ITDB1201:System Analysis and Design

ITDB1201:System Analysis and Design
Detail Analysis and Design Chapter 3 Prepared by: Marian Malig-on

Prepared by: Marian Malig-on
Data Modeling Create models for the system to design Conceptual data modeling are used in various phases of SDLC Prepared by: Marian Malig-on

Systems Development Life Cycle
Database Development Process Enterprise modeling Project Identification and Selection Conceptual data modeling Project Initiation and Planning Analysis Logical Design Logical database design Physical database design and definition Physical Design Implementation Database implementation Maintenance Database maintenance Prepared by: Marian Malig-on

ENTITY RELATIONSHIP DIAGRAM (ERD) Prepared by: Marian Malig-on

Entity-Relationship Diagram
It is a detailed, logical, and graphical representation of the data for an organization. The ER Diagram is: 1) a model of entities in the business environment 2) the relationships associations among those entities 3) The attributes or properties of both the entities and their relationships. Prepared by: Marian Malig-on

Entity-Relationship Model
STUDENT Entity - person, place, object, event, concept (often corresponds to a row in a table) Attribute - property or characteristic of an entity (often corresponds to a field in a table) Relationship – link between entities (corresponds to primary key-foreign key equivalencies in related tables) Name Registers Prepared by: Marian Malig-on 2

Entity An entity is a person, place, object, event, or concept in the user environment. Examples : Person: EMPLOYEE, STUDENT, PATIENT Place: STATE, REGION, COUNTRY, BRANCH Object: MACHINE, BUILDING, AUTOMOBILE, PRODUCT Event: SALE, REGISTRATION, RENEWAL Concept: ACCOUNT, COURSE, WORK CENTER Prepared by: Marian Malig-on

Entity Type Is a collection of entities that share common properties or characteristics Example: Since entity is an object, USE simple NOUN to name an entity type. USE capital letters in an E-R diagram, the name PLACED inside a rectangle. Prepared by: Marian Malig-on

Entity Instance or Instance
It is a single occurrence of an entity type. An entity type is described just once in a data model, but many instances of that entity type may be represented. Prepared by: Marian Malig-on

Attributes It is a property or characteristic of an entity that is of interest to the organization Each entity type has a set of attributes associated with it. Examples: STUDENT: Student_ID, Student_Name, Address, Phone_Number, Major AUTOMOBILE: Vehicle_ID, Color, Weight, Horsepower EMPLOYEE: Employee_ID, Employee_Name, Address, Skill Prepared by: Marian Malig-on

When naming attribute: Use NOUN with initial capital letter followed by lower case letters. In E-R diagram: Attribute is placed its name inside the rectangle that represents the associated entity. Prepared by: Marian Malig-on

In E-R diagram: If using drawing tools like Microsoft Visio, attributes are listed within the entity rectangle under the entity name. Or, Student_ID Student_Name Student_Address STUDENT Student_Campus_Phone Prepared by: Marian Malig-on

Candidate Key Is an attribute (or combination of attributes) that uniquely identifies each instance of an entity type. Examples : A Candidate key for STUDENT entity type might be Student_ID A candidate key for EMPLOYEE is Employee_ID; Second is the combination of Employee_Name and Address Prepared by: Marian Malig-on

Some entities may have more than one candidate key. Example: one candidate key for EMPLOYEE is Employee_ID, second is combination of Employee_Name and Address If more than one candidate key is involved, the designer must choose one of the candidate keys as identifier. Prepared by: Marian Malig-on

Identifiers Is a candidate key that has been selected to be used as the unique characteristic for an entity type. Rules for choosing identifiers Choose a candidate key that will not change its value over the life Example : Employee Name and address Prepared by: Marian Malig-on

2) Choose a candidate key such that for each instance of the entity, the attribute is guaranteed to have valid values and not be null. 3) Avoid the use of so-called intelligent keys, whose structure indicates classifications, locations, and other entity properties 4) Consider substituting single-attribute surrogate keys for large composite keys Example : Game_ID could be used for the entity GAME instead of combination of Home_Team and Visiting_Team. Prepared by: Marian Malig-on

The name of identifier is underlined in ER Diagram. STUDENT entity type using E-R notation: Prepared by: Marian Malig-on

The equivalent representation using Microsoft Visio is the following: Fig Identifier In the Visio notation, the primary key is listed immediately below the entity name with the notation PK, and the primary key is underlined. All required attributes (that is, an instance of STUDENT must have values for Student_ID and Name) are in bold Prepared by: Marian Malig-on

