diff --git a/backend/api/admin.py b/backend/api/admin.py
index 22297bde..09c661e3 100644
--- a/backend/api/admin.py
+++ b/backend/api/admin.py
@@ -1,9 +1,8 @@
 from django.contrib import admin
 
-from .models import (Comment, Document, DocumentAnnotation, Label, Project,
-                     Role, RoleMapping, Seq2seqAnnotation, Seq2seqProject,
-                     SequenceAnnotation, SequenceLabelingProject, Tag,
-                     TextClassificationProject)
+from .models import (Category, Comment, Document, Label, Project, Role,
+                     RoleMapping, Seq2seqProject, SequenceLabelingProject,
+                     Span, Tag, TextClassificationProject, TextLabel)
 
 
 class LabelAdmin(admin.ModelAdmin):
@@ -24,22 +23,19 @@ class ProjectAdmin(admin.ModelAdmin):
     search_fields = ('name',)
 
 
-class SequenceAnnotationAdmin(admin.ModelAdmin):
-    list_display = ('document', 'label', 'start_offset', 'user')
-    ordering = ('document',)
-    search_fields = ('document__text',)
+class SpanAdmin(admin.ModelAdmin):
+    list_display = ('example', 'label', 'start_offset', 'user')
+    ordering = ('example',)
 
 
-class DocumentAnnotationAdmin(admin.ModelAdmin):
-    list_display = ('document', 'label', 'user')
-    ordering = ('document',)
-    search_fields = ('document__text',)
+class CategoryAdmin(admin.ModelAdmin):
+    list_display = ('example', 'label', 'user')
+    ordering = ('example',)
 
 
-class Seq2seqAnnotationAdmin(admin.ModelAdmin):
-    list_display = ('document', 'text', 'user')
-    ordering = ('document',)
-    search_fields = ('document__text',)
+class TextLabelAdmin(admin.ModelAdmin):
+    list_display = ('example', 'text', 'user')
+    ordering = ('example',)
 
 
 class RoleAdmin(admin.ModelAdmin):
@@ -66,9 +62,9 @@ class CommentAdmin(admin.ModelAdmin):
     search_fields = ('user',)
 
 
-admin.site.register(DocumentAnnotation, DocumentAnnotationAdmin)
-admin.site.register(SequenceAnnotation, SequenceAnnotationAdmin)
-admin.site.register(Seq2seqAnnotation, Seq2seqAnnotationAdmin)
+admin.site.register(Category, CategoryAdmin)
+admin.site.register(Span, SpanAdmin)
+admin.site.register(TextLabel, TextLabelAdmin)
 admin.site.register(Label, LabelAdmin)
 admin.site.register(Document, DocumentAdmin)
 admin.site.register(Project, ProjectAdmin)
diff --git a/backend/api/filters.py b/backend/api/filters.py
index c9e9dcf5..4e90b148 100644
--- a/backend/api/filters.py
+++ b/backend/api/filters.py
@@ -5,10 +5,9 @@ from .models import Document
 
 
 class DocumentFilter(FilterSet):
-    seq_annotations__isnull = BooleanFilter(field_name='seq_annotations', method='filter_annotations')
-    doc_annotations__isnull = BooleanFilter(field_name='doc_annotations', method='filter_annotations')
-    seq2seq_annotations__isnull = BooleanFilter(field_name='seq2seq_annotations', method='filter_annotations')
-    speech2text_annotations__isnull = BooleanFilter(field_name='speech2text_annotations', method='filter_annotations')
+    spans__isnull = BooleanFilter(field_name='spans', method='filter_annotations')
+    categories__isnull = BooleanFilter(field_name='categories', method='filter_annotations')
+    texts__isnull = BooleanFilter(field_name='texts', method='filter_annotations')
 
     def filter_annotations(self, queryset, field_name, value):
         queryset = queryset.annotate(num_annotations=Count(
@@ -27,7 +26,8 @@ class DocumentFilter(FilterSet):
 
