The document discusses different database models: - The relational model was proposed by E.F. Codd and organizes data into tables with rows and columns. Popular relational DBMS include Oracle, SQL Server, and Access. - The hierarchical model uses a tree structure where each item has a single predecessor and subordinates. It is natural for applications with parent-child relationships. - The network model is a generalization of the hierarchical model, allowing many-to-many relationships through multiple parent segments connected through graphs. - Other models discussed include the AI frame model which uses slots to flexibly arrange related information similarly to object-oriented representations.

1. RELATIONAL MODEL
OF DATABASES AND
OTHER CONCEPTS OF
DATABASES​
BY EDWIN JACOB, PRANAV AND KARTHIK SUNDARMANI

2. Database Model
• A Database model defines the logical design and structure of a database and
defines how data will be stored, accessed and updated in a database
management system. The various types of database models are
• Hierarchical Model
• Network Model
• Relational Model

3. Relational Model in DBMS
• Relational Model was proposed by E.F. Codd to model data in the form of relations or tables.
• The model is comprised of rows and columns that use SQL as a query language for
maintaining and querying the databases.
• The basic structure of data in relational model is tables.
• Tables are also known as relations in relational model.
• Some popular relational data base management systems software's are
• DB2 And Informix Dyanamic Server- IBM
• Oracle And RDB – Oracle
• SQL Server And Access - Microsoft

4. Benefits and Challenges of the Relational
Model
• Databases that use the relational model have advantages over those that use
other models. These include simplicity of organization, ease of creation, ease of
data retrieval, built-in data integrity, flexibility of queries (including the fact that
programmers can write queries that weren’t anticipated by the database
designer), and less data redundancy (due to data normalization).
• However, o system is perfect. The relational model falls short in scalability,
difficulty of setup, and slower searches and queries when compared to other
database models.

5. Why do we need a Relational Database Model?
• Database Management System is software that permits the user to create, define, manage and
control the functions of the database.
• For better understanding, the Relational database model is used as an extension of the database
lying under the relational values. The RDBMS is entirely based on the relational model broadly
deployed in many applications.
• It is a common choice for information storage in a database especially in maintaining financial
records, logistics data, manufacturing products, personnel data, and so on. It replaced the
legacy of hierarchical databases and network databases because of its simple implementation
and administration features.
• Initially, RDBMS faced many failures but after many advancements it became a popular hit
and applied in many reliable applications.

6. IMPORTANT TERMINOLOGIES
• Attribute: Each column in a table is called Attributes. Attributes are the
properties that define a relation.
• Tuple: Each row in the relation is known as tuple.
• Degree: The number of attributes in the relation is known as degree of the
relation.
• Cardinality: The number of tuples in a relation is known as cardinality.
• Tables: Tables are stored along with entities.

7. Example : Historical Bridge Work Relation
• consider the relation which might record historical experience with different types of bridges
accumulated by a particular agency. The actual instances or rows of data are hypothetical. The
attributes of this relation are:
• PROJECT NUMBER - a 6-digit code identifying the particular project.
• TYPE OF BRIDGE - a text field describing the bridge type. (For retrieval purposes, a numerical
code might also be used to describe bridge type to avoid any differences in terminology to
describe similar bridges).
• LOCATION - The location of the project.
• CROSSING - What the bridge crosses over, eg. a river.
• SITE CONDITIONS - A brief description of the site peculiarities.

8. • ERECTION TIME - Time required to erect a bridge, in months.
• SPAN - Span of the bridge in feet.
• DATE - Year of bridge completion.
• ACTUAL-ESTIMATED COSTS - Difference of actual from estimated costs.
• These attributes could be used to answer a variety of questions concerning
construction experience useful during preliminary planning.

