Database schema conventions

Schema for CHT database objects

CouchDB (and PouchDB in the browser) is a JSON-based NoSQL datastore that we use to store our data. While unlike SQL databases there is no enforced schema, code still follows conventions, and this document aims to describe the schema as defined by how our code operates.

In this document “record” means a JSON object that resides in CouchDB or PouchDB.

General record data structure

Contacts (Persons and Places)

Contacts are either places (e.g. clinic), groupings (e.g. family) or people (e.g. a patient or CHW).

The type property of contact records depends on the version of Medic you are running:

• If you are running 3.7 or later you get to configure your contact hierarchy, and the type of contacts is contact, and the configured type is in the contact_type property.
• In earlier versions the type depended on hierarchical location of the contact. There are 3 hard coded place types: district_hospital, health_centre and clinic and one people type person. These place names are often meaningless (hence the configurable contact hierarchy in later versions) to the configured project, and are textually (ie in the UI not in data structures) renamed to mean other things. For example, as clinic is the lowest level it is often used to represent a family.

Places

Represent either an actual physical location such as a clinic, or a grouping such as a family or region.

Unless a place is at the top of the hierarchy it has a parent place.

Each location has a primary contact, which is a person contact stored in the contact property.

People

People are both patients in the system and users of the system, such as CHWs or Nurses. Users have additional records marking them as users of the system (see User below).

People always have a parent place.

Parent hierarchy representation

Contacts store their parent hierarchy as a minified hierarchical structure, which records the _id of each parent up until the top of the hierarchy:

{
  type: 'person',
  name: 'A patient',
  parent: {
    _id: 'clinic-id',
    parent: {
      _id: 'health_centre-id',
      parent: {
        _id: 'district_hospital-id'
      }
    }
  }
}

Generally when contacts are used in the app they are first “hydrated”, with the rest of the information filled in from their parent’s place documents:

{
  type: 'person',
  name: 'A patient',
  parent: {
    _id: 'clinic-id',
    name: 'A clinic',
    reported_date: 1234,
    ... // etc
    parent: {
      _id: 'health_centre-id',
      name: 'A Health Centre',
      reported_date: 1134,
      ... // etc
      parent: {
        _id: 'district_hospital-id',
        name: 'THE District Hospital',
        reported_date: 1034,
        ... // etc
      }
    }
  }
}

See Also: Document hydration

As of version 3.10, you can connect contacts with other documents via the linked_docs property. This allows the app to have access to these linked documents when the contact is used.

Like the parent hierarchy, linked docs are stored as a minified object, where every linked doc is identified by a string tag and the UUID of the document it represents.

{
  type: 'person',
  name: 'A patient',
  parent: {
    _id: 'clinic-id',
  },
  linked_docs: {
    custom_tag1: 'some-contact-id',
    custom_tag2: 'other-contact-id',
    custom_tag3: 'report-id',
    ... // etc
  },
}

Linked docs are shallowly “hydrated” along with the parent hierarchy:

{
  type: 'person',
  name: 'A patient',
  parent: {
    _id: 'clinic-id',
    name: 'A clinic',
    reported_date: 1234,
    ... // etc
    parent: {
      _id: 'health_centre-id',
      name: 'A Health Centre',
      reported_date: 1134,
      ... // etc
      parent: {
        _id: 'district_hospital-id',
        name: 'THE District Hospital',
        reported_date: 1034,
        ... // etc
      }
    }
  },
  linked_docs: {
    custom_tag1: {
      _id: 'some-contact-id',
      name: 'some contact',
      type: 'person',
      parent: { _id: 'other-clinic' },
      reported_date: 4569,
      ... // etc
    },
    custom_tag2: {
      _id: 'other-contact-id',
      name: 'other contact',
      type: 'clinic',
      parent: { _id: 'health_center' },
      ... // etc
    },
    custom_tag3: {
      _id: 'report-id',
      form: 'FORM',
      contact: { _id: 'submitter-id' },
      ... // etc
    },
  },
}

Reports

Reports are created by users filling out and submitting forms, as well as sending in SMS.

