DBMS Interfaces & Database Models

1.Menu-Based Interfaces for Web Clients or Browsing :

    These interfaces present the user with lists  of  options,  called  menus,  that lead the user through the formulation of a request. Menus do the   specific commands and syntax of a query language; rather, the query is composed step by step by picking options from a menu that is displayed by the system.

      Pull-down menus are popular used in Web-based user interfaces. They are also often used in browsing interfaces, which allow a user to look through the contents of a database in an exploratory and unstructured manner.

2. Forms-Based Interfaces :

A forms-based interface displays a form to each user. Users can fill out all of the form entries  to insert new data, or they fill out only certain entries, in which the DBMS will retrieve matching data for the remaining entries.

Forms are usually designed and programmed for naive users as interfaces to transactions.Some systems have utilities that define a form by letting the end user interactively construct a sample form on the screen.

A)Graphical User Interfaces :

A graphical User interface (GUI) typically displays a schema to the user in diagrammatic form. The user can then specify a query by manipulating the diagram.

In many cases, GUIs utilize both menus and forms. Most GUIs  use  a pointing device, such as a mouse, to pick certain parts of the displayed schema diagram.

B) Interfaces for the DBA :

        Most database systems contain privileged commands that can be used only by the DBA's staff. These include commands for  creating  accounts,  setting system parameters, granting account authorization, changing a schema, and reorganizing the storage structures of a database.

Database Models:

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. While the Relational Model is the most widely used database model, there are other models too:
·       Hierarchical Model
·       Network Model
·       Entity-relationship Model
·       Relational Model

Hierarchical Models:

This database model organises data into a tree-like-structure, with a single root,  to  which   all   the   other   data   is   linked.   The   heirarchy   starts   from the Root data, and expands like a tree, adding child nodes to the parent nodesstem. 

In this model, a child node will only have a single parent node. This model efficiently describes many real-world relationships like index of a book, recipes etc. In hierarchical model, data is organised into tree-like structure with one one- to-many relationship between two different types of data, for example, one department can have many courses, many professors and of-course many students.

Network Model:

This is an extension of the Hierarchical model. In this model data is organised more like a graph, and are allowed to have more than one parent node.

In this database model data is more related as more relationships are established in this database model. Also, as the data is more related, hence accessing the data is also easier and fast. This database model was used to map many-to-many data relationships.

This was the most widely used database model, before Relational Model was introduced.

Entity-relationship Model:

In this database model, relationships are created by dividing object of interest into entity and its characteristics into attributes.

Different entities are related using relationships. E-R Models are defined to represent the relationships into pictorial form to make it easier for different stakeholders to understand.

This model is good to design a database,  which  can  then  be  turned  into tables in relational model(explained below).

Let's  take an example,  If   we   have   to   design   a   School   Database, then Student will    be    an entity with attributes name,     age,     address     etc. As Address is generally complex, it can be another entity with attributes street name, pincode, city etc, and there will be a relationship between them.

Relational Model:

In this model, data is organised in two-dimensional tables and the relationship is maintained by storing a common field.

This model was introduced by E.F Codd in 1970, and  since  then  it  has been the most widely used database model, infact, we can say the only database model used around the world.

The basic structure of data in the relational model is  tables.  All  the information related to a particular type is stored in rows of that table,hence tables are also known as relations in relational model.