Sample E-R Diagram Attributes Supplier_ID Supplier_Name Supplier_Address Prepared by: Marian Malig-on 3

Multivalued Attribute
May take on more than one value for each entity instance. Example : Skill is the multivalued attribute of Entity EMPLOYEE Prepared by: Marian Malig-on

Repeating Group - several attributes that repeats together
In ER Tools (Microsoft Visio), do not support multivalued attributes within an entity. A second approach is to separate the repeating data into another entity, called a weak entity, and then using a relationship link a weak entity to the regular entity. Prepared by: Marian Malig-on

Example EMPLOYEE has many DEPENDENT DEPENDENT associated many EMPLOYEE Prepared by: Marian Malig-on

Relationship A relationship is an association between the instances of one or more entity types that are of interest to the organization. Example : Many to Many Relationship Prepared by: Marian Malig-on

Figure 3-11a attribute of the relationship The relationship type is modeled as the diamond and lines between entity types Prepared by: Marian Malig-on 20

Degree The degree of a relationship is the number of entity types that participate in that relationship. Example : Degree two relationship (Since it has two entity) unary (degree one), binary (degree two), and ternary (degree three). Prepared by: Marian Malig-on

Unary Relationship Also called a recursive relationship Is a relationship between the instances of one entity type. Prepared by: Marian Malig-on

Binary Relationship Is a relationship between instances of two entity types. Types of Binary Relationship: Prepared by: Marian Malig-on

Ternary Relationship Is a simultaneous relationship among instances of three entity types. Prepared by: Marian Malig-on

Note: a relationship can have attributes of its own Prepared by: Marian Malig-on 24

Cardinalities in Relationships
The cardinality of a relationship is the number of instances of entity B that can (or must) be associated with each instance of entity A. Example : Prepared by: Marian Malig-on

Minimum and Maximum Cardinalities Minimum Cardinality : Is the minimum number of instances of entity B that may be associated with each instance of entity A. Example : The minimum number of DVD available for a movie is zero. Maximum Cardinality : Is the maximum number of instances of entity B that may be associated with each instance of entity A Example : The maximum number of DVD avaliable for a movie is >1 Prepared by: Marian Malig-on

Minimum cardinality – zero (a circle near the DVD) Maximum cardinality – many(crow’s foot notation near the DVD) Prepared by: Marian Malig-on

Cardinality Constraints
Cardinality Constraints - the number of instances of one entity that can or must be associated with each instance of another entity Minimum Cardinality. Examples? If zero, then optional If one or more, then mandatory Maximum Cardinality. Examples? The maximum number Prepared by: Marian Malig-on 29

Cardinalities Mandatory one Mandatory many Optional one Optional many 11 18 Prepared by: Marian Malig-on

Figure 3-17c Optional cardinalities with unary degree, one-to-one relationship Prepared by: Marian Malig-on 34

Maximum Cardinality Constraint
max cardinality constraint Prepared by: Marian Malig-on 41

Entities can be related to one another in more than one way Prepared by: Marian Malig-on 40

Activity Prepared by: Marian Malig-on

Example: Student Registration System of Salalah College of Technology
*Identify the ENTITIES *Identify the ATTRIBUTES of each entity? *Identify the RELATIONSHIPS of each entity? * What are its CARDINALITIES? Prepared by: Marian Malig-on

Entity-Relationship Model
STUDENT Entity - person, place, object, event, concept (often corresponds to a row in a table) Attribute - property or characteristic of an entity (often corresponds to a field in a table) Relationship – link between entities (corresponds to primary key-foreign key equivalencies in related tables) Name Registers Prepared by: Marian Malig-on 2

Data Dictionary Look up information about the entities, attributes, and relationships on the ERD. Data dictionary captures about each element. Example : Data Dictionary Description for Item Entity Item – This entity represents the items carried in inventory in the super market. Item PK Item_UPC Item_description Item_Price Item_Category Item_TaxStatus Prepared by: Marian Malig-on

Example : Data Dictionary Description for Item Attributes
Physical Name Data Type Notes Item_UPC Char(10) Item_UPC identifies the Item Product code Item_description Char(25) Item_description is name or description of the product Item_Price Decimal(10,2) Item_Price is Cost of the Item to the buyer Item_Category Char(15) Item_Category is type of product (grocery, dairy, meat) Item_TaxStatus Char(1) Item_TaxStatus is of Tax(taxable, not taxable) Prepared by: Marian Malig-on

