					}
 				}
diff --git a/pkg/obitax/filter_on_rank.go b/pkg/obitax/filter_on_rank.go
index 8a1809f..08df40d 100644
--- a/pkg/obitax/filter_on_rank.go
+++ b/pkg/obitax/filter_on_rank.go
@@ -1,12 +1,20 @@
 package obitax
 
-func (iterator *ITaxonSet) IFilterOnTaxRank(rank string) *ITaxonSet {
-	newIter := NewITaxonSet()
+func (iterator *ITaxon) IFilterOnTaxRank(rank string) *ITaxon {
+	newIter := NewITaxon()
+	var prank *string
+	var ptax *Taxonomy
 
 	go func() {
 		for iterator.Next() {
+
 			taxon := iterator.Get()
-			if taxon.rank == rank {
+			if ptax != taxon.Taxonomy {
+				ptax = taxon.Taxonomy
+				prank = ptax.ranks.Innerize(rank)
+			}
+
+			if taxon.Node.rank == prank {
 				newIter.source <- taxon
 			}
 		}
@@ -16,14 +24,14 @@ func (iterator *ITaxonSet) IFilterOnTaxRank(rank string) *ITaxonSet {
 	return newIter
 }
 
-func (set *TaxonSet) IFilterOnTaxRank(rank string) *ITaxonSet {
+func (set *TaxonSet) IFilterOnTaxRank(rank string) *ITaxon {
 	return set.Iterator().IFilterOnTaxRank(rank)
 }
 
-func (slice *TaxonSlice) IFilterOnTaxRank(rank string) *ITaxonSet {
+func (slice *TaxonSlice) IFilterOnTaxRank(rank string) *ITaxon {
 	return slice.Iterator().IFilterOnTaxRank(rank)
 }
 
-func (taxonomy *Taxonomy) IFilterOnTaxRank(rank string) *ITaxonSet {
+func (taxonomy *Taxonomy) IFilterOnTaxRank(rank string) *ITaxon {
 	return taxonomy.Iterator().IFilterOnTaxRank(rank)
 }
diff --git a/pkg/obitax/filter_on_subclade_of.go b/pkg/obitax/filter_on_subclade_of.go
index 85268a1..0cb6883 100644
--- a/pkg/obitax/filter_on_subclade_of.go
+++ b/pkg/obitax/filter_on_subclade_of.go
@@ -1,9 +1,7 @@
 package obitax
 
-import "reflect"
-
-func (iterator *ITaxonSet) IFilterOnSubcladeOf(taxon *TaxNode) *ITaxonSet {
-	newIter := NewITaxonSet()
+func (iterator *ITaxon) IFilterOnSubcladeOf(taxon *Taxon) *ITaxon {
+	newIter := NewITaxon()
 
 	go func() {
 		for iterator.Next() {
@@ -18,32 +16,36 @@ func (iterator *ITaxonSet) IFilterOnSubcladeOf(taxon *TaxNode) *ITaxonSet {
 	return newIter
 }
 
-func (set *TaxonSet) IFilterOnSubcladeOf(taxon *TaxNode) *ITaxonSet {
+func (set *TaxonSet) IFilterOnSubcladeOf(taxon *Taxon) *ITaxon {
 	return set.Iterator().IFilterOnSubcladeOf(taxon)
 }
 
-func (slice *TaxonSlice) IFilterOnSubcladeOf(taxon *TaxNode) *ITaxonSet {
+func (slice *TaxonSlice) IFilterOnSubcladeOf(taxon *Taxon) *ITaxon {
 	return slice.Iterator().IFilterOnSubcladeOf(taxon)
 }
 
-func (taxonomy *Taxonomy) IFilterOnSubcladeOf(taxon *TaxNode) *ITaxonSet {
+func (taxonomy *Taxonomy) IFilterOnSubcladeOf(taxon *Taxon) *ITaxon {
 	return taxonomy.Iterator().IFilterOnSubcladeOf(taxon)
 }
 
-func (iterator *ITaxonSet) IFilterBelongingSubclades(clades *TaxonSet) *ITaxonSet {
+func (iterator *ITaxon) IFilterBelongingSubclades(clades *TaxonSet) *ITaxon {
 
-	if len(*clades) == 0 {
+	if clades.Len() == 0 {
 		return iterator
 	}
 
 	// Considers the second simplest case when only
 	// a single subclase is provided
-	if len(*clades) == 1 {
-		keys := reflect.ValueOf(*clades).MapKeys()
-		return iterator.IFilterOnSubcladeOf((*clades)[int(keys[0].Int())])
+	if clades.Len() == 1 {
+		keys := make([]*string, 0, len(clades.set))
+		for k := range clades.set {
+			keys = append(keys, k)
+		}
+
+		return iterator.IFilterOnSubcladeOf(clades.Get(keys[0]))
 	}
 
-	newIter := NewITaxonSet()
+	newIter := NewITaxon()
 
 	go func() {
 		for iterator.Next() {
diff --git a/pkg/obitax/inner.go b/pkg/obitax/inner.go
index 3a248f2..8053f13 100644
--- a/pkg/obitax/inner.go
+++ b/pkg/obitax/inner.go
@@ -5,7 +5,7 @@ import "sync"
 // InnerString is a struct that holds a map of strings and a read-write lock for concurrent access.
 // The index map is used to store key-value pairs of strings.
 type InnerString struct {
-	index map[string]string
+	index map[string]*string
 	lock  sync.RWMutex
 }
 
@@ -13,7 +13,7 @@ type InnerString struct {
 // The lock is set to false.
 func NewInnerString() *InnerString {
 	return &InnerString{
-		index: make(map[string]string),
+		index: make(map[string]*string),
 	}
 }
 