     class Meta:
         model = Document
-        fields = ('project', 'text', 'created_at', 'updated_at',
-                  'doc_annotations__label__id', 'seq_annotations__label__id',
-                  'doc_annotations__isnull', 'seq_annotations__isnull', 'seq2seq_annotations__isnull',
-                  'speech2text_annotations__isnull')
+        fields = (
+            'project', 'text', 'created_at', 'updated_at',
+            'categories__label__id', 'spans__label__id',
+            'categories__isnull', 'spans__isnull', 'texts__isnull'
+        )
diff --git a/backend/api/managers.py b/backend/api/managers.py
index 1d1fb2b0..90001b0a 100644
--- a/backend/api/managers.py
+++ b/backend/api/managers.py
@@ -10,7 +10,7 @@ class AnnotationManager(Manager):
         label_count = Counter()
         user_count = Counter()
         docs = project.examples.all()
-        annotations = self.filter(document_id__in=docs.all())
+        annotations = self.filter(example_id__in=docs.all())
 
         for d in annotations.values('label__text', 'user__username').annotate(Count('label'), Count('user')):
             label_count[d['label__text']] += d['label__count']
@@ -25,7 +25,7 @@ class Seq2seqAnnotationManager(Manager):
         label_count = Counter()
         user_count = Counter()
         docs = project.examples.all()
-        annotations = self.filter(document_id__in=docs.all())
+        annotations = self.filter(example_id__in=docs.all())
 
         for d in annotations.values('text', 'user__username').annotate(Count('text'), Count('user')):
             label_count[d['text']] += d['text__count']
diff --git a/backend/api/models.py b/backend/api/models.py
index 710d98c8..ff448079 100644
--- a/backend/api/models.py
+++ b/backend/api/models.py
@@ -45,31 +45,31 @@ class Project(PolymorphicModel):
 class TextClassificationProject(Project):
 
     def get_annotation_class(self):
-        return DocumentAnnotation
+        return Category
 
 
 class SequenceLabelingProject(Project):
 
     def get_annotation_class(self):
-        return SequenceAnnotation
+        return Span
 
 
 class Seq2seqProject(Project):
 
     def get_annotation_class(self):
-        return Seq2seqAnnotation
+        return TextLabel
 
 
 class Speech2textProject(Project):
 
     def get_annotation_class(self):
-        return Speech2textAnnotation
+        return TextLabel
 
 
 class ImageClassificationProject(Project):
 
     def get_annotation_class(self):
-        return ImageCategoryLabel
+        return Category
 
 
 class Label(models.Model):
@@ -116,10 +116,19 @@ class Label(models.Model):
 class Example(PolymorphicModel):
     meta = models.JSONField(default=dict)
     filename = models.FileField(default='.')
-    project = models.ForeignKey(Project, related_name='examples', on_delete=models.CASCADE)
+    project = models.ForeignKey(
+        to=Project,
+        on_delete=models.CASCADE,
+        related_name='examples'
+    )
+    annotations_approved_by = models.ForeignKey(
+        to=User,
+        on_delete=models.SET_NULL,
+        null=True,
+        blank=True
+    )
     created_at = models.DateTimeField(auto_now_add=True)
     updated_at = models.DateTimeField(auto_now=True)
-    annotations_approved_by = models.ForeignKey(User, on_delete=models.SET_NULL, null=True, blank=True)
 
     @property
     def comment_count(self):
@@ -128,22 +137,26 @@ class Example(PolymorphicModel):
 
 class Document(Example):
     text = models.TextField()
-    example = models.OneToOneField(Example,
-                                   on_delete=models.CASCADE,
-                                   primary_key=True,
-                                   db_column='id',
-                                   parent_link=True)
+    example = models.OneToOneField(
+        to=Example,
+        on_delete=models.CASCADE,
+        primary_key=True,
+        db_column='id',
+        parent_link=True
+    )
 
     def __str__(self):
         return self.text[:50]
 
 
 class Image(Example):
-    example = models.OneToOneField(Example,
-                                   on_delete=models.CASCADE,
-                                   primary_key=True,
-                                   db_column='id',
-                                   parent_link=True)
+    example = models.OneToOneField(
+        to=Example,
+        on_delete=models.CASCADE,
+        primary_key=True,
+        db_column='id',
+        parent_link=True
+    )
 
     def __str__(self):
         return self.filename
@@ -151,8 +164,16 @@ class Image(Example):
 
 class Comment(models.Model):
     text = models.TextField()
-    example = models.ForeignKey(Example, related_name='comments', on_delete=models.CASCADE)
-    user = models.ForeignKey(User, on_delete=models.CASCADE, null=True)
+    example = models.ForeignKey(
+        to=Example,
+        on_delete=models.CASCADE,
+        related_name='comments'
+    )
+    user = models.ForeignKey(
+        to=User,
+        on_delete=models.CASCADE,
+        null=True
+    )
     created_at = models.DateTimeField(auto_now_add=True)
     updated_at = models.DateTimeField(auto_now=True)
 
