add reference model

backend/source/migrations/0002_reference.py

@@ -0,0 +1,31 @@
+# Generated by Django 4.2.7 on 2024-02-09 13:18
+
+import django.contrib.postgres.fields
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('contenttypes', '0002_remove_content_type_name'),
+        ('source', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Reference',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('object_id', models.PositiveIntegerField()),
+                ('location', models.CharField(blank=True, help_text='specific location of the reference in the source text', max_length=200)),
+                ('terminology', django.contrib.postgres.fields.ArrayField(base_field=models.CharField(max_length=200), blank=True, default=[], help_text='terminology used in the source text to describe this entity', size=5)),
+                ('mention', models.CharField(blank=True, choices=[('direct', 'directly mentioned'), ('implied', 'implied')], help_text='how is this entity presented in the text?', max_length=32)),
+                ('content_type', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to='contenttypes.contenttype')),
+                ('source', models.ForeignKey(help_text='the source text in which this references occurs', on_delete=django.db.models.deletion.CASCADE, to='source.source')),
+            ],
+            options={
+                'indexes': [models.Index(fields=['content_type', 'object_id'], name='source_refe_content_816b0e_idx')],
+            },
+        ),
+    ]

backend/source/models.py

@@ -1,7 +1,14 @@
 from django.db import models
+from django.contrib.postgres.fields import ArrayField
+from django.contrib.contenttypes.fields import GenericForeignKey
+from django.contrib.contenttypes.models import ContentType
 
 
 class Source(models.Model):
+    """
+    A Source is a text of any kind.
+    """
+
     name = models.CharField(
         max_length=200,
         blank=False,
@@ -15,3 +22,54 @@ class Source(models.Model):
 
     def __str__(self):
         return self.name
+
+class Reference(models.Model):
+    """
+    References link information to sources.
+
+    A Reference describes where and how a source refers to the information presented
+    in the database object.
+    """
+
+    # reference to the object
+    # c.f. https://docs.djangoproject.com/en/4.2/ref/contrib/contenttypes/#generic-relations
+
+    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
+    object_id = models.PositiveIntegerField()
+    content_object = GenericForeignKey("content_type", "object_id")
+
+    # reference to a source
+
+    source = models.ForeignKey(
+        to=Source,
+        on_delete=models.CASCADE,
+        help_text="the source text in which this references occurs",
+    )
+
+    # description of the reference
+
+    location = models.CharField(
+        max_length=200,
+        blank=True,
+        help_text="specific location of the reference in the source text",
+    )
+
+    terminology = ArrayField(
+        models.CharField(
+            max_length=200,
+        ),
+        default=[],
+        blank=True,
+        size=5,
+        help_text="terminology used in the source text to describe this entity",
+    )
+
+    mention = models.CharField(
+        max_length=32,
+        blank=True,
+        choices=[("direct", "directly mentioned"), ("implied", "implied")],
+        help_text="how is this entity presented in the text?",
+    )
+
+    class Meta:
+        indexes = [models.Index(fields=["content_type", "object_id"])]