@@ -26,13 +26,13 @@ func NewInnerString() *InnerString {
 //
 // Returns:
 //   - The string value associated with the key.
-func (i *InnerString) Innerize(value string) string {
+func (i *InnerString) Innerize(value string) *string {
 	i.lock.Lock()
 	defer i.lock.Unlock()
 	s, ok := i.index[value]
 	if !ok {
-		i.index[value] = value
-		s = value
+		s = &value
+		i.index[value] = s
 	}
 
 	return s
@@ -42,7 +42,7 @@ func (i *InnerString) Slice() []string {
 	rep := make([]string, len(i.index))
 	j := 0
 	for _, v := range i.index {
-		rep[j] = v
+		rep[j] = *v
 		j++
 	}
 	return rep
diff --git a/pkg/obitax/issuubcladeof.go b/pkg/obitax/issuubcladeof.go
index 82a08ae..50d186f 100644
--- a/pkg/obitax/issuubcladeof.go
+++ b/pkg/obitax/issuubcladeof.go
@@ -1,6 +1,6 @@
 package obitax
 
-import "log"
+import log "github.com/sirupsen/logrus"
 
 func (taxon *Taxon) IsSubCladeOf(parent *Taxon) bool {
 
@@ -20,3 +20,18 @@ func (taxon *Taxon) IsSubCladeOf(parent *Taxon) bool {
 
 	return false
 }
+
+func (taxon *Taxon) IsBelongingSubclades(clades *TaxonSet) bool {
+	ok := clades.Contains(taxon.Node.id)
+
+	for !ok && !taxon.IsRoot() {
+		taxon = taxon.Parent()
+		ok = clades.Contains(taxon.Node.id)
+	}
+
+	if taxon.IsRoot() {
+		ok = clades.Contains(taxon.Node.id)
+	}
+
+	return ok
+}
diff --git a/pkg/obitax/iterator.go b/pkg/obitax/iterator.go
index 5c29834..2b6568d 100644
--- a/pkg/obitax/iterator.go
+++ b/pkg/obitax/iterator.go
@@ -1,24 +1,31 @@
 package obitax
 
-type ITaxonSet struct {
-	source     chan *TaxNode
-	current    *TaxNode
+type ITaxon struct {
+	source     chan *Taxon
+	current    *Taxon
 	finished   bool
 	p_finished *bool
 }
 
-func NewITaxonSet() *ITaxonSet {
-	i := ITaxonSet{make(chan *TaxNode), nil, false, nil}
+func NewITaxon() *ITaxon {
+	i := ITaxon{
+		source:     make(chan *Taxon),
+		current:    nil,
+		finished:   false,
+		p_finished: nil}
 	i.p_finished = &i.finished
 	return &i
 }
 
-func (set *TaxonSet) Iterator() *ITaxonSet {
-	i := NewITaxonSet()
+func (set *TaxonSet) Iterator() *ITaxon {
+	i := NewITaxon()
 
 	go func() {
 		for _, t := range set.set {
-			i.source <- t
+			i.source <- &Taxon{
+				Taxonomy: set.taxonomy,
+				Node:     t,
+			}
 		}
 		close(i.source)
 	}()
@@ -26,12 +33,15 @@ func (set *TaxonSet) Iterator() *ITaxonSet {
 	return i
 }
 
-func (set *TaxonSlice) Iterator() *ITaxonSet {
-	i := NewITaxonSet()
+func (set *TaxonSlice) Iterator() *ITaxon {
+	i := NewITaxon()
 
 	go func() {
 		for _, t := range set.slice {
-			i.source <- t
+			i.source <- &Taxon{
+				Taxonomy: set.taxonomy,
+				Node:     t,
+			}
 		}
 		close(i.source)
 	}()
@@ -39,11 +49,11 @@ func (set *TaxonSlice) Iterator() *ITaxonSet {
 	return i
 }
 
-func (taxonmy *Taxonomy) Iterator() *ITaxonSet {
+func (taxonmy *Taxonomy) Iterator() *ITaxon {
 	return taxonmy.nodes.Iterator()
 }
 
-func (iterator *ITaxonSet) Next() bool {
+func (iterator *ITaxon) Next() bool {
 	if *(iterator.p_finished) {
 		return false
 	}
@@ -63,37 +73,21 @@ func (iterator *ITaxonSet) Next() bool {
 // currently pointed by the iterator. You have to use the
 // 'Next' method to move to the next entry before calling
 // 'Get' to retreive the following instance.
-func (iterator *ITaxonSet) Get() *TaxNode {
+func (iterator *ITaxon) Get() *Taxon {
 	return iterator.current
 }
 
 // Finished returns 'true' value if no more data is available
 // from the iterator.
-func (iterator *ITaxonSet) Finished() bool {
+func (iterator *ITaxon) Finished() bool {
 	return *iterator.p_finished
 }
 
-func (iterator *ITaxonSet) Split() *ITaxonSet {
-	newIter := ITaxonSet{iterator.source, nil, false, iterator.p_finished}
-	return &newIter
-}
-
-func (iterator *ITaxonSet) TaxonSet() *TaxonSet {
-	set := make(TaxonSet)
-
-	for iterator.Next() {
-		taxon := iterator.Get()
-		set[taxon.id] = taxon
+func (iterator *ITaxon) Split() *ITaxon {
+	return &ITaxon{
+		source:     iterator.source,
+		current:    nil,
+		finished:   false,
+		p_finished: iterator.p_finished,
 	}
-	return &set
-}
-
-func (iterator *ITaxonSet) TaxonSlice() *TaxonSlice {
-	slice := make(TaxonSlice, 0)
-
-	for iterator.Next() {
-		taxon := iterator.Get()
-		slice = append(slice, taxon)
-	}
-	return &slice
 }
diff --git a/pkg/obitax/lca.go b/pkg/obitax/lca.go
index 2b080ad..4909847 100644
--- a/pkg/obitax/lca.go
+++ b/pkg/obitax/lca.go
@@ -4,7 +4,7 @@ import (
 	log "github.com/sirupsen/logrus"
 )
 
-func (t1 *TaxNode) LCA(t2 *TaxNode) (*TaxNode, error) {
+func (t1 *Taxon) LCA(t2 *Taxon) (*Taxon, error) {
 	if t1 == nil {
 		log.Panicf("Try to get LCA of nil taxon")
 	}
@@ -13,25 +13,19 @@ func (t1 *TaxNode) LCA(t2 *TaxNode) (*TaxNode, error) {
 		log.Panicf("Try to get LCA of nil taxon")
 	}
 