All reports:

• Use the data_record type
• Have their fields stored in the fields property
• Have the report author’s phone number (if it exists) stored in the from field
• Store the form’s identifier in the form field
• May have a contact property, which is a minified version of the report author’s contact and its hierarchy (see above)

Reports can and should be linked to a contact when possible. The report’s associated contact (sometimes called the report’s subject) can be either a person or place. The link between report and contact is established by defining one of the following properties within the report:

1. A person shortcode or uuid at doc.fields.patient_id, doc.fields.patient_uuid, or doc.patient_id
2. A place shortcode or uuid at doc.fields.place_id or doc.place_id.

Additionally, SMS reports:

• Have an sms_message property which contains, among other things, the raw SMS
• May not have a contact property if the SMS comes from a phone number that does not have an associated contact

Additionally, XML reports:

• Have the XML file that Enketo (the XForm renderer used) generates as an attachment
• Have a content_type property of xml

Forms

SMS forms are defined in application config.

XML forms are stored in the database and have:

• An _id of form:<formname>
• The type of form
• The actual XML Xforms definition attached

XML forms are defined as XForm XML files

Users

Users represent credentials and roles / permissions for accessing the application. This can either be:

• people who can log into the application, such as CHWs or Nurses
• or credentials granting external software restricted permissions to perform certain tasks, such as allowing an external service permission to write reports via the api.

User records have at least:

• An _id of org.couchdb.user:<username>
• A name which is the same as <username> above
• A roles array

There are two slightly different copies of this record stored.

The record in the _users database includes:

• The type of user
• The password hash and associated data

The _users database is what CouchDB uses for authentication and is only editable by administrative users, so is authoritative when it comes to roles and the like.

The medic database stores a copy of roles and permissions along with:

• The type of user-settings
• They may have a contact_id field that is the _id of the person that the user is attached to
• They may also have a facility_id field that is the _id of the place that the user is attached to
• They may also have a known field. If this field is true, it means the user has logged in once. Otherwise, it will be undefined.

Note that SMS users do not have a users record: their phone number will be attached to a person record, but they do not have a user because they do not access the application.

Users then, can be represented by up to 3 docs:

• a person document that represents a physical human being in our hierarchy of places and people
• a users document that represents authorisation and authentication information for physical people or authenticated external services
• a user-settings document that ties the user and person documents together

Tasks

Partner configuration code running inside the Core Framework can cause tasks to appear within the Tasks tab. Each task in the tab is powered by a task document. Task documents are:

• updated only after the data for their emitting contact changes or every 7 days
• created in the database for any task due within the last 60 days
• immutable once their state is “terminal” (Cancelled, Completed, Failed)

To understand the difference between a task requester and a task owner, kindly see the example below:

• A CHW submits a delivery form. The patient is woman1, and she delivered one child child1.
• The delivery form generates a task, delivery_child_followup, but the task’s patient is child1 not woman1
• In the case of this task, the requester is woman1, because it was their delivery report that triggered task generation, but the owner is child1.

{
  "_id": "task~org.couchdb.user:agatha~pregReport~pregnancy-facility-visit-reminder~2~523435132468",
  "type": "task",
  "authoredOn": 523435132468,
  "user": "org.couchdb.user:agatha",
  "requester": "requester-contact-guid",
  "owner": "owner-contact-guid",
  "state": "Ready",
  "emission": {
    "_id": "pregReport~pregnancy-facility-visit-reminder~2",
    "forId": "for-contact-guid",
    "dueDate": "2000-01-01",
    "startDate": "1999-12-29",
    "endDate": "2000-01-08",
    "priority": "high",
    "priorityLabel": "task.priority",
    ...
  },
  "stateHistory": [{
    "state": "Ready",
    "timestamp": 523435132468,
  }],
}

Targets

Partner configuration code can configure targets to appear within the Targets/Analytics tab. Target documents are:

• one per analytics reporting period
• updated when the user loads the application or when they view the targets tab
• updated a maximum of once per day

{
  "_id": "target~2000-01~user-contact-guid~org.couchdb.user:agatha",
  "type": "target",
  "user": "org.couchdb.user:agatha",
  "owner": "user-contact-guid",
  "updated_date": 523435132468,
  "targets": [
    {
      "id": "deaths-this-month",
      ...
      "value": {
        "pass": 0,
        "total": 15
      }
    },
    ...
  ]
}

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