@@ -166,7 +187,11 @@ class Comment(models.Model):
 
 class Tag(models.Model):
     text = models.TextField()
-    project = models.ForeignKey(Project, related_name='tags', on_delete=models.CASCADE)
+    project = models.ForeignKey(
+        to=Project,
+        on_delete=models.CASCADE,
+        related_name='tags'
+    )
 
     def __str__(self):
         return self.text
@@ -185,17 +210,35 @@ class Annotation(models.Model):
         abstract = True
 
 
-class DocumentAnnotation(Annotation):
-    document = models.ForeignKey(Document, related_name='doc_annotations', on_delete=models.CASCADE)
-    label = models.ForeignKey(Label, on_delete=models.CASCADE)
+class Category(Annotation):
+    example = models.ForeignKey(
+        to=Example,
+        on_delete=models.CASCADE,
+        related_name='categories'
+    )
+    label = models.ForeignKey(
+        to=Label,
+        on_delete=models.CASCADE
+    )
 
     class Meta:
-        unique_together = ('document', 'user', 'label')
+        unique_together = (
+            'example',
+            'user',
+            'label'
+        )
 
 
-class SequenceAnnotation(Annotation):
-    document = models.ForeignKey(Document, related_name='seq_annotations', on_delete=models.CASCADE)
-    label = models.ForeignKey(Label, on_delete=models.CASCADE)
+class Span(Annotation):
+    example = models.ForeignKey(
+        to=Example,
+        on_delete=models.CASCADE,
+        related_name='spans'
+    )
+    label = models.ForeignKey(
+        to=Label,
+        on_delete=models.CASCADE
+    )
     start_offset = models.IntegerField()
     end_offset = models.IntegerField()
 
@@ -204,34 +247,30 @@ class SequenceAnnotation(Annotation):
             raise ValidationError('start_offset is after end_offset')
 
     class Meta:
-        unique_together = ('document', 'user', 'label', 'start_offset', 'end_offset')
+        unique_together = (
+            'example',
+            'user',
+            'label',
+            'start_offset',
+            'end_offset'
+        )
 
 
-class Seq2seqAnnotation(Annotation):
-    # Override AnnotationManager for custom functionality
+class TextLabel(Annotation):
     objects = Seq2seqAnnotationManager()
-
-    document = models.ForeignKey(Document, related_name='seq2seq_annotations', on_delete=models.CASCADE)
-    text = models.CharField(max_length=500)
-
-    class Meta:
-        unique_together = ('document', 'user', 'text')
-
-
-class Speech2textAnnotation(Annotation):
-    document = models.ForeignKey(Document, related_name='speech2text_annotations', on_delete=models.CASCADE)
+    example = models.ForeignKey(
+        to=Example,
+        on_delete=models.CASCADE,
+        related_name='texts'
+    )
     text = models.TextField()
 
     class Meta:
-        unique_together = ('document', 'user')
-
-
-class ImageCategoryLabel(Annotation):
-    image = models.ForeignKey(Image, related_name='categories', on_delete=models.CASCADE)
-    label = models.ForeignKey(Label, on_delete=models.CASCADE)
-
-    class Meta:
-        unique_together = ('image', 'user', 'label')
+        unique_together = (
+            'example',
+            'user',
+            'text'
+        )
 
 
 class Role(models.Model):
diff --git a/backend/api/serializers.py b/backend/api/serializers.py
index 0152e5b1..8fc7c93f 100644
--- a/backend/api/serializers.py
+++ b/backend/api/serializers.py
@@ -7,13 +7,11 @@ from rest_framework.exceptions import ValidationError
 from rest_polymorphic.serializers import PolymorphicSerializer
 
 from .models import (DOCUMENT_CLASSIFICATION, SEQ2SEQ, SEQUENCE_LABELING,
-                     SPEECH2TEXT, AutoLabelingConfig, Comment, Document,
-                     DocumentAnnotation, Example, Image, ImageCategoryLabel,
-                     ImageClassificationProject, Label, Project, Role,
-                     RoleMapping, Seq2seqAnnotation, Seq2seqProject,
-                     SequenceAnnotation, SequenceLabelingProject,
-                     Speech2textAnnotation, Speech2textProject, Tag,
-                     TextClassificationProject)
+                     SPEECH2TEXT, AutoLabelingConfig, Category, Comment,
+                     Document, Example, Image, ImageClassificationProject,
+                     Label, Project, Role, RoleMapping, Seq2seqProject,
+                     SequenceLabelingProject, Span, Speech2textProject, Tag,
+                     TextClassificationProject, TextLabel)
 