-	p1, err1 := t1.Path()
+	p1 := t1.Path()
+	p2 := t2.Path()
 
-	if err1 != nil {
-		return nil, err1
-	}
+	i1 := p1.Len() - 1
+	i2 := p2.Len() - 1
 
-	p2, err2 := t2.Path()
-
-	if err2 != nil {
-		return nil, err2
-	}
-
-	i1 := len(*p1) - 1
-	i2 := len(*p2) - 1
-
-	for i1 >= 0 && i2 >= 0 && (*p1)[i1].taxid == (*p2)[i2].taxid {
+	for i1 >= 0 && i2 >= 0 && p1.slice[i1].id == p2.slice[i2].id {
 		i1--
 		i2--
 	}
 
-	return (*p1)[i1+1], nil
+	return &Taxon{
+		Taxonomy: t1.Taxonomy,
+		Node:     p1.slice[i1+1],
+	}, nil
 }
diff --git a/pkg/obitax/taxon.go b/pkg/obitax/taxon.go
index 74c9a99..09401d5 100644
--- a/pkg/obitax/taxon.go
+++ b/pkg/obitax/taxon.go
@@ -24,6 +24,9 @@ type Taxon struct {
 // Returns:
 //   - A formatted string representing the Taxon in the form "taxonomy_code:taxon_id [scientific_name]".
 func (taxon *Taxon) String() string {
+	if taxon == nil {
+		return "NA"
+	}
 	return taxon.Node.String(taxon.Taxonomy.code)
 }
 
@@ -33,24 +36,52 @@ func (taxon *Taxon) String() string {
 // Returns:
 //   - The scientific name of the taxon as a string.
 func (taxon *Taxon) ScientificName() string {
+	if taxon == nil {
+		return "NA"
+	}
 	return taxon.Node.ScientificName()
 }
 
 func (taxon *Taxon) Name(class string) string {
-	return taxon.Node.Name(class)
+	if taxon == nil {
+		return "NA"
+	}
+	pclass := taxon.Taxonomy.nameclasses.Innerize(class)
+	return taxon.Node.Name(pclass)
 }
 
 func (taxon *Taxon) IsNameEqual(name string) bool {
+	if taxon == nil {
+		return false
+	}
+
 	return taxon.Node.IsNameEqual(name)
 }
 
 func (taxon *Taxon) IsNameMatching(pattern *regexp.Regexp) bool {
+	if taxon == nil {
+		return false
+	}
+
 	return taxon.Node.IsNameMatching(pattern)
 }
 
 func (taxon *Taxon) SetName(name, class string) {
-	class = taxon.Taxonomy.nameclasses.Innerize(class)
-	taxon.Node.SetName(name, class)
+	if taxon == nil {
+		log.Panicf("nil taxon pointer for name %s [%s]", name, class)
+	}
+
+	pclass := taxon.Taxonomy.nameclasses.Innerize(class)
+	pname := taxon.Taxonomy.names.Innerize(name)
+	taxon.Node.SetName(pname, pclass)
+}
+
+func (taxon *Taxon) IsRoot() bool {
+	if taxon == nil {
+		return true
+	}
+
+	return taxon.Taxonomy.root == taxon.Node
 }
 
 // Rank returns the rank of the Taxon.
@@ -59,6 +90,9 @@ func (taxon *Taxon) SetName(name, class string) {
 // Returns:
 //   - The rank of the taxon as a string (e.g., species, genus, family).
 func (taxon *Taxon) Rank() string {
+	if taxon == nil {
+		return "NA"
+	}
 	return taxon.Node.Rank()
 }
 
@@ -70,9 +104,12 @@ func (taxon *Taxon) Rank() string {
 //   - A pointer to the parent Taxon[T]. If the parent does not exist, it returns
 //     a Taxon with a nil Node.
 func (taxon *Taxon) Parent() *Taxon {
+	if taxon == nil {
+		return nil
+	}
+
 	pid := taxon.Node.ParentId()
-	return &Taxon{taxon.Taxonomy,
-		taxon.Taxonomy.nodes.Get(pid)}
+	return taxon.Taxonomy.nodes.Get(pid)
 }
 
 // IPath returns an iterator that yields the path from the current Taxon to the root Taxon
@@ -83,12 +120,13 @@ func (taxon *Taxon) Parent() *Taxon {
 //     is called with each Taxon in the path from the current taxon to the root. If the
 //     taxonomy has no root node, the method logs a fatal error and terminates the program.
 func (taxon *Taxon) IPath() iter.Seq[*Taxon] {
+
 	if taxon.Taxonomy.root == nil {
 		log.Fatalf("Taxon[%v].IPath(): Taxonomy has no root node", taxon.Taxonomy.name)
 	}
 
 	return func(yield func(*Taxon) bool) {
-		for taxon.Node.parent != taxon.Taxonomy.root.id {
+		for !taxon.IsRoot() {
 			if !yield(taxon) {
 				return
 			}
@@ -96,8 +134,9 @@ func (taxon *Taxon) IPath() iter.Seq[*Taxon] {
 			taxon = taxon.Parent()
 		}
 
-		yield(taxon)
-
+		if taxon != nil {
+			yield(taxon)
+		}
 	}
 }
 
@@ -109,6 +148,10 @@ func (taxon *Taxon) IPath() iter.Seq[*Taxon] {
 //   - A pointer to a TaxonSlice[T] containing the TaxNode[T] instances in the path
 //     from the current taxon to the root.
 func (taxon *Taxon) Path() *TaxonSlice {
+	if taxon == nil {
+		return nil
+	}
+
 	s := make([]*TaxNode, 0, 10)
 