9. Cont….
• As an example, suppose that a bridge is to be built with a span of 250 feet, located in Pittsburgh PA, and crossing a
river with limestone sub-strata. In initial or preliminary planning, a designer might query the database four
separate times as follows:
• SELECT from BRIDGEWORK where SPAN > 200 and SPAN < 300 and where CROSSING = "river"
• SELECT from BRIDGEWORK where SPAN > 200 and SPAN < 300 and where SITE CONDITIONS = "Limestone"
• SELECT from BRIDGEWORK where TYPE OF BRIDGE = "Steel Plate Girder" and LOCATION = "PA"
• SELECT from BRIDGEWORK where SPAN < 300 and SPAN > 200 and ESTIMATED LESS ACTUAL COST <
100,000.
• Each SELECT operation would yield the bridge examples in the database which corresponds to the desired
selection criteria. In practice, an input/output interpreter program should be available to translate these inquiries to
and from the DBM and an appropriate problem oriented language.

10. Cont….
• The four queries may represent subsequent thoughts of a designer faced with
these problem conditions. He or she may first ask, "What experience have we
had with bridges of this span over rivers?" "What experience have we had with
bridges of this span with these site conditions? What is our experience with steel
girder bridges in Pennsylvania? For bridges of this span, how many and which
were erected without a sizable cost overrun? We could pose many more
questions of this general type using only the small data table.

11. Other Conceptual Models of Databases
• While the relational model offers a considerable amount of flexibility and
preserves considerable efficiency, there are several alternative models for
organizing databases,
• Hierarchical model
• Network model
• AI based model

12. Hierarchical Database Model
• The hierarchical model is a tree structure in which information is organized as
branches and nodes from a particular base.
• As an example Given below, hierarchical structure for rented equipment costs. In
this case, each piece of equipment belongs to a particular supplier and has a cost
which might vary by the duration of use. To find the cost of a particular piece of
equipment from a particular supplier, a query would first find the supplier, then
the piece of equipment and then the relevant price.

13. Example 1
• The hierarchical model has the characteristic that each item
has a single predecessor and a variable number of
subordinate data items.
• This structure is natural for many applications, such as the
equipment cost information described above. However, it
might be necessary to construct similar hierarchies for each
project to record the equipment used or for each piece of
equipment to record possible suppliers.
• Otherwise, generating these lists of assignments from the
database illustrated in the Figure would be difficult.
• For example, finding the least expensive supplier of a
crane might involve searching every supplier and every
equipment node in the database to find all crane prices.

14. Example 2
• Let us assume that we have a main directory
which contains other subdirectories. Each
subdirectory contains more files and directories.
Each directory or file can be in one directory only
i.e. it has only one parent.
• Here A is the main directory i.e. the root
node. B1 and B2 are their child or subdirectories.
B1 and B2 also have two children C1, C2 and C2,
C3 respectively. They may be directories or other
files. This depicts one- to- many relationships.

15. Advantages
• Promotes data sharing.
• It is conceptually simple due to the parent-child relationship.
• Database security is enforced.
• Efficient with 1: N relationships.
• A clear chain of command or authority.
• Increases specialization.
• High performance.
• Clear results.

16. Cont….
• A user can retrieve data very quickly due to the presence of explicit links
between the table structures.
• The referential integrity is built in and automatically enforced due to which a
record in a child table must be linked to an existing record in a parent table,
along with that if a record deleted in the parent table then that will cause all
associated records in the child table to be deleted as well.

17. Disadvantages
• When a user needs to store a record in a child table that is currently unrelated to
any record in a parent table, it gets difficulty in recording and user must record
an additional entry in the parent table.
• This type of database cannot support complex relationships, and there is also a
problem of redundancy, which can result in producing inaccurate information
due to the inconsistent recording of data at various sites.

18. Cont….
• Change in structure leads to change in all application programs.
• M: N relationship is not supported.
• No data manipulation or data definition language.
• Lack of standards.
• Poor flexibility
• Communication barriers
• Organizational Disunity.
• Rigid structure

19. Network Model
• This model was formalized by the Database Task group in the 1960s. This model is the
generalization of the hierarchical model.
• This model can consist of multiple parent segments and these segments are grouped
as levels but there exists a logical association between the segments belonging to any
level. Mostly, there exists a many-to-many logical association between any of the two
segments.
• We called graphs the logical associations between the segments. Therefore, this model
replaces the hierarchical tree with a graph-like structure, and with that, there can more
general connections among different nodes.
• It can have M: N relations i.e, many-to-many which allows a record to have more than
one parent segment.

