TweetFollow Us on Twitter

September 93 - OOA/OOD

OOA/OOD

Mark J. Klocke

A structured engineering approach (methodology) is required to support the development of complex software systems. A methodology consists of a required set of development deliverables and formal guidelines for producing the deliverables. This article will present object-oriented analysis and design deliverables with examples from a Time Reporting System application. An automated and integrated tool set is a crucial component of a successful software project. Examples in this article were created with MacA&D, a commercial Computer Aided Software Engineering (CASE) tool from Excel Software.

Object-oriented methods offer improvements in quality, managing complexity, and ultimately reducing the development and maintenance cost of software projects. The project challenges to overcome are to flatten the object-oriented learning curve, apply objects to your domain, and achieve re-use of your domain objects. Several object-oriented analysis and design (OOA & OOD) methods, such as the Coad/Yourdon, Rumbaugh, Shlaer/Mellor, and Booch, are currently being used to address these challenges and improve the development of applications. Coupled with CASE tools these methods can provide an integrated, streamlined approach to software development (see Figure 1: Object-oriented Analysis and Design Deliverables).

In the Time Reporting System example, we boil down the myriad of OOA and OOD techniques to their essential elements; these elements are class diagrams, object (instance and communication) diagrams, and their supporting state and flow diagrams. In addition, we will use screen prototyping to express the sample application's user interface. Diagrams are integrated with a global data dictionary and requirement database to simplify model associations for development and maintenance. Other text deliverables such as the project specification, test information, and code will not be reviewed at this time. Chronologically, the deliverables in Figure 1 are produced top down, and left to right, with information in the data dictionary being supplied from the other documents.

Development Deliverables Overview

The Requirements Database integrates models by common requirements, providing traceability throughout the development and maintenance of the application. Requirements may be collected portions of a text document, or entered according to a user defined template.

Screen prototyping can be used to analyze the essential elements of the user interface prior to the formal design process. Menus, buttons, data fields, and other interface items may be used to quickly generate a sample interface and interactively browse through connected screens and dialogs.

A class diagram illustrates object classes and structures using a variety of symbols, line styles and line terminations. For each object class, attributes (data) and operations (algorithms) are identified and defined.

Some objects have an associated life cycle represented by specific states or modes in which the object can exist. A transition from one state to another will occur when a specific event takes place. Object life cycles can be represented by state transition diagrams or tables.

Data Flow Diagrams are used within some methodologies to model application context and object interfaces (data and control). Data Flow Diagrams are used more extensively for functional decomposition in Structured Analysis, and will only be touched upon briefly for this example.

While a class diagram is great for illustrating the static structure of classes from which objects are instantiated, it reveals little about how objects interact with each other. An object diagram is used to show how each mechanism in the design works by passing messages between object operations.

To ensure consistency and completeness, the various views of a software design must be integrated. A data dictionary integrates all the diagramming views into a common repository of information and provides detailed definitions for items used on diagrams.

Requirement Database

Historical data shows that defects which occur during the requirement definition phase are much more costly to correct than those introduced during the later design or implementation phases of development. This effect is compounded as the size of the project and development team grows. Requirement defects include missing, incomplete, ambiguous, or non-implemented requirements. Using a requirement database can reduce the risk and cost of requirement defects.

A requirement database is simply a list of requirement statements each uniquely identified by a name or number. Parent and child references are associated with each requirement statement to provide traceability. A parent reference identifies the source of a requirement, while a child reference targets a deliverable such as a design diagram or test procedure which satisfies the requirement. Transforming user requirements, concepts, and ideas into a detailed design ready for implementation is an iterative modeling process.

Each requirement statement is an unambiguous, testable fact (typically by multiple test cases) about a condition or capability needed by a user to solve a problem or achieve an objective. Requirements are processing, information, performance, or capacity statements about the system under design. System and product requirements are typically derived from market demands, quality, reliability, performance, and safety considerations.

The requirement database provides concrete links between requirement statements and other deliverables of the development process. Traceability provides a clear picture of how each requirement is satisfied and quick assessment of the impact of requirement changes.

To illustrate requirement statements and the other forms of modeling to follow, consider the analysis and design of a Time Reporting System. Here is a requirement used to specify this project:

NAME: Report$Employee$Sort
PARENT: FOREIGN TimeReports.Spec
DEFINITION: Employee reports shall be sorted by job title or
            alphabetically by last name.
CHILD: FORM TimeReports.Form Main Screen 
ERD TimeReports.ERD TRS 
OBJECT TimeReports.OBJ Generate Employee Reports 
FOREIGN Reports.TDS EmployeeSortTest 

Requirement statements can be written using a formal structure or as simple sentences as we have used here. References provide traceability to origin (parent) and development deliverables (children).