 	for t := range taxon.IPath() {
@@ -131,8 +174,13 @@ func (taxon *Taxon) Path() *TaxonSlice {
 // Returns:
 //   - A boolean indicating whether any taxon in the path has the specified rank defined.
 func (taxon *Taxon) HasRankDefined(rank string) bool {
+	if taxon == nil {
+		return false
+	}
+
+	prank := taxon.Taxonomy.ranks.Innerize(rank)
 	for t := range taxon.IPath() {
-		if t.Node.Rank() == rank {
+		if t.Node.rank == prank {
 			return true
 		}
 	}
@@ -151,8 +199,14 @@ func (taxon *Taxon) HasRankDefined(rank string) bool {
 //   - A pointer to the Taxon[T] that matches the specified rank, or nil if no such taxon exists
 //     in the path to the root.
 func (taxon *Taxon) TaxonAtRank(rank string) *Taxon {
+	if taxon == nil {
+		return nil
+	}
+
+	prank := taxon.Taxonomy.ranks.Innerize(rank)
+
 	for t := range taxon.IPath() {
-		if t.Node.Rank() == rank {
+		if t.Node.rank == prank {
 			return t
 		}
 	}
diff --git a/pkg/obitax/taxonnode.go b/pkg/obitax/taxonnode.go
index 3c12a50..f5f67fc 100644
--- a/pkg/obitax/taxonnode.go
+++ b/pkg/obitax/taxonnode.go
@@ -2,6 +2,7 @@ package obitax
 
 import (
 	"fmt"
+	"log"
 	"regexp"
 )
 
@@ -18,11 +19,11 @@ import (
 //     a string representing the class name and the value is a pointer to a string
 //     representing the name.
 type TaxNode struct {
-	id             string
-	parent         string
-	rank           string
+	id             *string
+	parent         *string
+	rank           *string
 	scientificname *string
-	alternatenames *map[string]*string
+	alternatenames *map[*string]*string
 }
 
 // String returns a string representation of the TaxNode, including the taxonomy code,
@@ -36,7 +37,7 @@ type TaxNode struct {
 func (node *TaxNode) String(taxonomyCode string) string {
 	return fmt.Sprintf("%s:%v [%s]",
 		taxonomyCode,
-		node.id,
+		*node.id,
 		node.ScientificName())
 }
 
@@ -45,7 +46,7 @@ func (node *TaxNode) String(taxonomyCode string) string {
 //
 // Returns:
 //   - The unique identifier of the taxon node of type T.
-func (node *TaxNode) Id() string {
+func (node *TaxNode) Id() *string {
 	return node.id
 }
 
@@ -54,7 +55,7 @@ func (node *TaxNode) Id() string {
 //
 // Returns:
 //   - The identifier of the parent taxon of type T.
-func (node *TaxNode) ParentId() string {
+func (node *TaxNode) ParentId() *string {
 	return node.parent
 }
 
@@ -66,6 +67,12 @@ func (node *TaxNode) ParentId() string {
 //   - Note: This method assumes that scientificname is not nil;
 //     if it may be nil, additional error handling should be implemented.
 func (node *TaxNode) ScientificName() string {
+	if node == nil {
+		return "NA"
+	}
+	if node.scientificname == nil {
+		return "NA"
+	}
 	return *node.scientificname
 }
 
@@ -80,8 +87,9 @@ func (node *TaxNode) ScientificName() string {
 // Returns:
 //   - The name of the taxon as a string. If the class is not recognized or if no name is available,
 //     an empty string is returned.
-func (node *TaxNode) Name(class string) string {
-	if class == "scientificname" {
+func (node *TaxNode) Name(class *string) string {
+
+	if *class == "scientific name" {
 		return *node.scientificname
 	}
 
@@ -98,17 +106,21 @@ func (node *TaxNode) Name(class string) string {
 	return ""
 }
 
-func (node *TaxNode) SetName(name, class string) {
-	if class == "scientificname" {
-		node.scientificname = &name
+func (node *TaxNode) SetName(name, class *string) {
+	if node == nil {
+		log.Panic("Cannot set name of nil TaxNode")
+	}
+
+	if *class == "scientific name" {
+		node.scientificname = name
 		return
 	}
 
 	if node.alternatenames == nil {
-		node.alternatenames = &map[string]*string{}
+		node.alternatenames = &map[*string]*string{}
 	}
 
-	(*node.alternatenames)[class] = &name
+	(*node.alternatenames)[class] = name
 }
 
 // Rank returns the rank of the TaxNode.
@@ -117,7 +129,7 @@ func (node *TaxNode) SetName(name, class string) {
 // Returns:
 //   - The rank of the taxon as a string (e.g., species, genus, family).
 func (node *TaxNode) Rank() string {
-	return node.rank
+	return *node.rank
 }
 
 // IsNameEqual checks if the provided name matches the scientific name or any alternate names
@@ -154,9 +166,14 @@ func (node *TaxNode) IsNameEqual(name string) bool {
 //   - A boolean indicating whether the scientific name or any alternate names match the
 //     provided regular expression pattern.
 func (node *TaxNode) IsNameMatching(pattern *regexp.Regexp) bool {
-	if pattern.MatchString(*(node.scientificname)) {
+	if node == nil {
+		return false
+	}
+
+	if node.scientificname != nil && pattern.MatchString(*(node.scientificname)) {
 		return true
 	}
+
 	if node.alternatenames != nil {
 		for _, n := range *node.alternatenames {
 			if n != nil && pattern.MatchString(*n) {
diff --git a/pkg/obitax/taxonomy.go b/pkg/obitax/taxonomy.go
index 47c0fdb..2f84334 100644
--- a/pkg/obitax/taxonomy.go
+++ b/pkg/obitax/taxonomy.go
@@ -21,12 +21,14 @@ import (
 type Taxonomy struct {
 	name        string
 	code        string
+	ids         *InnerString
 	ranks       *InnerString
 	nameclasses *InnerString
+	names       *InnerString
 	nodes       *TaxonSet
 	root        *TaxNode
 	matcher     *regexp.Regexp
-	index       map[string]*TaxonSet
+	index       map[*string]*TaxonSet
 }
 
 // NewTaxonomy creates and initializes a new Taxonomy instance with the specified name and code.
@@ -39,7 +41,7 @@ type Taxonomy struct {
 // Returns:
 //   - A pointer to the newly created Taxonomy instance.
 func NewTaxonomy(name, code, codeCharacters string) *Taxonomy {
-	set := make(map[string]*TaxNode)
+	set := make(map[*string]*TaxNode)
 
