PART VI: ANALYSIS AND DESIGN OF INFORMATION SYSTEM

DATABASE AND ER-DIAGRAM

DEFINITION OF DATABASE
A database is a structured collection of records or data that is stored in a computer system. The structure is achieved by organizing the data according to a database model. The model in most common use today is the relational model. Other models such as the hierarchical model and the network model use a more explicit representation of relationships.

Coherent collection of mutually data get bearings of an enterprise (business, institution instance or private ).

• Manufacturing business: production planning data, current production data, ordering data significant, etc.
• Hospital: patient data, doctor, nurse, etc.

DATABASE MANAGEMENT SYSTEM
A DBMS is a set of software programs that controls the organization, storage, management, and retrieval of data in a database. DBMS are categorized according to their data structures or types. It is a set of prewritten programs that are used to store, update and retrieve a Database. The DBMS accepts requests for data from the application program and instructs the operating system to transfer the appropriate data. When a DBMS is used, information systems can be changed much more easily as the organization's information requirements change. New categories of data can be added to the database without disruption to the existing system.


BIT, BYTE, FIELD

• A bit is a binary digit, taking a value of either 0 or 1. Binary digits are a basic unit of information storage and communication in digital computing and digital information theory.
• A byte is a bulk of bit that a sort. Or a byte is an ordered collection of bits, with each bit denoting a single binary value of 1 or 0. The byte most often consists of 8 bits in modern systems.
• Field is a group byte’s that a sort, in data basis utilized by attribute terminology.

ATTRIBUTE/FIELD
Constituting character or characteristic of an entity that provide detail explanations about that entity. A relationship can also have attribute.
Attribute example:

• UNIVERSITY STUDENT: NIM, NAME, ADDRESS
• CAR: NOMOR_PLAT, COLOR, TYPE, CC

ATTRIBUTE TYPES

• Single vs multivalue

Single --> just can be filled at most one point
Multivalue --> can be filled by more than one point with same type of

• Atomic vs is composition

Atomic --> indiscrete into smaller attribute
Composition --> constituting affiliate of some attribute which smaller

• Derived Attribute

attribute that its point gets resultant of other attribute point, for example --> resulting age of date attribute comes into the world.

• Null Value Attribute

Attribute that have no point for a record

• Mandatory Value Attribute

Attribute who shall have point


RECORD/TUPLE
Constituting a data row in a relationship. Consisting of collection attribute's where that attribute interactions to inform entity / comprehensive relationships.


ENTITY/FILE
File constitutes collection from record what do a sort and to have same element, attribute is with but variably data value's.

File type
In application proceedings, file can at category as follows:

• Parented file
• Transactions file
• Write-up file
• History file
• Protecting file
• Job file

DOMAIN
Domain constitutes group of point that is let for lies deep one or more attribute. Each attribute in a relation data base is defined as a domain.


DATA ELEMENT KEY
key is record's element that is used to find record that on access time or can also be utilized to identify each entity / record / the line.


KEY TYPES

• Super key constitutes one or more attribute of a table applicable to identify entity / record of unique ala table (are not all attribute can be super key ).

• Candidate key is super keys with minimal attribute. Candidate key may not contain attribute of candidate's the other so key table definitely super key but was obviously contrariwise.

• Primary keys

One of attribute from candidate keys to get is chosen / is determined as primary keys with three criterions as follows:

• that key is more natural to been utilized as basis
• that key is simpler
• that key its uniqueness indemnity bond

Alternate keys is attribute from candidate keys that don't be chosen becomes primary key.

• Foreign keys to constitute bungling attribute which point for primary to key on the other table. Foreign keys will happen at one particular relationship which have cardinality one to many (one to there are many) or many to many (there are many to a lot of). Foreign key. usually do ever be placed on table that aims to go to a lot of.

• External keys to constitute a lexical attribute (or lexical gathering attribute) one that its point do ever identify one object instance.

ERD (ENTITY RELATIONSHIP DIAGRAM)
ERD is a model network which utilize wording that is kept in abstractive system. The difference among DFD and ERD.

• DFD constitutes a logistic network model that will be performed by system.
• ERD constitutes data network model that emphasizes on structure and relationship is data.

ERD ELEMENTS

• ENTITY

On ER Entity's diagram is figured with square form long. Entity is aught something in real system and also abstract where data is kept or where exists data.

• Relationship

On ER diagram relationship can be figured by one lozenges. Relationship is subjective artless one be become among entity. In a general way given by name by says basic job so making easy to do its relationship perusal.

• Relationship Degree

are total entity who participated in one relationship. Degree that frequent being used on ERD

• Attribute

are character or characteristic of every entity and also relationship

• Cardinality

pointing out record optimum that relations can with entity on entity another one.



DEGREE RELATIONSHIP

• Unary Relationship

are model relationship that happening among entity what do come from same entity set.

• Binary Relationship

are model relationship that happening among 2 entity.

• ternary Relationship

constituting relationship among instance of 3 entity types unilateral.



CARDINALITY
Available 3 cardinality relationships which is

• One to One: Subjective zoom one to one stated with one instance on entity first, just has one relationship with one instance on entity secondly conversely.

• One to Many or Many To One: Subjective zoom one to there are many is same with many to one pending of tenor which that relationship is seen. To one instance on entity first gets to have a lot of relationship with instance on entity secondly, if contrariwise one instance on entity just secondly gets to have relationship with one instance on entity is first.

• Many To Many: happening if each instance on one entity has a lot of relationship with instance on another entity.

EXAMPLE OF CARDINALITY





NOTATION (DIAGRAM E R)
Symbol notation diagrammatically ER is :

1. Length square declare for entity gathering
2. Circle declares for attribute
3. Rhomb declares for relationship gathering
4. Lining as connecting as among relationship gathering with entity gathering and Entity Gathering with its attribute.

References:
http://en.wikipedia.org/wiki/Database
http://en.wikipedia.org/wiki/Database_management_system
http://en.wikipedia.org/wiki/Bit
http://en.wikipedia.org/wiki/Byte
slide presentation "Database and ER-Diagram" by Agus Sanjaya ER, S.Kom, M.Kom