 
 class UserSerializer(serializers.ModelSerializer):
@@ -89,7 +87,7 @@ class BaseDataSerializer(serializers.ModelSerializer):
         project = instance.project
         model = project.get_annotation_class()
         serializer = get_annotation_serializer(task=project.project_type)
-        annotations = model.objects.filter(document=instance.id)
+        annotations = model.objects.filter(example=instance.id)
         if request and not project.collaborative_annotation:
             annotations = annotations.filter(user=request.user)
         serializer = serializer(annotations, many=True)
@@ -225,51 +223,58 @@ class ProjectFilteredPrimaryKeyRelatedField(serializers.PrimaryKeyRelatedField):
         return queryset.filter(project=view.kwargs['project_id'])
 
 
-class DocumentAnnotationSerializer(serializers.ModelSerializer):
+class CategorySerializer(serializers.ModelSerializer):
     label = serializers.PrimaryKeyRelatedField(queryset=Label.objects.all())
-    document = serializers.PrimaryKeyRelatedField(queryset=Document.objects.all())
+    example = serializers.PrimaryKeyRelatedField(queryset=Example.objects.all())
 
     class Meta:
-        model = DocumentAnnotation
-        fields = ('id', 'prob', 'label', 'user', 'document', 'created_at', 'updated_at')
-        read_only_fields = ('user', )
-
-
-class SequenceAnnotationSerializer(serializers.ModelSerializer):
-    label = serializers.PrimaryKeyRelatedField(queryset=Label.objects.all())
-    document = serializers.PrimaryKeyRelatedField(queryset=Document.objects.all())
-
-    class Meta:
-        model = SequenceAnnotation
-        fields = ('id', 'prob', 'label', 'start_offset', 'end_offset', 'user', 'document', 'created_at', 'updated_at')
-        read_only_fields = ('user',)
-
-
-class Seq2seqAnnotationSerializer(serializers.ModelSerializer):
-    document = serializers.PrimaryKeyRelatedField(queryset=Document.objects.all())
-
-    class Meta:
-        model = Seq2seqAnnotation
-        fields = ('id', 'text', 'user', 'document', 'prob', 'created_at', 'updated_at')
+        model = Category
+        fields = (
+            'id',
+            'prob',
+            'user',
+            'example',
+            'created_at',
+            'updated_at',
+            'label',
+        )
         read_only_fields = ('user',)
 
 
-class Speech2textAnnotationSerializer(serializers.ModelSerializer):
-    document = serializers.PrimaryKeyRelatedField(queryset=Document.objects.all())
+class SpanSerializer(serializers.ModelSerializer):
+    label = serializers.PrimaryKeyRelatedField(queryset=Label.objects.all())
+    example = serializers.PrimaryKeyRelatedField(queryset=Example.objects.all())
 
     class Meta:
-        model = Speech2textAnnotation
-        fields = ('id', 'prob', 'text', 'user', 'document', 'created_at', 'updated_at')
+        model = Span
+        fields = (
+            'id',
+            'prob',
+            'user',
+            'example',
+            'created_at',
+            'updated_at',
+            'label',
+            'start_offset',
+            'end_offset',
+        )
         read_only_fields = ('user',)
 
 
-class ImageClassificationLabelSerializer(serializers.ModelSerializer):
-    label = serializers.PrimaryKeyRelatedField(queryset=Label.objects.all())
-    image = serializers.PrimaryKeyRelatedField(queryset=Image.objects.all())
+class TextLabelSerializer(serializers.ModelSerializer):
+    example = serializers.PrimaryKeyRelatedField(queryset=Example.objects.all())
 
     class Meta:
-        model = ImageCategoryLabel
-        fields = ('id', 'prob', 'label', 'user', 'image', 'created_at', 'updated_at')
+        model = TextLabel
+        fields = (
+            'id',
+            'prob',
+            'user',
+            'example',
+            'created_at',
+            'updated_at',
+            'text',
+        )
         read_only_fields = ('user',)
 
