Systems Design

We we came from… Planning Analysis Design Implementation Identify Problem/Value. Feasibility Analysis. Project Management. Understand as-is system. Identify Improvements. Develop concept for the to-be system. Use Cases. DFDs. ERDs.

Systems Design Planning Analysis Design Implementation Develop technical specifics for to-be system. Design Strategies. Physical DFD. Physical ERD. Infrastructure Plan. Interface Structure. Interface Standards. Interface Template. Interface. Evaluate.

Design Strategy: Outsource or not? Factors Favoring Make Customized Products Customized Products Confidentiality of Data & Business Confidentiality of Data & Business Reduce Vendor Risk Reduce Vendor Risk Increased Ease of Development Increased Ease of Development Ease of Internal Adaptation of Software Ease of Internal Adaptation of Software Develop Leading-Edge Competence Develop Leading-Edge Competence Factors Favoring Buy Access to Specialized Skills Access to Specialized Skills Cost Cost Staff Utilization Staff Utilization Reduced Recruitment & Training Reduced Recruitment & Training High Standards of Control & Security High Standards of Control & Security Proliferation of Information Services Proliferation of Information Services

Outsource? Check SDLC Systems Implementation Product: Operational System Systems Implementation Product: Operational System Systems Investigation Product: Feasibility Study Systems Investigation Product: Feasibility Study Systems Analysis Product: Functional Requirements Systems Analysis Product: Functional Requirements Systems Design Product: System Specifications Systems Design Product: System Specifications Systems Maintenance Product: Improved System Systems Maintenance Product: Improved System Understand the Business Problem or Opportunity Develop an Information System Solution Implement the System Solution Highly Structured OR... Most time spent here.

Infrastructure Plan: Centralized or Distributed? Dumb

Infrastructure Plan: Centralized or Distributed?

Tiers in a Client-Server Network Tier One: Main Server Tier Two: Clients of Tier One, Servers to Tier Three Tier 3: Clients of Tier Two

How are infrastructures established? A quick look at Telecomm Basics. Let’s talk:

I want to talk to someone else:

They want to talk to someone else etc., etc.!!!:

CO Switch Along comes the switch. In Public Switched Telephone Network (PSTN, or sometimes “POTS”), this is basically the EXCHANGE (last 4 digits) (aaa) ppp-XXXX

Switches in the same LATA (“Local Access and Transport Area”) are distinguished by PREFIX (first 3 digits). (aaa) PPP-xxxx

Calls that cross a LATA boundary are distinguished by AREA CODE (numbers in parentheses). These are “long distance” calls. (AAA) ppp-xxxx LATA boundary

PSTN These calls are all “circuit switched” Dedicated line. Comes from voice requirements. Contrasts the Internet and Web which is “packet switched”. Messages can travel many paths. Comes from data requirements.

Company A Company B Company D Company C W1 W9 W12 W10 W2 W11 W6 W7 W8 W3 W4 W5 Internet Backbone from Company A to Company D:

Company A Company B Company D Company C W1 W9 W12 W10 W2 W11 W6 W7 W8 W3 W4 W5 Internet Backbone from Company A to Company D:

Company A Company B Company D Company C W1 W9 W12 W10 W2 W11 W6 W7 W8 W3 W4 W5 Internet Backbone from Company A to Company D: broken into packets, that travel the best path.

Company A Company B Company D Company C W1 W9 W12 W10 W2 W11 W6 W7 W8 W3 W4 W5 Internet Backbone from Company A to Company D: packets reassembled at the other end. Of course, TCP/IP is the dominant packet switching protocol.

Company A Company B Company D Company C W1 W9 W12 W10 W2 W11 W6 W7 W8 W3 W4 W5 Internet Backbone PSTN Consumer 1 Consumer 2 WAN Companies A-D are all connected to the Internet, Companies B & D are trading partners and are connected through a WAN, and Consumers 1 & 2 are connected to the PSTN, and also to the Internet through the PSTN. A "W" in a box represents a Web server (thus, Company D's Web server is "W12"). Putting it all together.

Company A Company B Company D Company C W1 W9 W12 W10 W2 W11 W6 W7 W8 W3 W4 W5 Internet Backbone PSTN Consumer 1 Consumer 2 WAN firewall, fiber, frame relay, TCP/IP, DSL, and modem?

PSTN MTSO “Mobile Telephone Switching Office” Other Base Stations “Cells” Base Stations Mobile Units What about wireless?

Telecommunications Infrastructure Multiplexer Gateway Modem Earth Station Earth Station Coaxial cable Fiber optic cable Host Computer Microwave Link Microwave Link Satellite Regional Office Wireless LAN Satellite Central Office End User Workstation Satellite

Infrastructure Plan You must understand the available local, regional, national, and international infrastructure to make your plan!!! Your plan determines your “options” for years to come!!! Don’t base your plan simply on your immediate needs.

Systems Design Planning Analysis Design Implementation Develop technical specifics for to-be system. Design Strategies. Physical DFD. Physical ERD. Infrastructure Plan. Interface Structure. Interface Standards. Interface Template. Interface. Evaluate.

Interface The connection between the system and the rest of the world (whether humans or other systems). “The interface **IS** the system.”

Principles for User Interface Design Layout Content awareness Aesthetics User experience Consistency Minimal user effort

Layout Concepts The screen is often divided into three boxes Navigation area (top) Status area (bottom) Work area (middle) Information can be presented in multiple areas Like areas should be grouped together

More Layout Concepts Areas and information should minimize user movement from one to another Ideally, areas will remain consistent in Size Shape Placement for entering data Reports presenting retrieved data

Minimize Effort Three clicks rule Users should be able to go from the start or main menu of a system to the information or action they want in no more than three mouse clicks or three keystrokes

User Interface Design Process

User Interface Design Process: Five Step Process

Interface Evaluation Methods Heuristic evaluation Compare design to checklist Walkthrough evaluation Team simulates movement through components Interactive evaluation Users try out the system Formal usability testing Expensive Detailed use of special lab testing

User Interface Design Components The navigation mechanism provides the way for users to tell the system what to do The input mechanism defines the way the system captures information The output mechanism defines the way the system provides information to users or other systems

Navigational Design: Basic Principles Assume users Have not read the manual Have not attended training Do not have external help readily at hand All controls should be clear and understandable and placed in an intuitive location on the screen.

Navigational Design: Basic Principles Prevent mistakes Limit choices Never display commands that can’t be used (or “gray them out”) Confirm actions that are difficult or impossible to undo Simplify recovery from mistakes Use consistent grammar order

Input Design: Basic Principles The goal is to simply and easily capture accurate information for the system Reflect the nature of the inputs Find ways to simplify their collection “Garbage in, garbage out” Financial Example

Online versus Batch Processing Online processing immediately records the transaction in the appropriate database Batch processing collects inputs over time and enters them into the system at one time in a batch Batch processing simplifies data communications and other processes, but means that inventory and other reports are not accurate in real time

Capture Data at the Source Reduces duplicate work Reduces processing time Decreases cost Decreases probability of error

Interface Design Choices You have recently been promoted to IS manager of a fast-food chain. Your first assignment is to speed up the drive-through line, using a more modern method of user interface (currently drivers speak their orders to an employee of your chain). Your order process is PC-based. Discuss possible options.

Source Data Automation Can be obtained by using the following technologies: bar code readers optical character recognition magnetic stripe readers smart cards Web voice recognition?

Output Design: Basic Principles Understand report usage Reference or cover-to-cover? Frequency? Real-time or batch reports? Manage information load All needed information, no more Minimize bias