Sample Data Dictionary
Field Name Data type Field size Constraints Description Customer _ ID Number 6 PK Contains the Customer_ID Customer_Name Text 20 Not Null Contains the Customer_Name of the customer Customer_Address 12 Not null Contains the Customer_Address Contact Number 8 Contains the Contact Number of customer E_mail Contains the E_mail of the customer Prepared by: Marian Malig-on

Example : Data Dictionary Description for Relationship
Prepared by: Marian Malig-on

Example without Normalization STUDENT TABLE S-ID S-Name S_Address Subject_Choice 401 Salim Raysut Science 402 Khalid Saadah Math 403 Mohammed Salalah 404 English What happens If we Update the Address? If we Insert a new student but student don’t chose a course yet ? If we Delete like student drops the subject? Prepared by: Marian Malig-on

Validating an Entity Relationship Diagram
Normalization is the process whereby a series of rules is applied to the logical data model to determine how well formed. A technique of organizing the data in the database. It is a multi step process that puts data into tabular form by removing duplicated data from the relation tables. Prepared by: Marian Malig-on

Purpose of Normalization Remove redundant (useless or repeated) data Make sure data dependencies make sense Example: data is logically stored Prepared by: Marian Malig-on

Normalization rule are divided into the following Normal forms:
First Normal Form -1NF Second Normal Form – 2NF Third Normal Form – 3NF Prepared by: Marian Malig-on

1NF - A logical data model is in first normal form (1NF) if it does not contain repeating attributes, which are attributes that capture multiple values for a single instance. Prepared by: Marian Malig-on

Sample of Table not in First Normal Form
Student Age Subject Khalid 15 Science, Math Salim 14 Math Mohammed 13 Prepared by: Marian Malig-on

Table in First Normal Form
Student Age Subject Khalid 15 Science Salim 14 Math Mohammed 13 Data Redundancy increases as there will be multiple rows added, but each row as a whole will be unique. Prepared by: Marian Malig-on

2NF - Second normal form (2NF) requires that all entities are in 1NF and contain only attributes whose values are dependent on the whole identifier (i.e., no partial dependency). Prepared by: Marian Malig-on

Table in Second Normal Form
Student Age Khalid 15 Salim 14 Mohammed 13 Student Subject Khalid Science Salim Math Mohammed There is Partial dependency Prepared by: Marian Malig-on

3NF - Third normal form (3NF) occurs when a model is in both 1NF and 2NF and none of the resulting attributes is dependent on non-identifier attributes (i.e., no transitive dependency). Finally , data model entities and attributes correspond to data stores and data flows on the process model. Prepared by: Marian Malig-on

Table in Third Normal Form
Student Table S_ID S_Name D_Birth Street City State Zip Prepared by: Marian Malig-on

Table in Third Normal Form
STUDENT Table S_ID S_Name D_Birth ADDRESS Table Zip Street City State Prepared by: Marian Malig-on

DATA FLOW DIAGRAM (DFD)
Prepared by: Marian Malig-on

DATA FLOW DIAGRAMS (DFD)
– graphical representation to show the flow of data within the system. - shows the processes in the system data are in motion and moving as a unit from one place in a system to another. Prepared by: Marian Malig-on

Purpose/Objective of DFD To provide a bridge between users and systems developers. Useful for analyzing existing (old) systems as well as proposed (new) systems Graphical: Remove thousands of words. Logical Representations: Modeling WHAT a system does, rather than physical model showing HOW it does it. Prepared by: Marian Malig-on

Systems Analyst understand the information requirements of users by conceptualizing How data moves in the company the processes or transformation that the data undergoes, and what the outputs are even if sample forms or hard data are provided. Prepared by: Marian Malig-on

2 CATEGORIES OF DFD LOGICAL DATA FLOW DIAGRAM Focuses on the business and how the business operates. It describes the events that happens and the data required and produced in each event. 2. PHYSICAL DATA FLOW DIAGRAM Shows how the system will be implemented. including the hardware, software, files and the people involved in the system. Prepared by: Marian Malig-on

Ideally, systems are developed by analyzing the current system (the current (old) logical DFD), then adding the features that the new system should include (the proposed logical DFD). Finally, the best methods for implementing the new system should be developed (the physical DFD). Prepared by: Marian Malig-on

Levels of Data Flow Diagram 1.) Context Flow Diagram or Level 0 2.) Diagram 0 or Level 1 3.) Child Diagram Level 2 Prepared by: Marian Malig-on