 
@@ -334,10 +339,10 @@ class AutoLabelingConfigSerializer(serializers.ModelSerializer):
 
 def get_annotation_serializer(task: str):
     mapping = {
-        DOCUMENT_CLASSIFICATION: DocumentAnnotationSerializer,
-        SEQUENCE_LABELING: SequenceAnnotationSerializer,
-        SEQ2SEQ: Seq2seqAnnotationSerializer,
-        SPEECH2TEXT: Speech2textAnnotationSerializer
+        DOCUMENT_CLASSIFICATION: CategorySerializer,
+        SEQUENCE_LABELING: SpanSerializer,
+        SEQ2SEQ: TextLabelSerializer,
+        SPEECH2TEXT: TextLabelSerializer
     }
     try:
         return mapping[task]
diff --git a/backend/api/tests/api/test_annotation.py b/backend/api/tests/api/test_annotation.py
index 53c70fbe..27d2f485 100644
--- a/backend/api/tests/api/test_annotation.py
+++ b/backend/api/tests/api/test_annotation.py
@@ -1,7 +1,7 @@
 from rest_framework import status
 from rest_framework.reverse import reverse
 
-from ...models import DOCUMENT_CLASSIFICATION, DocumentAnnotation
+from ...models import DOCUMENT_CLASSIFICATION, Category
 from .utils import (CRUDMixin, make_annotation, make_doc, make_label,
                     make_user, prepare_project)
 
@@ -30,7 +30,7 @@ class TestAnnotationList(CRUDMixin):
 
     def test_allows_project_member_to_bulk_delete_annotation(self):
         self.assert_delete(self.project.users[0], status.HTTP_204_NO_CONTENT)
-        count = DocumentAnnotation.objects.count()
+        count = Category.objects.count()
         self.assertEqual(count, 2)  # delete only own annotation
 
 
@@ -51,7 +51,7 @@ class TestSharedAnnotationList(CRUDMixin):
 
     def test_allows_project_member_to_bulk_delete_annotation(self):
         self.assert_delete(self.project.users[0], status.HTTP_204_NO_CONTENT)
-        count = DocumentAnnotation.objects.count()
+        count = Category.objects.count()
         self.assertEqual(count, 0)  # delete all annotation in the doc
 
 
diff --git a/backend/api/tests/api/test_statistics.py b/backend/api/tests/api/test_statistics.py
index 8ec7b478..be5eb555 100644
--- a/backend/api/tests/api/test_statistics.py
+++ b/backend/api/tests/api/test_statistics.py
@@ -34,8 +34,8 @@ class TestStatisticsAPI(APITestCase, TestUtilsMixin):
         )
         doc1 = mommy.make('Document', project=cls.project)
         doc2 = mommy.make('Document', project=cls.project)
-        mommy.make('DocumentAnnotation', document=doc1, user=super_user)
-        mommy.make('DocumentAnnotation', document=doc2, user=other_user)
+        mommy.make('Category', example=doc1, user=super_user)
+        mommy.make('Category', example=doc2, user=other_user)
         cls.url = reverse(viewname='statistics', args=[cls.project.id])
         cls.doc = Document.objects.filter(project=cls.project)
 
diff --git a/backend/api/tests/api/utils.py b/backend/api/tests/api/utils.py
index 518274fb..72305d47 100644
--- a/backend/api/tests/api/utils.py
+++ b/backend/api/tests/api/utils.py
@@ -102,12 +102,12 @@ def make_comment(doc, user):
 
 def make_annotation(task, doc, user):
     annotation_model = {
-        DOCUMENT_CLASSIFICATION: 'DocumentAnnotation',
-        SEQUENCE_LABELING: 'SequenceAnnotation',
-        SEQ2SEQ: 'Seq2seqAnnotation',
-        SPEECH2TEXT: 'Speech2textAnnotation'
+        DOCUMENT_CLASSIFICATION: 'Category',
+        SEQUENCE_LABELING: 'Span',
+        SEQ2SEQ: 'TextLabel',
+        SPEECH2TEXT: 'TextLabel'
     }.get(task)
-    return mommy.make(annotation_model, document=doc, user=user)
+    return mommy.make(annotation_model, example=doc, user=user)
 
 
 def prepare_project(task: str = 'Any', collaborative_annotation=False):
diff --git a/backend/api/tests/test_models.py b/backend/api/tests/test_models.py
index 51e2f705..fee0c46d 100644
--- a/backend/api/tests/test_models.py
+++ b/backend/api/tests/test_models.py
@@ -3,8 +3,7 @@ from django.db.utils import IntegrityError
 from django.test import TestCase, override_settings
 from model_mommy import mommy
 