 	// 	codeCharacters := "[[:alnum:]]" // [[:digit:]]
 
@@ -48,12 +50,14 @@ func NewTaxonomy(name, code, codeCharacters string) *Taxonomy {
 	taxonomy := &Taxonomy{
 		name:        name,
 		code:        code,
+		ids:         NewInnerString(),
 		ranks:       NewInnerString(),
 		nameclasses: NewInnerString(),
+		names:       NewInnerString(),
 		nodes:       &TaxonSet{set: set},
 		root:        nil,
 		matcher:     matcher,
-		index:       make(map[string]*TaxonSet),
+		index:       make(map[*string]*TaxonSet),
 	}
 
 	taxonomy.nodes.taxonomy = taxonomy
@@ -69,16 +73,16 @@ func NewTaxonomy(name, code, codeCharacters string) *Taxonomy {
 //   - taxid: A string representation of the taxon identifier to be converted.
 //
 // Returns:
-//   - The taxon identifier of type T corresponding to the provided taxid.
+//   - The taxon identifier as a *string corresponding to the provided taxid.
 //   - An error if the taxid is not valid or cannot be converted.
-func (taxonomy *Taxonomy) Id(taxid string) (string, error) {
+func (taxonomy *Taxonomy) Id(taxid string) (*string, error) {
 	matches := taxonomy.matcher.FindStringSubmatch(taxid)
 
 	if matches == nil {
-		return "", fmt.Errorf("Taxid %s is not a valid taxid", taxid)
+		return nil, fmt.Errorf("taxid %s is not a valid taxid", taxid)
 	}
 
-	return matches[2], nil
+	return taxonomy.ids.Innerize(matches[2]), nil
 }
 
 // TaxidSting retrieves the string representation of a taxon node identified by the given ID.
@@ -92,11 +96,19 @@ func (taxonomy *Taxonomy) Id(taxid string) (string, error) {
 //   - A string representing the taxon node in the format "taxonomyCode:id [scientificName]",
 //     or an error if the taxon node with the specified ID does not exist in the taxonomy.
 func (taxonomy *Taxonomy) TaxidSting(id string) (string, error) {
-	node := taxonomy.nodes.Get(id)
-	if node == nil {
-		return "", fmt.Errorf("Taxid %d is part of the taxonomy", id)
+	pid, err := taxonomy.Id(id)
+
+	if err != nil {
+		return "", err
 	}
-	return node.String(taxonomy.code), nil
+
+	taxon := taxonomy.nodes.Get(pid)
+
+	if taxon == nil {
+		return "", fmt.Errorf("taxid %s is not part of the taxonomy", id)
+	}
+
+	return taxon.String(), nil
 }
 
 // Taxon retrieves the Taxon associated with the given taxid string.
@@ -113,19 +125,18 @@ func (taxonomy *Taxonomy) Taxon(taxid string) *Taxon {
 	id, err := taxonomy.Id(taxid)
 
 	if err != nil {
-		log.Fatalf("Taxid %s is not a valid taxid", taxid)
+		log.Fatalf("Taxid %s: %v", taxid, err)
 	}
 
-	node := taxonomy.nodes.Get(id)
+	taxon := taxonomy.nodes.Get(id)
 
-	if node == nil {
-		log.Fatalf("Taxid %s is an unknown taxid", taxid)
+	if taxon == nil {
+		log.Fatalf("Taxid %s is not part of the taxonomy %s",
+			taxid,
+			taxonomy.name)
 	}
 
-	return &Taxon{
-		Taxonomy: taxonomy,
-		Node:     node,
-	}
+	return taxon
 }
 
 // TaxonSet returns the set of taxon nodes contained within the Taxonomy.
@@ -133,7 +144,7 @@ func (taxonomy *Taxonomy) Taxon(taxid string) *Taxon {
 //
 // Returns:
 //   - A pointer to the TaxonSet[T] representing the collection of taxon nodes in the taxonomy.
-func (taxonomy *Taxonomy) TaxonSet() *TaxonSet {
+func (taxonomy *Taxonomy) AsTaxonSet() *TaxonSet {
 	return taxonomy.nodes
 }
 
@@ -160,13 +171,25 @@ func (taxonomy *Taxonomy) Len() int {
 //   - A pointer to the newly created Taxon[T] instance.
 //   - An error if the taxon cannot be added (e.g., it already exists and replace is false).
 func (taxonomy *Taxonomy) AddTaxon(taxid, parent string, rank string, isRoot bool, replace bool) (*Taxon, error) {
-	if !replace && taxonomy.nodes.Contains(taxid) {
-		return nil, fmt.Errorf("trying to add taxon %d already present in the taxonomy", taxid)
+
+	parentid, perr := taxonomy.Id(parent)
+	id, err := taxonomy.Id(taxid)
+
+	if perr != nil {
+		return nil, fmt.Errorf("error in parsing parent taxid %s: %v", parent, perr)
 	}
 
-	rank = taxonomy.ranks.Innerize(rank)
+	if err != nil {
+		return nil, fmt.Errorf("error in parsing taxid %s: %v", taxid, err)
+	}
 
-	n := &TaxNode{taxid, parent, rank, nil, nil}
+	if !replace && taxonomy.nodes.Contains(id) {
+		return nil, fmt.Errorf("trying to add taxon %s already present in the taxonomy", taxid)
+	}
+
+	prank := taxonomy.ranks.Innerize(rank)
+
+	n := &TaxNode{id, parentid, prank, nil, nil}
 
 	taxonomy.nodes.Insert(n)
 
@@ -197,18 +220,15 @@ func (taxonomy *Taxonomy) AddAlias(newtaxid, oldtaxid string, replace bool) (*Ta
 		return nil, fmt.Errorf("trying to add alias %s already present in the taxonomy", newtaxid)
 	}
 
-	n := taxonomy.nodes.Get(oldid)
+	t := taxonomy.nodes.Get(oldid)
 
-	if n == nil {
+	if t == nil {
 		return nil, fmt.Errorf("trying to add alias %s to a taxon that does not exist", oldtaxid)
 	}
 
