1. Document database … one kind of NoSQL database
Store data that are documents, typically with some structure.
Similar documents are stored in collections.
Database consists of collections where each collection contains documents.
Popular language for describing data is JSON
e.g. {
'_id' : 1,
'name' : { 'first' : 'John', 'last' : 'Backus' },
'contribs' : [ 'Fortran', 'ALGOL', 'Backus-Naur Form', 'FP' ],
'awards' : [
'award' : 'W.W. McDowell Award',
'year' : 1967,
'by' : 'IEEE Computer Society'
}, {
'award' : 'Draper Prize',
'year' : 1993,
'by' : 'National Academy of Engineering' } ]

2. Each document has a unique object identifier{
'_id' : 1,
'name' : {
'first' : 'John',
'last' : 'Backus' },
'contribs' : [
'Fortran',
'ALGOL',
'Backus-Naur Form',
'FP' ],
'awards' : [
'award' : 'W.W. McDowell Award',
'year' : 1967,
'by' : 'IEEE Computer Society'
}, {
'award' : 'Draper Prize',
'year' : 1993,
'by' : 'National Academy of Engineering' } ]
Each document has a unique object identifier
Name is composite
Contribs is multi-valued – an array
Awards is multi-valued
Each award is composite

3. employee: {
'_id' : ,
‘Fname' : 'John',
‘Lname ‘: ‘Smith’,
‘Minit ‘: ‘B’
‘Bdate’ : ‘ ’,
… etc
Dependents:[
‘dependent_name’: ‘Michael’,
‘sex’:’M’,
‘Bdate’: ’,
‘Relationship’: ‘Son
},{
‘dependent_name’: ‘Alice’,
‘sex’:’F’,
‘Bdate’: ’,
‘Relationship’: ‘Daughter’
‘dependent_name’: ‘Elizabeth’,
‘Relationship’: ‘Spouse’} ] }
Easy to model employees and dependents in one collection as there is a natural hierarchy (the one-to-many relationship)

4. How does one handle the supervises relationship…
employee: {
'_id' : ,
‘Fname' : ’James',
‘Lname ‘: ‘Borg’,
‘Minit ‘: ‘E’
‘Bdate’ : ‘ ’,
… etc
Dependents:[
… } ]
Supervises:[
'_id' : ,
‘Fname' : ‘Franklin',
‘Lname ‘: ‘Wong’,
‘Minit ‘: ‘T’
‘Bdate’ : ‘ ’, }
How does one handle the supervises relationship…
Could embed each employee within their supervisor
Notice that each employee will have a Supervises entry

5. How does one handle the supervises relationship…
Or, each employee is a separate document with references to other employees via the object identifier
Don’t expect to be able to specify a join operation … rather need to program this
Employee: {
'_id' : ,
‘Fname' : James',
‘Lname ‘: ‘Borg’,
‘Minit ‘: ‘E’
‘Bdate’ : ‘ ’,
… etc
Dependents:[
… } ]
Supervises [ ObjectID(‘ ’), ObjectID(‘ ’), …
employee:[
'_id' : ,
‘Fname' : ‘Franklin',
‘Lname ‘: ‘Wong’,
‘Minit ‘: ‘T’
‘Bdate’ : ‘ ’,
Supervises: [ObjectID:(‘ ’)] }
To get the employees supervised by
e = db.employees.find ( { _id: } )
Subordinates = db.employees.find (
{ _id: $in e.Supervises} )