-from ..models import (DocumentAnnotation, Label, Seq2seqAnnotation,
-                      SequenceAnnotation, Speech2textAnnotation)
+from ..models import Category, Label, Span, TextLabel
 
 
 @override_settings(STATICFILES_STORAGE='django.contrib.staticfiles.storage.StaticFilesStorage')
@@ -16,7 +15,7 @@ class TestTextClassificationProject(TestCase):
 
     def test_get_annotation_class(self):
         klass = self.project.get_annotation_class()
-        self.assertEqual(klass, DocumentAnnotation)
+        self.assertEqual(klass, Category)
 
 
 @override_settings(STATICFILES_STORAGE='django.contrib.staticfiles.storage.StaticFilesStorage')
@@ -28,7 +27,7 @@ class TestSequenceLabelingProject(TestCase):
 
     def test_get_annotation_class(self):
         klass = self.project.get_annotation_class()
-        self.assertEqual(klass, SequenceAnnotation)
+        self.assertEqual(klass, Span)
 
 
 @override_settings(STATICFILES_STORAGE='django.contrib.staticfiles.storage.StaticFilesStorage')
@@ -40,7 +39,7 @@ class TestSeq2seqProject(TestCase):
 
     def test_get_annotation_class(self):
         klass = self.project.get_annotation_class()
-        self.assertEqual(klass, Seq2seqAnnotation)
+        self.assertEqual(klass, TextLabel)
 
 
 @override_settings(STATICFILES_STORAGE='django.contrib.staticfiles.storage.StaticFilesStorage')
@@ -52,7 +51,7 @@ class TestSpeech2textProject(TestCase):
 
     def test_get_annotation_class(self):
         klass = self.project.get_annotation_class()
-        self.assertEqual(klass, Speech2textAnnotation)
+        self.assertEqual(klass, TextLabel)
 
 
 class TestLabel(TestCase):
@@ -109,36 +108,36 @@ class TestLabel(TestCase):
             self.fail(msg=ValidationError)
 
 
-class TestDocumentAnnotation(TestCase):
+class TestCategory(TestCase):
 
     def test_uniqueness(self):
-        a = mommy.make('DocumentAnnotation')
+        a = mommy.make('Category')
         with self.assertRaises(IntegrityError):
-            DocumentAnnotation(document=a.document, user=a.user, label=a.label).save()
+            Category(example=a.example, user=a.user, label=a.label).save()
 
 
 class TestSequenceAnnotation(TestCase):
 
     def test_uniqueness(self):
-        a = mommy.make('SequenceAnnotation')
+        a = mommy.make('Span')
         with self.assertRaises(IntegrityError):
-            SequenceAnnotation(document=a.document,
-                               user=a.user,
-                               label=a.label,
-                               start_offset=a.start_offset,
-                               end_offset=a.end_offset).save()
+            Span(example=a.example,
+                 user=a.user,
+                 label=a.label,
+                 start_offset=a.start_offset,
+                 end_offset=a.end_offset).save()
 
     def test_position_constraint(self):
         with self.assertRaises(ValidationError):
-            mommy.make('SequenceAnnotation',
+            mommy.make('Span',
                        start_offset=1, end_offset=0).clean()
 
 
 class TestSeq2seqAnnotation(TestCase):
 
     def test_uniqueness(self):
-        a = mommy.make('Seq2seqAnnotation')
+        a = mommy.make('TextLabel')
         with self.assertRaises(IntegrityError):
-            Seq2seqAnnotation(document=a.document,
-                              user=a.user,
-                              text=a.text).save()
+            TextLabel(example=a.example,
+                      user=a.user,
+                      text=a.text).save()
diff --git a/backend/api/views/annotation.py b/backend/api/views/annotation.py
index a119d51c..9b9475e9 100644
--- a/backend/api/views/annotation.py
+++ b/backend/api/views/annotation.py
@@ -25,7 +25,7 @@ class AnnotationList(generics.ListCreateAPIView):
 