-	taxonomy.nodes.Alias(newid, n)
+	taxonomy.nodes.Alias(newid, t)
 
-	return &Taxon{
-		Taxonomy: taxonomy,
-		Node:     n,
-	}, nil
+	return t, nil
 }
 
 // RankList returns a slice of strings representing the ranks of the taxa
@@ -221,19 +241,14 @@ func (taxonomy *Taxonomy) RankList() []string {
 	return taxonomy.ranks.Slice()
 }
 
-// func (taxonomy *Taxonomy) Taxon(taxid int) (*TaxNode, error) {
-// 	t, ok := (*taxonomy.nodes)[taxid]
-
-// 	if !ok {
-// 		a, aok := taxonomy.alias[taxid]
-// 		if !aok {
-// 			return nil, fmt.Errorf("Taxid %d is not part of the taxonomy", taxid)
-// 		}
-// 		t = a
-// 	}
-// 	return t, nil
-// }
-
-func (taxonomy *Taxonomy) Index() *map[string]*TaxonSet {
+func (taxonomy *Taxonomy) Index() *map[*string]*TaxonSet {
 	return &(taxonomy.index)
 }
+
+func (taxonomy *Taxonomy) Name() string {
+	return taxonomy.name
+}
+
+func (taxonomy *Taxonomy) Code() string {
+	return taxonomy.code
+}
diff --git a/pkg/obitax/taxonset.go b/pkg/obitax/taxonset.go
index 3f464e1..3d690ef 100644
--- a/pkg/obitax/taxonset.go
+++ b/pkg/obitax/taxonset.go
@@ -1,3 +1,4 @@
+// Package obitax provides functionality for managing taxonomic data structures.
 package obitax
 
 import log "github.com/sirupsen/logrus"
@@ -7,25 +8,46 @@ import log "github.com/sirupsen/logrus"
 // as well as a reference to the associated Taxonomy.
 //
 // Fields:
-//   - set: A map that associates taxon identifiers of type T with their corresponding TaxNode[T] instances.
-//   - taxonomy: A pointer to the Taxonomy[T] instance that this TaxonSet belongs to.
+//   - set: A map that associates taxon identifiers of type *string with their corresponding TaxNode instances.
+//   - nalias: The number of aliases in the TaxonSet.
+//   - taxonomy: A pointer to the Taxonomy instance that this TaxonSet belongs to.
 type TaxonSet struct {
-	set      map[string]*TaxNode
+	set      map[*string]*TaxNode
 	nalias   int
 	taxonomy *Taxonomy
 }
 
-// Get retrieves the TaxNode[T] associated with the specified taxon identifier.
+func (taxonomy *Taxonomy) NewTaxonSet() *TaxonSet {
+	return &TaxonSet{
+		set:      make(map[*string]*TaxNode),
+		nalias:   0,
+		taxonomy: taxonomy,
+	}
+}
+
+// Get retrieves the TaxNode associated with the specified taxon identifier.
 // It returns the TaxNode if it exists in the TaxonSet; otherwise, it returns nil.
 //
 // Parameters:
-//   - i: The taxon identifier of type T for which the TaxNode is to be retrieved.
+//   - id: A pointer to the taxon identifier for which the TaxNode is to be retrieved.
 //
 // Returns:
-//   - A pointer to the TaxNode[T] associated with the provided identifier, or nil
+//   - A pointer to the TaxNode associated with the provided identifier, or nil
 //     if no such taxon exists in the set.
-func (set *TaxonSet) Get(i string) *TaxNode {
-	return set.set[i]
+func (set *TaxonSet) Get(id *string) *Taxon {
+	if set == nil {
+		return nil
+	}
+
+	node := set.set[id]
+	if node == nil {
+		return nil
+	}
+
+	return &Taxon{
+		Taxonomy: set.taxonomy,
+		Node:     set.set[id],
+	}
 }
 
 // Len returns the number of unique taxa in the TaxonSet.
@@ -38,27 +60,37 @@ func (set *TaxonSet) Len() int {
 	return len(set.set) - set.nalias
 }
 
-// Insert adds a TaxNode[T] to the TaxonSet. If a taxon with the same identifier
+// Insert adds a TaxNode to the TaxonSet. If a taxon with the same identifier
 // already exists in the set, it updates the reference. If the existing taxon was
 // an alias, its alias count is decremented.
 //
 // Parameters:
-//   - taxon: A pointer to the TaxNode[T] instance to be added to the TaxonSet.
+//   - taxon: A pointer to the TaxNode instance to be added to the TaxonSet.
 //
 // Behavior:
 //   - If a taxon with the same identifier already exists and is different from the
 //     new taxon, the alias count is decremented.
-func (set *TaxonSet) Insert(taxon *TaxNode) {
-	if old := set.set[taxon.id]; old != nil && old.id != taxon.id {
+func (set *TaxonSet) Insert(node *TaxNode) {
+	if old := set.set[node.id]; old != nil && old.id != node.id {
 		set.nalias--
 	}
-	set.set[taxon.id] = taxon
+	set.set[node.id] = node
 }
 
-// Taxonomy returns a pointer to the Taxonomy[T] instance that this TaxonSet belongs to.
+func (set *TaxonSet) InsertTaxon(taxon *Taxon) {
+	if set.taxonomy != taxon.Taxonomy {
+		log.Fatalf(
+			"Cannot insert taxon %s into taxon set belonging %s taxonomy",
+			taxon.String(),
+			set.taxonomy.name,
+		)
+	}
+}
+
+// Taxonomy returns a pointer to the Taxonomy instance that this TaxonSet belongs to.
 //
 // Returns:
-//   - A pointer to the Taxonomy[T] instance that this TaxonSet belongs to
+//   - A pointer to the Taxonomy instance that this TaxonSet belongs to.
 func (set *TaxonSet) Taxonomy() *Taxonomy {
 	return set.taxonomy
 }
@@ -68,18 +100,18 @@ func (set *TaxonSet) Taxonomy() *Taxonomy {
 // If the original taxon is not part of the taxon set, it logs a fatal error and terminates the program.
 //
 // Parameters:
-//   - alias: A string representing the alias to be associated with the taxon node.
-//   - node: A pointer to the TaxNode[T] instance that the alias will refer to.
+//   - alias: A pointer to a string representing the alias to be associated with the taxon node.
+//   - node: A pointer to the TaxNode instance that the alias will refer to.
 //
 // Behavior:
 //   - If the original taxon corresponding to the alias is not part of the taxon set,
 //     the method will log a fatal error and terminate the program.
-func (set *TaxonSet) Alias(id string, node *TaxNode) {
-	original := set.Get(node.id)
-	if original != nil {
+func (set *TaxonSet) Alias(id *string, taxon *Taxon) {
+	original := set.Get(taxon.Node.id)
+	if original == nil {
 		log.Fatalf("Original taxon %v is not part of taxon set", id)
 	}
-	set.set[id] = node
+	set.set[id] = taxon.Node
 	set.nalias++
 }
 
