IAD 2263: System Analysis and DesignChapter 7: Designing System

Databases, Interfaces and Security

Content– Designing Databases– Designing the User Interface– Designing the System Interfaces,

Controls and Security

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Databases and Database

Management Systems• Databases (DB) – integrated collections of

stored data that are centrally managed and controlled

• Database management system (DBMS) – system software that manages and controls access to database

• Databases described by a schema – description of structure, content, and access controls

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Database Models• Impacted by technology changes

since 1960s• Model types

– Hierarchical – Network– Relational– Object-oriented

• Most current systems use relational or object-oriented data models

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Relational Databases• Relational database management

system (RDBMS) organizes data into tables or relations

• Tables are two dimensional data structures– Tuples – rows or records – Fields – columns or attributes

• Tables have primary key field(s) that can be used to identify unique records

• Keys relate tables to each other

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Partial Display of Relational Database

Table

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Designing Relational Databases

• Create table for each entity type

• Choose or invent primary key for each table

• Add foreign keys to represent one-to-many relationships

• Create new tables to represent many-to-many relationships

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Designing Relational Databases (continued)

• Define referential integrity constraints

• Evaluate schema quality and make necessary improvements

• Choose appropriate data types and value restrictions (if necessary) for each field

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Relationship Between Data in Two Tables

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RMO Entity-Relationship Diagram

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Representing Relationships

• Relational databases use foreign keys to represent relationships

• One-to-many relationship– Add primary key field of “one” entity type

as foreign key in table that represents “many” entity type

• Many-to-many relationship– Use the primary key field(s) of both

entity types – Use (or create) an associative entity

table to represent relationship

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Entity Tables with Primary Keys

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Database Normalization• Normal forms minimize data redundancy

– First normal form (1NF) – no repeating fields or groups of fields

– Functional dependency – one-to-one relationship between the values of two fields

– 2NF – in 1NF and if each non-key element is functionally dependent on entire primary key

– 3NF – in 2NF and if no non-key element is functionally dependent on any other non-key element

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Object-Oriented Databases

• Direct extension of OO design and programming paradigm

• ODBMS stores data as objects • Direct support for method storage,

inheritance, nested objects, object linking, and programmer-defined data types

• Object Definition Language (ODL)– Standard language for describing structure

and content of an object database

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Designing Object Databases

• Determine which classes require persistent storage

• Define persistent classes

• Represent relationships among persistent classes

• Choose appropriate data types and value restrictions (if necessary) for each field

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RMO Domain Model Class

Diagram

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One-to-Many Relationship Between Customer and Order

Classes

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Views of Stored Data

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Relationships• Relationships are represented with foreign

keys • Foreign key values serve same purpose as

object identifiers in ODBMS• 1:M relationship – add primary key field of

class on “one” side of the relationship to table representing class on “many” side

• M:M relationship – create new table that contains primary key fields of related class

tables and attributes of the relationship itself

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Identifying System Interfaces

• System interfaces are broadly defined as inputs or outputs with minimal or no

human intervention– Inputs from other systems (messages, EDI)– Highly automated input devices such as

scanners– Inputs that are from data in external databases– Outputs to external databases– Outputs with minimal HCI– Outputs to other systems– Real-time connections (both input and output)

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Full Range of Inputs and Outputs

Figure 15-1

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Designing System Outputs

• Determine each type of output

• Make list of specific system outputs required based on application design

• Specify any necessary controls to protect information provided in output

• Design and prototype output layout

• Ad hoc reports – designed as needed by user

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Defining the Details of System Outputs

• Type of reports– Printed reports– Electronic displays– Turnaround documents

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Sample Bar Chart and Pie Chart Reports

Figure 15-17

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Formatting Reports• What is objective of report?

• Who is the intended audience?

• What is media for presentation?

• Avoid information overload

• Format considerations include meaningful headings, date of information, date report

produced, page numbers

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Objectives of Integrity Controls

• Ensure that only appropriate and correct business transactions occur

• Ensure that transactions are recorded and processed correctly

• Protect and safeguard assets of the organization

– Software

– Hardware

– Information

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Points of Security and Integrity Controls

Figure 15-18

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Input Integrity Controls• Used with all input mechanisms

• Additional level of verification to help reduce input errors

• Common control techniques– Field combination controls– Value limit controls– Completeness controls– Data validation controls

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Designing Security Controls

• Security controls protect assets of organization from all threats

– External threats such as hackers, viruses, worms, and message overload attacks

• Security control objectives

– Maintain stable, functioning operating environment for users and application systems (24 x 7)

– Protect information and transactions during transmission outside organization (public carriers)

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Security for Access to Systems

• Used to control access to any resource managed by operating system or network

• User categories– Unauthorized user – no authorization to

access– Registered user – authorized to access system– Privileged user – authorized to administrate

system

• Organized so that all resources can be accessed with same unique ID/password

combination

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Users and Access Roles to

Computer Systems

Figure 15-20

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Managing User Access• Most common technique is user ID / password• Authorization – Is user permitted to access?

• Access control list – users with rights to access• Authentication – Is user who they claim to be?• Smart card – computer-readable plastic card

with embedded security information• Biometric devices – keystroke patterns,

fingerprinting, retinal scans, voice characteristics

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Data Security• Data and files themselves must be secure

• Encryption – primary security method– Altering data so unauthorized users cannot view

• Decryption – Altering encrypted data back to its original state

• Symmetric key – same key encrypts and decrypts

• Asymmetric key – different key decrypts• Public key – public encrypts; private decrypts

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Symmetric Key Encryption

Figure 15-22

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Asymmetric Key Encryption

Figure 15-23

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Digital Signatures and Certificates

• Encryption of messages enables secure exchange of information between two

entities with appropriate keys • Digital signature encrypts document with

private key to verify document author• Digital certificate is institution’s name

and public key that is encrypted and certified by third party

• Certifying authority– VeriSign or Equifax

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Secure Transactions• Standard set of methods and protocols for

authentication, authorization, privacy, integrity

• Secure Sockets Layer (SSL) renamed as Transport Layer Security (TLS) – protocol for

secure channel to send messages over Internet

• IP Security (IPSec) – newer standard for transmitting Internet messages securely

• Secure Hypertext Transport Protocol (HTTPS or HTTP-S) – standard for transmitting Web pages securely (encryption, digital signing,

certificates)

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