1. Database Models
Files and models
Copyright © Curt Hill

2. Then and Now
In the olden days (prior to 1980) there were three major database models
Relational
Hierarchical
Network
Each of these had commercial examples
In the new millennium there are several new ones as well
Copyright © Curt Hill

3. Models Olden days More recently add: Relational Hierarchical Network
Key Value
Columnar
Document
Graph
More to come?
Copyright © Curt Hill

4. File Structures
In the olden days database were classified by their file structures
Now we mostly hide the file structure
The relational model only needs sequential files, but always uses stronger file structures
Copyright © Curt Hill

5. Indexed Files Require links between records The link is a disk address
Either Cylinder, Track, Sector
Or Block number
The links connect the indices with their corresponding data
This complicates their support
Copyright © Curt Hill

6. Index Sequential File Tree
Charles Kline Roberts Zane
Charles Kline Roberts Zane
Abel Bag Casey Charles
Able Bart Calvin Charles Dean Easy Frank Kline Larry Morris Roberts Smith Taylor Vernon Zane
Easy Frank Jam Kline
Leestra May Roberts
Singer Smith Taylor Vernon Zane
Each block should represent one disk block, such as a sector
The top level contains the keys only
The bottom level contains key and data
We can sequentially process the bottom level to get all names
We can randomly enter the tree and find any name with just two accesses
Copyright © Curt Hill

7. Relationship types
Expresses the cardinality or arity of the relationship
One to one
One to many
Many to many
Copyright © Curt Hill

8. Relational Form is that of a table Each table has Row is a record
A fixed number of columns
A variable number of rows
Row is a record
Column contains all the fields of one type
Copyright © Curt Hill

9. Relational Currently the dominant model
Substantial theoretical foundation
Many very popular implementations
Oracle, SQLServer, Postgres, MySQL
Has the most popular query language
Structured Query Language (SQL)
Copyright © Curt Hill

10. Relational Picture
Copyright © Curt Hill

11. Relational Model Files
Simplest theoretical file structure
Collection of sequential files
There are no links needed in a sequential file
Implied one to one between adjacent rows
This gives the DBMS the choice of how to implement
Performance issues if the DBMS only uses sequential files
Copyright © Curt Hill

12. Relational Model
They are fair to any view, not favoring one over the other
Have the best theoretical underpinning
Relational algebra and calculus
Great amounts of research
The only redundancy should be linking keys
Copyright © Curt Hill

13. Hierarchical Form is that of a tree
Only the one to many link is allowed
Typically favors one particular view of the data
Least popular model
Some redundancy is present because only one pointer may refer to a node
IMS by IBM for mainframes, SAS Institute’s System 2000
Copyright © Curt Hill

14. Hierarchical Model A.J. Baker 101 College St Asst. Prof Barb Jones
2401 Central Ave
Assoc. Prof
Hist 202
Hist 341
CS 122
CS 161
CIS 385
1028
1158
1032
1021
1026
1058
1144
1298
1036
1026
1416
1591
1428
1126
1028
Copyright © Curt Hill
1416

15. Network Model Examples: VAX DBMS (later acquired by Oracle)
Similar to hierarchical
Linked objects
Now allow many to many links
Now possible to start in different places and still find what is needed
Favors more views but not all
The many links does complicate maintenance
Virtually all redundancy may be eliminated with this model
The links keep us from needing two copies of a key
Examples: VAX DBMS (later acquired by Oracle)
Copyright © Curt Hill

16. More on Network Model
The database is often organized in owner-member chains
An owner is the head of chain
The members are chained together
The network is woven together with many such chains
Instead of a object pointing at many items it points at the head of a chain of items
Copyright © Curt Hill

17. Network Model A.J. Baker 101 College St Asst. Prof Barb Jones
2401 Central Ave
Assoc. Prof
Hist 202
Hist 341
CS 122
CS 161
CIS 385
1028
1158
This still needs some work to redo the owner-member chains
1032
1021
1026
1058
1144
1298
1036
1026
1416
1591
1428
1126
1028
Copyright © Curt Hill
1416

18. Weren’t There Just Three?
The three models store mostly ASCII text:
Numbers
Strings
Things that could be displayed using a typewriter
There are many other types of data
Graphics
Audio recordings
Video
Copyright © Curt Hill

19. Object-Oriented Programming
Early days: data as something to be manipulated by external programs
In the 80s and 90s object oriented programming paradigm became standard
Now: data is part of an object
Object encapsulates both the raw data and the operations used to manipulate it
Data is not directly accessible
Copyright © Curt Hill

20. Object Example Automobile accelerator pedal is data
Cruise control is an object
Data:
Velocity
Position of accelerator
Brake
Operations:
Set
Coast
Disable
Copyright © Curt Hill

21. Object Oriented Database
Next step or not?
Want to store data that DB does not know how to manipulate
Not always ASCII text
The solution is a program with persistent (disk based) data
The problem is that this approach cuts itself off from the theory base
Copyright © Curt Hill

22. Object Relational Database
Introduce object support into relational database
Typical RDB may be accessed by a text based client program, as well as application programs
The usual support for unusual data is the BLOB
Binary Large OBject
We retain the virtues of relational model
But, there is very little that can be done with the BLOB, other than access
Copyright © Curt Hill

23. NoSQL No SQL or Not Only SQL Relaxation of relational DB principles
Usually a key-value store
Often used for the massive data sets that cause performance issues for relational and other models
This group needs the theoretical foundation that relational has
Will consider much later
Copyright © Curt Hill

24. Key Value Simplest model
There is a key (which must be unique) linked to a group of values
It gets more interesting if the values may include key value pairs as well
Two examples: Riak and Reddis
Copyright © Curt Hill

25. KV Picture
Copyright © Curt Hill

26. Columnar
A lot of similarity to relational, but the dominant item is the column not the row
We lack rectangularity that relational has
Columns are stored together
Halfway between Relational and Key Value
HBase, Cassandra, HyperTable are examples
Copyright © Curt Hill

27. Columnar
Copyright © Curt Hill

28. Document
The basic object is now a document instead of a simple field like a number
Each document has an ID and other identifying values
Examples: MongoDB and CouchDB
Copyright © Curt Hill

29. Graph
A mathematical graph consists of nodes (the data) and links between these
Used for highly interconnected data
Processing rides the links
NeoJ is an example
Copyright © Curt Hill