@@ -88,39 +120,39 @@ func (set *TaxonSet) Alias(id string, node *TaxNode) {
 // node exists and its identifier is different from the provided identifier; otherwise, it returns false.
 //
 // Parameters:
-//   - id: The identifier of type T to be checked for alias status.
+//   - id: A pointer to the identifier to be checked for alias status.
 //
 // Returns:
 //   - A boolean indicating whether the identifier corresponds to an alias in the set.
-func (set *TaxonSet) IsAlias(id string) bool {
-	node := set.Get(id)
-	return node != nil && node.id != id
+func (set *TaxonSet) IsAlias(id *string) bool {
+	taxon := set.Get(id)
+	return taxon != nil && taxon.Node.id != id
 }
 
 // IsATaxon checks if the given ID corresponds to a valid taxon node in the TaxonSet.
 // It returns true if the node exists and its ID matches the provided ID; otherwise, it returns false.
-// id corresponding to alias returns false.
+// If the ID corresponds to an alias, it will return false.
 //
 // Parameters:
-//   - id: The identifier of the taxon to check.
+//   - id: A pointer to the identifier of the taxon to check.
 //
 // Returns:
 //   - A boolean indicating whether the specified ID corresponds to a valid taxon node.
-func (set *TaxonSet) IsATaxon(id string) bool {
-	node := set.Get(id)
-	return node != nil && node.id == id
+func (set *TaxonSet) IsATaxon(id *string) bool {
+	taxon := set.Get(id)
+	return taxon != nil && taxon.Node.id == id
 }
 
 // Contains checks if the TaxonSet contains a taxon node with the specified ID.
 // It returns true if the node exists in the set; otherwise, it returns false.
-// id corresponding to alias or true taxa returns true.
+// If the ID corresponds to an alias, it will return true if the alias exists.
 //
 // Parameters:
-//   - id: The identifier of the taxon to check for presence in the set.
+//   - id: A pointer to the identifier of the taxon to check for presence in the set.
 //
 // Returns:
 //   - A boolean indicating whether the TaxonSet contains a taxon node with the specified ID.
-func (set *TaxonSet) Contains(id string) bool {
+func (set *TaxonSet) Contains(id *string) bool {
 	node := set.Get(id)
 	return node != nil
 }
diff --git a/pkg/obitax/taxonslice.go b/pkg/obitax/taxonslice.go
index 8c567d9..7acf119 100644
--- a/pkg/obitax/taxonslice.go
+++ b/pkg/obitax/taxonslice.go
@@ -3,6 +3,8 @@ package obitax
 import (
 	"bytes"
 	"fmt"
+
+	"git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obiutils"
 )
 
 // TaxonSlice represents a slice of TaxNode[T] instances within a taxonomy.
@@ -16,6 +18,13 @@ type TaxonSlice struct {
 	taxonomy *Taxonomy
 }
 
+func (taxonomy *Taxonomy) NewTaxonSlice(size, capacity int) *TaxonSlice {
+	return &TaxonSlice{
+		slice:    make([]*TaxNode, size, capacity),
+		taxonomy: taxonomy,
+	}
+}
+
 // Get retrieves the TaxNode[T] at the specified index from the TaxonSlice.
 // It returns the taxon node corresponding to the provided index.
 //
@@ -25,6 +34,9 @@ type TaxonSlice struct {
 // Returns:
 //   - A pointer to the TaxNode[T] at the specified index in the slice.
 func (slice *TaxonSlice) Get(i int) *TaxNode {
+	if slice == nil {
+		return nil
+	}
 	return slice.slice[i]
 }
 
@@ -34,6 +46,9 @@ func (slice *TaxonSlice) Get(i int) *TaxNode {
 // Returns:
 //   - An integer representing the total number of taxon nodes in the TaxonSlice.
 func (slice *TaxonSlice) Len() int {
+	if slice == nil {
+		return 0
+	}
 	return len(slice.slice)
 }
 
@@ -65,3 +80,19 @@ func (path *TaxonSlice) String() string {
 
 	return buffer.String()
 }
+
+func (slice *TaxonSlice) Reverse(inplace bool) *TaxonSlice {
+	if slice == nil {
+		return nil
+	}
+
+	rep := obiutils.Reverse(slice.slice, inplace)
+	if inplace {
+		return slice
+	}
+
+	return &TaxonSlice{
+		taxonomy: slice.taxonomy,
+		slice:    rep,
+	}
+}
diff --git a/pkg/obitools/obifind/iterator.go b/pkg/obitools/obifind/iterator.go
index 5884a2f..52e38af 100644
--- a/pkg/obitools/obifind/iterator.go
+++ b/pkg/obitools/obifind/iterator.go
@@ -7,13 +7,13 @@ import (
 	"git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obitax"
 )
 
-func IFilterRankRestriction() func(*obitax.ITaxonSet) *obitax.ITaxonSet {
-	f := func(s *obitax.ITaxonSet) *obitax.ITaxonSet {
+func IFilterRankRestriction() func(*obitax.ITaxon) *obitax.ITaxon {
+	f := func(s *obitax.ITaxon) *obitax.ITaxon {
 		return s
 	}
 
 	if __restrict_rank__ != "" {
-		f = func(s *obitax.ITaxonSet) *obitax.ITaxonSet {
+		f = func(s *obitax.ITaxon) *obitax.ITaxon {
 			return s.IFilterOnTaxRank(__restrict_rank__)
 		}
 	}
@@ -21,21 +21,21 @@ func IFilterRankRestriction() func(*obitax.ITaxonSet) *obitax.ITaxonSet {
 	return f
 }
 