4 BASIC SYMBOLS OF DFD Symbol Meaning Example Source/Sink Or ENTITY STUDENT Double Square Prepared by: Marian Malig-on

An ENTITY/external entities is the origin and/ or source of data and it is considered to be external to the system. It may be a person, group, department, machine, or any system that either receives or originates (give) information or data. It can send data to or receive data from the system. Prepared by: Marian Malig-on

Each ENTITY is labeled with an appropriate name. It should be named with a NOUN. The same entity may be used more than once on a given DFD to avoid crossing data flow lines. Prepared by: Marian Malig-on

4 BASIC SYMBOLS OF DFD Symbol Meaning Example 2.1 PROCESS Create Student Record Rectangle with Rounded Corners OR Prepared by: Marian Malig-on

When modeling the data processing of a system, it doesn’t matter whether a process is performed manually or by a computer. A PROCESS are actions performed on data so they are transformed, stored or distributed. A PROCESS means that some action or group of actions take place. Prepared by: Marian Malig-on

When naming a Process: A clear name makes it easier to understand what the process is completing. 1.) Assign the name of the whole system when naming a high-level process (Context Diagram or Level 0). Ex. Student Management System, Payroll System 1.1To name a major subsystem, use name like: Student Registration subsystem Attendance subsystem, Student Marking subsystem Prepared by: Marian Malig-on

When naming a Process: 2.) For detailed processes (Diagram 0/Level 1), use a verb-adjective-noun format Example: Register Student Timetable Compute Student Mark Compute Sales Tax, Verify Customer Accounts Status A process must also be given a unique identifying number indicating its level within the diagram. Prepared by: Marian Malig-on

4 BASIC SYMBOLS OF DFD Symbol Meaning Example DATA STORE D1 Student Master Open-ended Rectangle OR DATA STORE Prepared by: Marian Malig-on

A DATA STORE is data at rest. It may represent one of many different physical locations for data: manual store: file folder or filing cabinet, notebook computerized file or database. It is simply showing a depository for data that allows addition and retrieval (opening) of data. Data store might contain data about customers, students, customer orders Prepared by: Marian Malig-on

4 BASIC SYMBOLS OF DFD Symbol Meaning Example DATA FLOW New Student Information Arrow Prepared by: Marian Malig-on

A DATA FLOW shows that information is being passed from or to a process. It shows movement from one point to another, with the head of the arrow pointing toward the data’s destination. Since an arrow represents data about a person, place, or thing, it too should be described with a NOUN Prepared by: Marian Malig-on

Data flows occur at the same time are presented through the use of parallel arrows. And more than one data flow noun phrase can appear on a single arrow as long as all of the flows on the same arrow move together as one package. Prepared by: Marian Malig-on

DATA FLOW A data flow cannot go directly back to the same process it leaves.. A data flow to a data store means update (delete or change). A data flow from a data store means retrieve or use. Prepared by: Marian Malig-on

Legal and Illegal Data Flows
All data flows must begin and/or end with a process. Data cannot legally flow directly from a source to a destination or between a source/destination and a data store unless they pass through an intermediate process. Process / Entity Process / Entity Prepared by: Marian Malig-on

Process Process / Process / DATA STORE Process / DATA STORE Prepared by: Marian Malig-on

Entity Entity X Entity X DATA STORE X Entity DATA STORE X DATA STORE DATA STORE Prepared by: Marian Malig-on

DON’T’ BREAK THE RULES WHEN DRAWING DATA FLOW DIAGRAMS X 2 Data flows should not split into two or more different data flows 1 3 Prepared by: Marian Malig-on

X 2 Processes need to have at least one input data flow and one output data flow Prepared by: Marian Malig-on

DEVELOPING DFDs To begin a DFD, break the organization’s system narrative into a list with four categories: external entity data flow process data store Once a basic list of data elements has been compiled, begin drawing a Context Diagram. Prepared by: Marian Malig-on

Problem Analysis and DFD Draw the DFD for a distance education university. The enrolment process works as follows: Example 1 : Students send in an application form containing their personal details and their desired course. The university checks that the course is available and that the student has necessary academic qualifications. If the course is available the student is enrolled in the course, and the university confirms the enrolment by sending a confirmation letter to the student. If the course is unavailable the student is sent a rejection letter. Prepared by: Marian Malig-on

Read the problem description carefully looking for: people/organizations/things that supply information to or use information from the system => external entities (EE) actions/doing words/verbs => Processes (P) movement/exchange of information/data between external entities to processes, and processes to processes => data flows (DF) store/record information/data => data stores(DS) Prepared by: Marian Malig-on