     def get_queryset(self):
         model = self.project.get_annotation_class()
-        queryset = model.objects.filter(document=self.kwargs['doc_id'])
+        queryset = model.objects.filter(example=self.kwargs['doc_id'])
         if not self.project.collaborative_annotation:
             queryset = queryset.filter(user=self.request.user)
         return queryset
@@ -33,11 +33,11 @@ class AnnotationList(generics.ListCreateAPIView):
     def create(self, request, *args, **kwargs):
         if self.project.single_class_classification:
             self.get_queryset().delete()
-        request.data['document'] = self.kwargs['doc_id']
+        request.data['example'] = self.kwargs['doc_id']
         return super().create(request, args, kwargs)
 
     def perform_create(self, serializer):
-        serializer.save(document_id=self.kwargs['doc_id'], user=self.request.user)
+        serializer.save(example_id=self.kwargs['doc_id'], user=self.request.user)
 
     def delete(self, request, *args, **kwargs):
         queryset = self.get_queryset()
@@ -49,22 +49,23 @@ class AnnotationDetail(generics.RetrieveUpdateDestroyAPIView):
     lookup_url_kwarg = 'annotation_id'
     swagger_schema = None
 
+    @property
+    def project(self):
+        return get_object_or_404(Project, pk=self.kwargs['project_id'])
+
     def get_permissions(self):
-        project = get_object_or_404(Project, pk=self.kwargs['project_id'])
-        if project.collaborative_annotation:
+        if self.project.collaborative_annotation:
             self.permission_classes = [IsAuthenticated & IsInProjectOrAdmin]
         else:
             self.permission_classes = [IsAuthenticated & IsInProjectOrAdmin & IsOwnAnnotation]
         return super().get_permissions()
 
     def get_serializer_class(self):
-        project = get_object_or_404(Project, pk=self.kwargs['project_id'])
-        self.serializer_class = get_annotation_serializer(task=project.project_type)
+        self.serializer_class = get_annotation_serializer(task=self.project.project_type)
         return self.serializer_class
 
     def get_queryset(self):
-        project = get_object_or_404(Project, pk=self.kwargs['project_id'])
-        model = project.get_annotation_class()
+        model = self.project.get_annotation_class()
         self.queryset = model.objects.all()
         return self.queryset
 
diff --git a/backend/api/views/example.py b/backend/api/views/example.py
index 5a73805b..8d200e3e 100644
--- a/backend/api/views/example.py
+++ b/backend/api/views/example.py
@@ -10,7 +10,8 @@ from rest_framework.response import Response
 from ..filters import DocumentFilter
 from ..models import Document, Example, Image, Project
 from ..permissions import IsInProjectReadOnlyOrAdmin
-from ..serializers import DocumentSerializer, ExampleSerializer, ImageSerializer
+from ..serializers import (DocumentSerializer, ExampleSerializer,
+                           ImageSerializer)
 
 
 class ExampleList(generics.ListCreateAPIView):
diff --git a/backend/api/views/statistics.py b/backend/api/views/statistics.py
index 17dc71d3..bdbed40b 100644
--- a/backend/api/views/statistics.py
+++ b/backend/api/views/statistics.py
@@ -39,20 +39,20 @@ class StatisticsAPI(APIView):
     def _get_user_completion_data(annotation_class, annotation_filter):
         all_annotation_objects = annotation_class.objects.filter(annotation_filter)
         set_user_data = collections.defaultdict(set)
-        for ind_obj in all_annotation_objects.values('user__username', 'document__id'):
-            set_user_data[ind_obj['user__username']].add(ind_obj['document__id'])
+        for ind_obj in all_annotation_objects.values('user__username', 'example__id'):
+            set_user_data[ind_obj['user__username']].add(ind_obj['example__id'])
         return {i: len(set_user_data[i]) for i in set_user_data}
 
     def progress(self, project):
         docs = project.examples
         annotation_class = project.get_annotation_class()
         total = docs.count()
-        annotation_filter = Q(document_id__in=docs.all())
+        annotation_filter = Q(example_id__in=docs.all())
         user_data = self._get_user_completion_data(annotation_class, annotation_filter)
         if not project.collaborative_annotation:
             annotation_filter &= Q(user_id=self.request.user)
         done = annotation_class.objects.filter(annotation_filter)\
-            .aggregate(Count('document', distinct=True))['document__count']
+            .aggregate(Count('example', distinct=True))['example__count']
         remaining = total - done
         return {'total': total, 'remaining': remaining, 'user': user_data}