-func ITaxonNameMatcher() (func(string) *obitax.ITaxonSet, error) {
+func ITaxonNameMatcher() (func(string) *obitax.ITaxon, error) {
 	taxonomy, err := CLILoadSelectedTaxonomy()
 
 	if err != nil {
 		return nil, err
 	}
 
-	fun := func(name string) *obitax.ITaxonSet {
+	fun := func(name string) *obitax.ITaxon {
 		return taxonomy.IFilterOnName(name, __fixed_pattern__)
 	}
 
 	return fun, nil
 }
 
-func ITaxonRestrictions() (func(*obitax.ITaxonSet) *obitax.ITaxonSet, error) {
+func ITaxonRestrictions() (func(*obitax.ITaxon) *obitax.ITaxon, error) {
 
 	clades, err := CLITaxonomicalRestrictions()
 
@@ -45,23 +45,19 @@ func ITaxonRestrictions() (func(*obitax.ITaxonSet) *obitax.ITaxonSet, error) {
 
 	rankfilter := IFilterRankRestriction()
 
-	fun := func(iterator *obitax.ITaxonSet) *obitax.ITaxonSet {
+	fun := func(iterator *obitax.ITaxon) *obitax.ITaxon {
 		return rankfilter(iterator).IFilterBelongingSubclades(clades)
 	}
 
 	return fun, nil
 }
 
-func TaxonAsString(taxon *obitax.TaxNode, pattern string) string {
+func TaxonAsString(taxon *obitax.Taxon, pattern string) string {
 	text := taxon.ScientificName()
 
 	if __with_path__ {
 		var bf bytes.Buffer
-		path, err := taxon.Path()
-
-		if err != nil {
-			fmt.Printf("%+v", err)
-		}
+		path := taxon.Path()
 
 		bf.WriteString(path.Get(path.Len() - 1).ScientificName())
 
@@ -72,15 +68,15 @@ func TaxonAsString(taxon *obitax.TaxNode, pattern string) string {
 		text = bf.String()
 	}
 
-	return fmt.Sprintf("%-20s | %10d | %10d | %-20s | %s",
+	return fmt.Sprintf("%-20s | %10s | %10s | %-20s | %s",
 		pattern,
-		taxon.Taxid(),
-		taxon.Parent().Taxid(),
+		taxon.String(),
+		taxon.Parent().String(),
 		taxon.Rank(),
 		text)
 }
 
-func TaxonWriter(itaxa *obitax.ITaxonSet, pattern string) {
+func TaxonWriter(itaxa *obitax.ITaxon, pattern string) {
 	for itaxa.Next() {
 		fmt.Println(TaxonAsString(itaxa.Get(), pattern))
 	}
diff --git a/pkg/obitools/obifind/options.go b/pkg/obitools/obifind/options.go
index 18f5a04..2533b23 100644
--- a/pkg/obitools/obifind/options.go
+++ b/pkg/obitools/obifind/options.go
@@ -12,12 +12,12 @@ var __taxdump__ = ""
 var __alternative_name__ = false
 var __rank_list__ = false
 var __selected_taxonomy__ = (*obitax.Taxonomy)(nil)
-var __taxonomical_restriction__ = make([]int, 0)
+var __taxonomical_restriction__ = make([]string, 0)
 
 var __fixed_pattern__ = false
 var __with_path__ = false
-var __taxid_path__ = -1
-var __taxid_sons__ = -1
+var __taxid_path__ = "NA"
+var __taxid_sons__ = "NA"
 var __restrict_rank__ = ""
 
 func LoadTaxonomyOptionSet(options *getoptions.GetOpt, required, alternatiive bool) {
@@ -43,7 +43,7 @@ func FilterTaxonomyOptionSet(options *getoptions.GetOpt) {
 		options.Alias("l"),
 		options.Description("List every taxonomic rank available in the taxonomy."))
 
-	options.IntSliceVar(&__taxonomical_restriction__, "restrict-to-taxon", 1, 1,
+	options.StringSliceVar(&__taxonomical_restriction__, "restrict-to-taxon", 1, 1,
 		options.Alias("r"),
 		options.Description("Restrict output to some subclades."))
 }
@@ -67,18 +67,18 @@ func CLITaxonomicalRestrictions() (*obitax.TaxonSet, error) {
 		return nil, err
 	}
 
-	ts := make(obitax.TaxonSet)
+	ts := taxonomy.NewTaxonSet()
 	for _, taxid := range __taxonomical_restriction__ {
-		tx, err := taxonomy.Taxon(taxid)
+		tx := taxonomy.Taxon(taxid)
 
 		if err != nil {
 			return nil, err
 		}
 
-		ts.Inserts(tx)
+		ts.InsertTaxon(tx)
 	}
 
-	return &ts, nil
+	return ts, nil
 }
 
 func CLILoadSelectedTaxonomy() (*obitax.Taxonomy, error) {
@@ -106,17 +106,17 @@ func OptionSet(options *getoptions.GetOpt) {
 	options.BoolVar(&__with_path__, "with-path", false,
 		options.Alias("P"),
 		options.Description("Adds a column containing the full path for each displayed taxon."))
-	options.IntVar(&__taxid_path__, "parents", -1,
+	options.StringVar(&__taxid_path__, "parents", "NA",
 		options.Alias("p"),
 		options.Description("Displays every parental tree's information for the provided taxid."))
 	options.StringVar(&__restrict_rank__, "rank", "",
 		options.Description("Restrict to the given taxonomic rank."))
 }
 
-func CLIRequestsPathForTaxid() int {
+func CLIRequestsPathForTaxid() string {
 	return __taxid_path__
 }
 
-func CLIRequestsSonsForTaxid() int {
+func CLIRequestsSonsForTaxid() string {
 	return __taxid_sons__
 }