20. Cont…
• Here, a relationship is called a set, and each set is made up of at least 2 types of
record which are given below:
i. An owner record that is the same as of parent in the hierarchical model.
ii. A member record that is the same as of child in the hierarchical model.

21. Example 1
In the above figure, member TWO has only one owner ‘ONE’ whereas member FIVE has
two owners i.e, TWO and THREE. Here, each link between the two record types represents
1 : M relationship between them. This model consists of both lateral and top-down
connections between the nodes. Therefore, it allows 1: 1, 1 : M, M : N relationships among
the given entities which helps in avoiding data redundancy problems as it supports
multiple paths to the same record.

22. Example 2
• In this figure, we can see that the
subject is the child class and student
and degree are the parent classes.
• So, the subject has two parent classes.
STUDENT has one child and the
Degree class also have one child.
• This kind of relationship among
entities represents the network
model.

23. Advantages
• It is fast data access with a network model.
• The network model allows creating more complex and more strong queries as
compared to the database with a hierarchical database model. A user can execute
a variety of database queries when selecting the network model.
• Sometimes, the network model is used to build computer network systems.
• The network model is considered as an enhancement to the hierarchical database
model.

24. Disadvantages
• The network model is a very complex database model, so the user must be very
familiar with the overall structure of the database.
• Updating the database is a quite difficult and boring task. We need the help of
the application programs that are being used to navigate the data.

25. Network model VS Hierarchical model VS Relational model:
Network Data Model Hierarchical Data Model Relational Data Model
Pointers or links are used to
express the relationship between
records.
The relationship between
records is of the parent-child
type
A relation(that contains a key for
each record involved in the
relationship) is used to represent
the relationship between
records.
It is possible to implement the
Many to many relationships.
Many to many relationships
cannot be expressed in
Hierarchical Data Model
It is easy to implement Many to
many relationships.
No problem of inconsistency
exists in the Network model.
The data inconsistency is
possible when we update or
delete some records.
Its needs to maintain Data
integrity and consistency by
maintaining the database
Normalization

26. Network Data Model Hierarchical Data Model Relational Data Model
Record relationship implementation
is quite complex due to the use of
pointers.
The method of implementing the
record relationships is;
· Simple
· Natural
· straightforward
The use of a key or composite key
field plays a role in making the
process easy for the implementation
of relationships.
In-Network model record relations
are physical.
The record relations are physical in
the Hierarchical data model.
Data is organized logically in the
form of rows and columns and
stored in the table.
The relational model does not
maintain a physical connection
among records.
Searching for a record is easy since
there are multiple access paths to a
data element.
Searching for a record is very
difficult because we can retrieve a
child only after going through its
parent record.
A unique, indexed key field is used
to search for a data element in a
relation.
The network model is useful for
representing such records that have
many to many relationships.
The hierarchical Data Model is
useful only when there is some
hierarchical character in the
database.
The relational model is useful for
representing most of the real-world
objects and relationships among the
objects.

27. AI database model - frame data structure
• Frame data structure used to represent a building design element. This frame describes the
location, type, cost, material, scheduled work time, etc. for a particular concrete footing.
• A frame is a general purpose data representation scheme in which information is arranged
in slots within a named frame.
• Slots may contain lists, values, text, procedural statements (such as calculation rules),
pointers or other entities. Frames can be inter-connected so that information may
be inherited between slots. The Figure illustrates a set of inter-connected frames used to
describe a building design and construction plan.
• Object oriented data representation is similar in that very flexible local arrangements of data
are permitted. While these types of data storage organizations are active areas of research,
commercial database systems based on these organizations are not yet available.

29. THANK YOU