diff --git a/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/sx/graph/bio/BioDBToOAF.scala b/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/sx/graph/bio/BioDBToOAF.scala
index a19c6fb12e..90b65c8f70 100644
--- a/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/sx/graph/bio/BioDBToOAF.scala
+++ b/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/sx/graph/bio/BioDBToOAF.scala
@@ -199,7 +199,7 @@ object BioDBToOAF {
         d.setDateofacceptance(OafMapperUtils.field(i_date.get.date, DATA_INFO))
       }
       val relevant_dates: List[StructuredProperty] = dates.filter(d => !d.date_info.contains("entry version"))
-        .map(date => OafMapperUtils.structuredProperty(date.date, "UNKNOWN", "UNKNOWN", ModelConstants.DNET_DATACITE_DATE, ModelConstants.DNET_DATACITE_DATE, DATA_INFO))
+        .map(date => OafMapperUtils.structuredProperty(date.date, ModelConstants.UNKNOWN, ModelConstants.UNKNOWN, ModelConstants.DNET_DATACITE_DATE, ModelConstants.DNET_DATACITE_DATE, DATA_INFO))
       if (relevant_dates != null && relevant_dates.nonEmpty)
         d.setRelevantdate(relevant_dates.asJava)
       d.setDateofacceptance(OafMapperUtils.field(i_date.get.date, DATA_INFO))
@@ -218,12 +218,12 @@ object BioDBToOAF {
 
 
     if (references_pmid != null && references_pmid.nonEmpty) {
-      val rel = createRelation(references_pmid.head, "pmid", d.getId, collectedFromMap("uniprot"), "relationship", "isRelatedTo", if  (i_date.isDefined) i_date.get.date else null)
+      val rel = createRelation(references_pmid.head, "pmid", d.getId, collectedFromMap("uniprot"), ModelConstants.RELATIONSHIP, ModelConstants.IS_RELATED_TO, if  (i_date.isDefined) i_date.get.date else null)
       rel.getCollectedfrom
       List(d, rel)
     }
     else if (references_doi != null && references_doi.nonEmpty) {
-      val rel = createRelation(references_doi.head, "doi", d.getId, collectedFromMap("uniprot"), "relationship", "isRelatedTo", if  (i_date.isDefined) i_date.get.date else null)
+      val rel = createRelation(references_doi.head, "doi", d.getId, collectedFromMap("uniprot"), ModelConstants.RELATIONSHIP, ModelConstants.IS_RELATED_TO, if  (i_date.isDefined) i_date.get.date else null)
       List(d, rel)
     }
     else
@@ -243,7 +243,7 @@ object BioDBToOAF {
     rel.setCollectedfrom(List(collectedFromMap("pdb")).asJava)
     rel.setDataInfo(DATA_INFO)
 
-    rel.setRelType("resultResult")
+    rel.setRelType(ModelConstants.RESULT_RESULT)
     rel.setSubRelType(subRelType)
     rel.setRelClass(relClass)
 
@@ -263,7 +263,7 @@ object BioDBToOAF {
 
 
   def createSupplementaryRelation(pid: String, pidType: String, sourceId: String, collectedFrom: KeyValue, date:String): Relation = {
-    createRelation(pid,pidType,sourceId,collectedFrom, "supplement","IsSupplementTo", date)
+    createRelation(pid,pidType,sourceId,collectedFrom, ModelConstants.SUPPLEMENT, ModelConstants.IS_SUPPLEMENT_TO, date)
   }
 
 
@@ -392,6 +392,6 @@ object BioDBToOAF {
     i.setDateofacceptance(OafMapperUtils.field(GraphCleaningFunctions.cleanDate(input.date), DATA_INFO))
     d.setDateofacceptance(OafMapperUtils.field(GraphCleaningFunctions.cleanDate(input.date), DATA_INFO))
 
-    List(d, createRelation(input.pmid, "pmid", d.getId, collectedFromMap("ebi"),"relationship", "isRelatedTo", GraphCleaningFunctions.cleanDate(input.date)))
+    List(d, createRelation(input.pmid, "pmid", d.getId, collectedFromMap("ebi"), ModelConstants.RELATIONSHIP, ModelConstants.IS_RELATED_TO, GraphCleaningFunctions.cleanDate(input.date)))
   }
 }
diff --git a/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/sx/graph/bio/pubmed/PubMedToOaf.scala b/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/sx/graph/bio/pubmed/PubMedToOaf.scala
index ae4a720626..9a49deebca 100644
--- a/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/sx/graph/bio/pubmed/PubMedToOaf.scala
+++ b/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/sx/graph/bio/pubmed/PubMedToOaf.scala
@@ -16,7 +16,7 @@ object PubMedToOaf {
   )
 
   def createResult(cobjQualifier: Qualifier, vocabularies: VocabularyGroup): Result = {
-    val result_typologies = getVocabularyTerm("dnet:result_typologies", vocabularies, cobjQualifier.getClassid)
+    val result_typologies = getVocabularyTerm(ModelConstants.DNET_RESULT_TYPOLOGIES, vocabularies, cobjQualifier.getClassid)
     result_typologies.getClassid match {
       case "dataset" => new Dataset
       case "publication" => new Publication
@@ -68,11 +68,11 @@ object PubMedToOaf {
     //else We have to find a terms that match the vocabulary otherwise we discard it
     val ja = article.getPublicationTypes.asScala.find(s => "Journal Article".equalsIgnoreCase(s.getValue))
     if (ja.isDefined) {
-      val cojbCategory = getVocabularyTerm("dnet:publication_resource", vocabularies, ja.get.getValue)
+      val cojbCategory = getVocabularyTerm(ModelConstants.DNET_PUBLICATION_RESOURCE, vocabularies, ja.get.getValue)
       i.setInstancetype(cojbCategory)
     } else {
       val i_type = article.getPublicationTypes.asScala
-        .map(s => getVocabularyTerm("dnet:publication_resource", vocabularies, s.getValue))
+        .map(s => getVocabularyTerm(ModelConstants.DNET_PUBLICATION_RESOURCE, vocabularies, s.getValue))
         .find(q => q != null)
       if (i_type.isDefined)
         i.setInstancetype(i_type.get)
@@ -112,7 +112,7 @@ object PubMedToOaf {
 
     if (article.getLanguage != null) {
 
-      val term = vocabularies.getSynonymAsQualifier("dnet:languages", article.getLanguage)
+      val term = vocabularies.getSynonymAsQualifier(ModelConstants.DNET_LANGUAGES, article.getLanguage)
       if (term != null)
         result.setLanguage(term)
     }