2. It often helps to walk through the system in its logical sequence; e.g. starting with an external entity (source), add data flows, processes and data stores as the data provided by the system. A student (EE) sends in an application form (DF) containing their personal details, and their desired course The university checks (P) that the course is available. If the course is available the student is enrolled (P) in the course, and the university confirms (P) the enrolment by sending a confirmation letter (DF) that they are registered for the course to the student. Or if the course is unavailable the student is sent a rejection letter (DF). Prepared by: Marian Malig-on

STEPS IN CONSTRUCTING DFDs Start with the Context Diagram Identify the functions to be performed 3. Show the information flow between functions and identify data stores and external entities 4. Repeatedly elaborate on the DFD ( bottom up and top down ) Prepared by: Marian Malig-on

CONTEXT DIAGRAMS or Level 0 It provides the most general view of an information system. Has a single process symbol representing the whole system, entities and data flow. a bird’s eye view of data movement in the system Prepared by: Marian Malig-on

STEPS IN CONSTRUCTING CONTEXT DIAGRAMS 1. First, place a single process symbol at the center of the page. The symbol represents the entire information system, and you identify it as Process 0. 2. Then, place the external entities around the process and use data flows to connect the entities to the central process. 3. Do not show any data stores in a context diagram because data stores are internal to the system. Prepared by: Marian Malig-on

How to make the context flow diagram?
Entity 1 System Name Input A Entity 3 Output C Input B Entity 2 Prepared by: Marian Malig-on

Student Administration System
Example: External entity - Student Process - Student Administration process application Data Flows - Application Form, Confirmation/Rejection Letter Student Administration System Student Application details Confirmation/rejection details Prepared by: Marian Malig-on

Inventory Control Department Sample CFD Back ordered item Customer Order Purchasing System Customer Order Shipped Order Customer Customer Billing Statement New Customer Info Item # of Description Item Information Accounting Warehouse Accts. Receivable Report Order Picking List Order Goods Prepared by: Marian Malig-on

DIAGRAM 0 or Level 1 It is more detailed than the context diagram. “exploding the diagrams”, because the inputs, processes and outputs are exploded and is evident with data stores and new lower level data flows - It is the explosion of the Context Diagram and may include up to nine processes. - Each process is numbered with an integer, generally starting from the upper left-hand corner of the diagram and working toward the lower right hand corner. - The major data stores of the system (representing master files) and all external entities are included. Prepared by: Marian Malig-on

Examples of Diagram 0 Prepared by: Marian Malig-on

CHILD DIAGRAMS Creating Child Diagrams (More Detailed Levels)- each process on Diagram 0 may in turn be exploded to create a more detailed child diagram. The process on Diagram 0 that is exploded is called parent process, and the diagram that results is called the child diagram. The primary rule for creating for creating child diagrams, vertical balancing, dictates that a child diagram cannot produce output or receive input that the parent process does not also produce or receive. Prepared by: Marian Malig-on

Examples of Child Diagrams Prepared by: Marian Malig-on

Sample Context Flow Diagram
Management Management Video Purchase System Management Reports Video Purchase System Video Information Video Rental System Rental Receipt Customer Customer New Customer Info Customer Video Rental card Video Rental Item Monthly Bonus Letter Customer ID Payment Yearly Bonus Letter Returned Video Information Accounting This example is based from Film Magic Video Rental Stores Total Cash Received Prepared by: Marian Malig-on

Sample Diagram 0 Rental Receipt 1 Rent Video Items Produce Management Reports 2 Video Rental Item Rental Information Management Reports Management Customer Customer ID Cash Transaction Payment Cash Transaction Summarize Cash Received 4 Total Cash Received Video Purchase System Video Information Accounting Customer Record D1 Customer Customer Record Check In Customer Video Return 3 Customer Returned Video Information Customer D1 Customer Customer Record New Customer Information Customer Record Customer Record Yearly Bonus Letter 7 Produce Yearly Bonus Letter 5 Add New Customer 6 Produce Monthly Bonus Letter Customer Video Rental Card Monthly Bonus Letter Prepared by: Marian Malig-on

Sample Child Diagram of Process 1 in Diagram 0 Video Rental Item Rental Information Payment 1.1 Get Video Record 1.2 Get Customer Payment Video Information Cash Transaction Rental information 1.4 Produce Customer Report Rental Receipt Rental information 1.3 Update Customer Record Rental Information D1 Customer Customer Record 1.5 Find Customer Record Customer Name and Address Customer ID Not found error Customer Record Prepared by: Marian Malig-on

ITDB1201:System Analysis and Design

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ITDB1201:System Analysis and Design

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