Screen Prototype

Screen prototyping can be an effective means of exposing requirements and achieving consensus on user interface early in a project. A screen prototype is simply a set of interconnected user screens containing interface elements such as data entry fields, buttons, menus, text and graphics. MacAnalyst supports dynamic interactive screen prototypes which allow users to provide constructive feedback on the user interface before starting the software design process.

Using the Time Reporting System example, two screens and a menu representing its user interface are shown below. Upon access (login) to the Time Reporting System, the main menu is displayed (see Figure 2-Time System Startup Screen).

The screen was created by defining the pull-down menus and menu commands. The following screens which use the same menu commands 'clone' the definition from the startup screen. In the Time Reporting System, the user selects commands from the File, Edit, and Report pull-down menus (see Figure 3-Interactively Browsing Screens). In Browse mode (interactive), selecting the New Time Sheet command from the File menu brings up the New Time Sheet window (see Figure 4-New Time Sheet Screen).

Like other views in the modeling process, interface items on the screens of a prototype are integrated with other CASE models via the data dictionary and requirement database.

Class Diagram

The class diagram shows each object class and its associated attributes and operations. Structures between classes such as inheritance are represented on the class diagram. In our Time Reporting System example, a fictitious third party class library (called SimpleApp) is used for the user interface and file manipulation. A new Coad/Yourdon style class library (TimeReports) was created for our time reports application.

The SimpleApp class named "Object" is at the root of the inheritance tree. The class "Application" is a subclass of "Event Handler." Subclasses, or the general/specific relationship, is shown by the rounded triangle. Aggregation, or whole/part relationships, are shown by a triangle such as "ListOfItems" being part of a "Document." The "Application" class will have attributes "TimeSheetsList," "ProjectList," and "EmployeeList" (which are references to instances of the "ListOfItems" container class), and operations "MainEventLoop," "DoMenu-Command," and "VerifyLogin," plus attributes and operations inherited from its parent classes (see Figure 5-Coad/Yourdon Style Class Diagram Portion of SimpleApp, and Figure 6-Coad/Yourdon Style Class Diagram - Time Reporting System).

Organizing data and algorithms into classes is an important part of analysis and design. Good candidate classes can often be chosen from a general description of the problem domain as in our example of Employee, Manager, Project, and TimeSheet. Design is an iterative process requiring many refinements as more is understood about the system under study. Object communication diagrams described below are an excellent way of revealing the inadequacies of a first draft class diagram by exposing missing or inconsistent attributes and operations.

Like other views of the system, the class diagram is an integrated part of the CASE repository. For example, within MacA&D, double-clicking on a Class object brings forward the Data Dictionary window and displays detailed information about that class including its attributes, operations and inherited classes. Detailed descriptions of each attribute and operation can be included in the dictionary.

State Transition Diagrams

Since objects may be dynamically allocated, real-time modeling techniques for state transitions and data/event flow can be used to detail each object. Data flow diagrams are used to provide a frame of reference, or context, for the system, and to provide another view of the objects abstract control and data interface.

Dynamically allocated objects have various states of operation, such as "Initialized," "Active," and "Failure Mode." The states of dynamic objects, often referred to as an object life-cycle, are modeled with a state transition diagram (STD).

State transition diagrams (STDs) and tables are a common modeling technique for expressing the finite states within a system or object, and events which can occur to cause a transition from one state to another. A state model can also express a list of actions which take place upon transition from one state to another.

In the Time Reporting System example, two states ("Active User" and "Active Admin") are detailed in subdiagrams. Upon initialization, a login dialog is presented. A correct login transitions service to one of two "Active" states and enables the menu commands. This is illustrated in Figure 7.

Object Communication Diagram

Object communication diagrams are used to show how mechanisms in the design work by passing messages between instantiated object classes. In our Time Reporting System example, five diagrams are sufficient to represent the new mechanisms of the Time System domain. Two of the seven original (SimpleApp) mechanisms for event handling were modified for our application. The Login and Project Reports mechanisms are shown.

After application initialization, the "VerifyLogin" operation of the Application invokes the iterate operation "EachItemDo" to verify the login EmployeeID with the Employee list IDs (see Figure 8-Object Communication Diagram - Login).

