Mgt 20600: IT Management & Applications Networks (cont.) Databases Thursday October 13, 2005

Reminders  Reading –For today  Fundamentals text, Chapter Three, Organizing Data and Information chapter –For the Thursday after break  Fundamentals text, Chapter 6, Information and Decision Support Systems  Homework –Database/DSS homework will be posted tomorrow –Due October 28 th: Friday after fall break  Exams –Medians of 58.6 (Section 3) and 59.5 (Section 4)  Nice work for many of you!  If you didn’t do as well as you like, still many hundreds of points to go in the course  Suggestions –Always do reading ahead of time, not just before exam –Always come to class –Take the homeworks seriously and review them before the exams –Come and see me and Christine for help with exam review  Next week: Fall break!

Telecommunications and Networks Elements of a Telecommunications System

Transmission Media Wired Transmission Media Types

Wired Media Types

Wireless Transmission Media Types  Radio Waves –Bluetooth  Short distances only  Relatively slow transmission speed  Developed for inter-device communications –Wi-Fi  Standard supports up to 54Mbps  Supports longer distances than bluetooth  Infrared –Signals sent as light waves –Short distance –Unobstructed line of sight  Microwave –High frequency radio signal –Capable of high-speed transmission –Unobstructed line of sight –Susceptible to interference  Cellular

Networks  Computer network: the communications media, devices, and software needed to connect two or more computer systems or devices  Network nodes: the computers and devices on the networks

Network Types  Personal area network (PAN)  Local area network (LAN)  Metropolitan area network (MAN)  Wide area network (WAN)  International network

Network Types A Typical LAN

Network Types A Wide Area Network Is the internet a wide area network?

Communications Software and Protocols  Communications software: software that provides a number of important functions in a network, such as error checking and data security –Network operating system (NOS) –Network management software –Communications protocol: a standard set of rules that controls a telecommunications connection  Example, TCP/IP protocol that underlies the Internet

The Internet  Internet: a collection of interconnected networks, all freely exchanging information  ARPANET –The ancestor of the Internet –A project started by the U.S. Department of Defense (DoD) in 1969

How the Internet Works  Data is passed in chunks called packets –Internet Protocol (IP)  Communications standard that enables traffic to be routed from one network to another as needed  Every computer attached to internet has an IP address –Transmission Control Protocol (TCP)  Widely used transport-layer protocol that is used in combination with IP by most Internet applications  In charge of communication session between two computers –Uniform Resource Locator (URL)  Assigned addresses for web servers and the web pages they provide

How the Internet Works Routing Messages over the Internet

Accessing the Internet Several Ways to Access the Internet

Internet Service Providers  Internet service provider (ISP): any company that provides individuals or organizations with access to the Internet –Most charge a monthly fee –Many ISPs and online services offer broadband Internet access through digital subscriber lines (DSLs), cable, or satellite transmission

Applications that run over the Internet  World Wide Web  Instant Messaging   File Transfer Protocol  Telnet  All of these are –Software applications –Designed for the internet –All assume your computer understands TCP/IP

The World Wide Web  Hypertext Transfer Protocol (HTTP): Protocol that web servers and browsers use to send requests and information  Hypertext Markup Language (HTML): the standard page description language for Web pages

Intranets and Extranets  Intranet –Internal corporate network built using Internet and World Wide Web standards and products –Used by employees to gain access to corporate information –Slashes the need for paper

Intranets and Extranets  Extranet –A network based on Web technologies that links selected resources of a company’s intranet with its customers, suppliers, or other business partners  Virtual private network (VPN) –Secure connection between two points across the Internet –Intranets and extranets often run over VPN’s

Internet Issues  Privacy –Spyware: hidden files and information trackers that install themselves secretly when you visit some Internet sites –Cookie: a text file that an Internet company can place on the hard disk of a computer system

Net Issues  Security –Cryptography: converting a message into a secret code and changing the encoded message back to regular text –Digital signature: encryption technique used to verify the identity of a message sender for processing online financial transactions –Firewall: a device that sits between an internal network and the Internet, limiting access into and out of a network based on access policies

Net Issues

Databases  A well-designed and well-managed database is an extremely valuable tool in supporting decision making  Databases are key corporate assets  Databases are the foundation for sophisticated analyses that provide business intelligence –What new products to design –How to market to particular customer groups –Which customer groups are the most profitable

Traditional Approach to Data Management Traditional approach: separate data files are created for each application Results in data redundancy (duplication) Data redundancy conflicts with data integrity

Database Approach to Data Management Database approach: pool of related data is shared by multiple applications Significant advantages over traditional approach

Advantages of Database Approach  Improved strategic use of data  Reduced data redundancy  Improved data integrity  Easier modification and updating  Data and program independence  Better access to data and information  Standardization of data access  A framework for program development  Better overall protection of the data  Shared data and information resources

Disadvantages of the Database Approach  More complexity  More difficult to recover from a failure  More expensive

Databases  Databases must contain –Accurate information –Right kinds of information –Current information –Information from all organizational functions

Database Data  Data regarding –Important entities  Customers  Suppliers  Transactions –Each entity will have a number of attributes about which you want to collect and store information  Customer address  Customer phone number  Customer account number

Entities, Attributes, Keys Entity: a generalized class of people, places, or things (objects) for which data is collected, stored, and maintained (Table and records) Attribute: a characteristic of an entity (fields) Data item: a value of an attribute (fields) Key: field(s) that identify a record Primary key: field(s) that uniquely identify a record

Hierarchy of Data Field: name, number, or characters that describe an aspect of a business object or activity Record: a collection of related data fields File: a collection of related records Database: a collection of integrated and related files

Data Modeling and the Relational Database Model  When building a database, consider: –Content: What data should be collected, at what cost? –Access: What data should be provided to which users, and when? –Logical structure: How should data be arranged to make sense to a given user? –Physical organization: Where should data be physically located?

Data Modeling  Building a database requires two types of design –Logical design  Shows an abstract model of how data should be structured and arranged to meet an organization’s information needs –Physical design  Fine-tunes the logical database design for performance and cost considerations

Data Modeling  Data model: a diagram of data entities and their relationships  Entity-relationship (ER) diagrams: data models that use basic graphical symbols to show the organization of and relationships between data

Data Modeling An Entity-Relationship (ER) Diagram for a Customer Order Database

The Relational Database Model  Relational model: all data elements are placed in two-dimensional tables (relations), which are the logical equivalent of files  In the relational model: –Each table represents a data entity –Each row of a table represents a specific instance of a data entity –Columns of the table represent attributes

The Relational Database Model A Relational Database Model