process_descriptions13.ppt

Agenda

 _{Policy Review (again)}  _{Announcements}

 _{Review Chapter 8 material – DFD}  _{Review Chapter 9 material – ERD}

 _{Chapter 10 material – Process Descriptions}  _{Break – 15 minutes}

 _{Group Work}

Policy Review

 _{Absence should be documented}

 _{Arriving to meetings on time is an important}

aspect of professional conduct

 _{Extremely casual behavior can no longer be}

tolerated

 _{If you have conflicts or other business, simply}

ask to be excused

 _{Our time together must be productive}

 _{If we are not productive, classroom activities}

Announcements

 _{The IT Club has arranged for a guest speaker}

 Informal presentation regarding Software

Industry in BiH

 _{http://www.infostudio.ba}

 Saturday November 29th at 12:00  RSVP to [email protected]  Question and Answer Session

 _{PMI Meeting was small but productive}

Chapter 8 – Review

 _{Data flow diagrams illustrate how data moves}

through a system

 _{Data flow diagrams capture:}

 External entities  Sources

 Sinks

 Processes

 Files or Data stores

Chapter 8 & 9 – Review

 _{Data flow diagrams illustrate how data moves}

through a system

 _{Data flow analysis is used to model system}

flows

 _{Entity Relationship analysis is used to model}

system data

 If you use both models, they should use names

consistently

 Each model can help to develop and

Chapter 9 – Review

 _{Entity Relationship Analysis uses three}

major abstractions to describe data:

 Entities

 Relationships  _Attributes

 _{Entity Relationship Model represents}

Chapter 9 – Review

 _{Entity: a distinct object in a system}

 _{Entity Set: a component in an E-R diagram}

that represents a set of entities with the same properties

 _{Relationship: one interaction between one}

or more entities

 _{Relationship Set: a component in an E-R}

Chapter 9 – Review

 _{Attribute: a property of a set in an E-R model}  _{Identifier: a set of properties whose values}

identify a unique object in an object set

PERSONS

PERSON-ID

NAME

Chapter 9 – Review

 Cardinality_{: The number of relationships in}

which one entity can appear

Chapter 9 - Review

 _{DFD can suggest what to include in an E-R}

Diagram

 External entities can be modeled by an entity

set

Chapter 10 – Process Description

 _{DFD and ERD models are graphical models for}

systems

 Convenient for high-level design items  Easy to understand

 Not convenient for specifying processes in detail

 _{Defining processes in detail requires language}

 Natural language is an option for higher-level

items

 Natural language can be ambiguous

Chapter 10 – Process Description

 _{Scripting processes in Data Flow Diagrams}

 Structured English  Tight English

 _{Decision Tables}  Decision Trees

 _{Block structured language is a way of}

Chapter 10 – Structured English

IF credit limit exceeded THEN

IF customer has bad payment history THEN refuse credit

ELSE

IF purchase is above $200 THEN refuse credit

Chapter 10 – Structured English

 add PERSONS-SALARY to TOTAL-SALARY

 _{Structured English logic}

 REPEAT, WHILE, DO, IF, THEN, ELSE, FOR, etc.

 _{Grouping imperative sentences}

 BEGIN and END are used to group imperatives

 _Decisions

 IF, THEN, ELSE clauses determine branching

 _Repetition

Chapter 10 – Decision Tables

 _{Decision Tables are excellent for describing}

complex business logic

 Conditions record the logical possibilities

 Actions record the specific tasks to be

Chapter 10 – Decision Tables

Condition s

Account Type P P T T

Activity Type W D W D

Actions Add to account x x

Subtract from account x x

Add 1 to trade withdrawal x

Add 1 to personal withdrawal x

Add 1 to trade deposits x

Add 1 to personal deposits x

Chapter 10 – Decision Tables

 _{Decision Tables and Rules Engines}

 Rules engines can enforce business rules

 Rules engines accept decision tables as input  _{A convenient technique for externalizing}

business logic

 _{DROOLS is an open source rules engine that}

works with decision tables

User Requirements Example

 _{User must be able to login}

 _Username  Password

 _{If username/password combination is correct,}

then refresh webpage and display user’s home page

 _{If username/password combination is incorrect,}

then refresh webpage and display error page

 _{If user is an administrator, display link to}

Technical Requirements Example

 _{Expected number of users: 100}

 _{MySQL database will meet our needs for user}

storage

 _{PHP will meet our needs for Web Site}

 _{We do not expect heavy load of use so we can}

disregard scalability issues

 _{Performance issues will be handled with database}

tuning

 _{These technical requirements meet tight budget}

guidelines because both are free

Structured English - DFD 1.1

Receive Username / Password from form SELECT USER-ID FROM USER-SECURITY WHERE USERNAME = ‘Username’

AND PASSWORD = ‘Password’ IF RECORD COUNT = 1

THEN RETURN USER-ID ELSE

Capturing Business Logic

 _{These techniques are designed to capture}

business logic

 _{Business Logic defines the rules for}

decision-making in business

 _{Presentation Logic defines the Graphical User}

Interface and its rules and screen flows

 _{Database Layer concerns itself with the}

Break

15 minute break

Group Work: Technical Requirements

 _{Revise requirements based on:}

 Feedback from previous class

 Fill in additional functionality where needed  _{Add technical details such as:}

 Number of users supported  Technology required

 Scalability and Performance requirements  Availability requirements

 _{Revised requirements with technical details}