Now let's consider the mechanism of Generate Project Reports. In this mechanism, a menu Project Report command event is processed by the "Main Event Loop" which invokes the "ListInfoReport" operation with the requested project number. "ListInfoReport" iterates through the "TimeSheets" ListOfItems and if the project number matches the requested project number, the "TimeSheet" instances "Print" operation generates its portion of the report. When the search is complete Project notifies the Application instance (see Figure 9-Object Communication Diagram - Generate Project Reports).

Summary

This article presented an overview of object-oriented analysis and design techniques for software applications. A Requirements Database, Screen Prototypes, Class Diagrams, and Object Diagrams deliverables were presented. The diagrams were created using a CASE tool, MacA&D. In addition to easy creation and editing of diagrams, MacA&D allows designers to integrate the different modeling views of their project and provide easy navigation between these models.

Producing these deliverables within a CASE tool automates steps of the development process, such as error checking and producing reports. For example, when you have completed the class diagrams of a design, use the Relation Specifications report to automatically produce a complete text narrative of your design directly from the diagrams. Verification and balancing reports can check for literally hundreds of inconsistencies or omissions between diagrams and dictionary information within seconds. Together OOA and OOD techniques coupled with CASE technology can provide a powerful method for software development.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Kodi 17.1. - Powerful media center tool...
Kodi (was XBMC) is an award-winning free and open-source (GPL) software media player and entertainment hub that can be installed on Linux, OS X, Windows, iOS, and Android, featuring a 10-foot user... Read more
Bookends 12.8 - Reference management and...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Bookends uses the cloud to sync reference libraries on all the Macs you use.... Read more
Apple iTunes 12.6 - Play Apple Music and...
Apple iTunes lets you organize and stream Apple Music, download and watch video and listen to Podcasts. It can automatically download new music, app, and book purchases across all your devices and... Read more
Default Folder X 5.1.4 - Enhances Open a...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click on... Read more
Amazon Chime 4.1.5587 - Amazon-based com...
Amazon Chime is a communications service that transforms online meetings with a secure, easy-to-use application that you can trust. Amazon Chime works seamlessly across your devices so that you can... Read more
CrossOver 16.2 - Run Windows apps on you...
CrossOver can get your Windows productivity applications and PC games up and running on your Mac quickly and easily. CrossOver runs the Windows software that you need on Mac at home, in the office,... Read more
Adobe Creative Cloud 4.0.0.185 - Access...
Adobe Creative Cloud costs $19.99/month for a single app, or $49.99/month for the entire suite. Introducing Adobe Creative Cloud desktop applications, including Adobe Photoshop CC and Illustrator CC... Read more
MegaSeg 6.0.2 - Professional DJ and radi...
MegaSeg is a complete solution for pro audio/video DJ mixing, radio automation, and music scheduling with rock-solid performance and an easy-to-use design. Mix with visual waveforms and Magic... Read more
Bookends 12.8 - Reference management and...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Bookends uses the cloud to sync reference libraries on all the Macs you use.... Read more
Adobe Creative Cloud 4.0.0.185 - Access...
Adobe Creative Cloud costs $19.99/month for a single app, or $49.99/month for the entire suite. Introducing Adobe Creative Cloud desktop applications, including Adobe Photoshop CC and Illustrator CC... Read more

The best deals on the App Store this wee...
Deals, deals, deals. We're all about a good bargain here on 148Apps, and luckily this was another fine week in App Store discounts. There's a big board game sale happening right now, and a few fine indies are still discounted through the weekend.... | Read more »
The best new games we played this week
It's been quite the week, but now that all of that business is out of the way, it's time to hunker down with some of the excellent games that were released over the past few days. There's a fair few to help you relax in your down time or if you're... | Read more »
Orphan Black: The Game (Games)
Orphan Black: The Game 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Dive into a dark and twisted puzzle-adventure that retells the pivotal events of Orphan Black. | Read more »
The Elder Scrolls: Legends is now availa...
| Read more »
Ticket to Earth beginner's guide: H...
Robot Circus launched Ticket to Earth as part of the App Store's indie games event last week. If you're not quite digging the space operatics Mass Effect: Andromeda is serving up, you'll be pleased to know that there's a surprising alternative on... | Read more »
Leap to victory in Nexx Studios new plat...
You’re always a hop, skip, and a jump away from a fiery death in Temple Jump, a new platformer-cum-endless runner from Nexx Studio. It’s out now on both iOS and Android if you’re an adventurer seeking treasure in a crumbling, pixel-laden temple. | Read more »
Failbetter Games details changes coming...
Sunless Sea, Failbetter Games' dark and gloomy sea explorer, sets sail for the iPad tomorrow. Ahead of the game's launch, Failbetter took to Twitter to discuss what will be different in the mobile version of the game. Many of the changes make... | Read more »
Splish, splash! The Pokémon GO Water Fes...
Niantic is back with a new festival for dedicated Pokémon GO collectors. The Water Festival officially kicks off today at 1 P.M. PDT and runs through March 29. Magikarp, Squirtle, Totodile, and their assorted evolved forms will be appearing at... | Read more »
Death Road to Canada (Games)
Death Road to Canada 1.0 Device: iOS Universal Category: Games Price: $7.99, Version: 1.0 (iTunes) Description: Get it now at the low launch price! Price will go up a dollar every major update. Update news at the bottom of this... | Read more »
Bean's Quest Beginner's Guide:...
Bean's Quest is a new take on both the classic platformer and the endless runner, and it's free on the App Store for the time being. Instead of running constantly, you can't stop jumping. That adds a surprising new level of challenge to the game... | Read more »

Price Scanner via MacPrices.net

Updated iPad Price Trackers
Scan our Apple iPad (and iPod touch) Price Trackers for the latest information on sales, bundles, and availability on systems from Apple’s authorized internet/catalog resellers. We update the... Read more
12-inch 32GB Space Gray iPad Pro on sale for...
B&H Photo has 12″ Space Gray 32GB WiFi Apple iPad Pros on sale for $50 off MSRP including free shipping. B&H charges sales tax in NY only: - 12″ Space Gray 32GB WiFi iPad Pro: $749 $50 off... Read more
2.6GHz Mac mini on sale for $559, $140 off MS...
Guitar Center has the 2.6GHz Mac mini (MGEN2LL/A) on sale for $559 including free shipping. Their price is $140 off MSRP, and it’s the lowest price available for this model. Read more
SSD Speeder RAM Disk SSD Life Extender App Fo...
Fehraltorf, Switzerland based B-Eng has announced they are making their SSD Speeder app for macOS publicly available for purchase on their website. SSD Speeder is a RAM disk utility that prevents... Read more
iPhone Scores Highest Overall in Smartphone D...
Customer satisfaction is much higher among smartphone owners who use their device to operate other connected home services such as smart thermostats and smart appliances, according to the J.D. Power... Read more
Swipe CRM Free Photo-Centric CRM Sales DEal C...
Swipe CRM LLC has introduced Swipe CRM: Visual Sales 1.0 for iPad, an app for creating, managing, and sharing visually stunning sales deals. Swipe CRM is targeted to small-and-medium creative... Read more
13-inch 2.0GHz Apple MacBook Pros on sale for...
B&H has the non-Touch Bar 13″ 2.0GHz MacBook Pros in stock today and on sale for $150 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.0GHz MacBook Pro Space Gray (... Read more
15-inch Touch Bar MacBook Pros on sale for up...
B&H Photo has the new 2016 15″ Apple Touch Bar MacBook Pros in stock today and on sale for up to $150 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.7GHz Touch Bar... Read more
Apple’s iPhone 6s Tops Best-Selling Smartphon...
In terms of shipments, the iPhone 6s from Apple bested all competitors for sales in 2016, according to new analysis from IHS Markit, a world leader in critical information, analytics and solutions.... Read more
Logitech Rugged Combo Protective iPad Case an...
Logitech has announced its Logitech Rugged Combo, Logitech Rugged Case, and Logitech Add-on Keyboard for Rugged Case for Apple’s new, more affordable $329 9.7-inch iPad, a complete solution designed... Read more

Jobs Board

*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Fulltime aan de slag als shopmanager in een h...
Ben jij helemaal gek van Apple -producten en vind je het helemaal super om fulltime shopmanager te zijn in een jonge en hippe elektronicazaak? Wil jij werken in Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Fulltime aan de slag als shopmanager in een h...
Ben jij helemaal gek van Apple -producten en vind je het helemaal super om fulltime shopmanager te zijn in een jonge en hippe elektronicazaak? Wil jij werken in Read more
Starte Dein Karriere-Abenteuer in den Hauptst...
…mehrsprachigen Teams betreust Du Kunden von bekannten globale Marken wie Apple , Mercedes, Facebook, Expedia, und vielen anderen! Funktion Du wolltest schon Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.