Java IoT Authors: Stackify Blog, Yeshim Deniz, Pat Romanski, Matt Lonstine, Glenda Sims

Related Topics: Java IoT

Java IoT: Article

Three Sources of a Solid Object-Oriented Design

Design heuristics, scientifically proven OO design guidelines, and the world beyond the beginning

Object-oriented design is like an alloy consisting of a solid grounding in the object-oriented (OO) approach and implementing the best OO practices heavily laced with how to sidestep the OO pitfalls. The design process isn't only a matter of applying basic OO principles. One should go further and achieve a reasonable tradeoff between OO design principles and applicable design patterns. This article will discuss the relationship between three sources of a solid OO design and offer a starting point to understanding what is, in effect, a complex process. It will also serve as a review for experienced designers.

The OO Design Pyramid

When developers first turn to object-oriented development, they try to grasp the basics. It may take several project lifetimes. Getting a full sense of object orientation is a big shift in people's minds, especially for those who come from the procedural world. Such principles are like ABC books since they define the foundation of the OO world.

Once people get a sense of the basic principles, they start feeling the power of the OO approach. In our experience this is a dramatic moment for every OO designer and developer. The euphoria of possessing a powerful methodology can make them feel completely self-sufficient and they stop and don't try for perfection. It takes time to realize that there are significant issues beyond the basics that can be found in the accumulated wisdom of the OO developer community and are expressed in a set of design heuristics and scientifically proven OO design guidelines. Some OO designers jump to using design patterns everywhere like a cookie recipe. Although design patterns are important and useful tools in building OO systems, they're just templates that define a common design language and significantly improve design quality, when properly used.

To build contemporary real-world enterprise-class systems, OO designers should (a) be proficient in basic OO principles, (b) master the principles of OO design, and (c) understand design patterns. Otherwise the chance of design flaws and total cost of system ownership increases. And, with growing adoption of Service Oriented Architecture (SOA), the robustness of the SOA services can depend directly on the solidity of the OO design of underlying components.

The pyramid in Figure 1 represents three sources of a solid OO design. It also defines a systematic view of design and uncovers dependencies between these sources.

Now let's discuss each level of this pyramid from an architectural and design point of view. Of course there's no way to explain these topics completely in such short article, but we'll try to highlight the necessity of paying attention to the dependencies and their impact on the quality of OO design.

Basic OO principles

The first level of the OO design pyramid is formed by a set of basic OO principles.

The most basic OO principles include encapsulation, inheritance, and polymorphism. Along with abstraction, association, aggregation, and composition, they form the foundation of the OO approach. These basic principles rest on a concept of objects that depicts real-world entities such as, say, books, customers, invoices, or birds. These classes can be considered templates for object instantiation, or object types. In other words, class specifies what an object can do (behavior) and defines patterns for its data (state). Modeling the real world in terms of an object's state and behavior is the goal of the OO approach. In this case, state is represented by a set of object attributes, or data, and behavior is represented by the object's methods.

Now we'll discuss the application of basic OO principles to modeling.

Encapsulation encloses data and behavior in a programming module. Encapsulation is represented by the two close principles of information hiding and implementation hiding. Information hiding restricts access to the object data using a clearly defined "interface" that hides the internal details of the object's structure. For each restricted class variable, this interface appears as a pair of "get" and "set" methods that define read-and-write access to the variable. Implementation hiding defines the access restrictions to the object methods also using a clearly defined interface that hides the internal details of object implementation and exposes only the methods that comprise object behavior. Both information and implementation hiding serve the main goal - assuring the highest level of decoupling between classes.

Inheritance is a relationship that defines one entity in terms of another. It designates the ability to create new classes (types) that contain all the methods and properties of another class plus additional methods and properties. Inheritance combines interface inheritance and implementation inheritance. In this case, interface inheritance describes a new interface in terms of one or more existing interfaces, while implementation inheritance defines a new implementation in terms of one or more existing implementations. Both interface inheritance and implementation inheritance are used to extend the behavior of a base entity.

Polymorphism is the ability of different objects to respond differently to the same message. Polymorphism lets a client make the same request of different objects and assume that the operation will be appropriate to each class of object. There are two kinds of polymorphism - inheritance polymorphism, which works on an inheritance chain, and operational polymorphism, which specifies similar operations for non-related out-of-inheritance classes or interfaces. Because inheritance polymorphism lets a subclass (subtype) override the operation that it inherits from its superclass (supertype), it creates a way to diversify the behavior of inherited objects in an inheritance chain, while keeping their parent-objects intact. Polymorphism is closely related to inheritance as well as to encapsulation.

Naturally, some OO principles are controversial in the sense that they contradict one another. For example, to be able to inherit from a class, one should know the internal structure of that class, while encapsulation's goal is exactly the opposite - it tries to hide as much of the class structure as possible. In real life the tradeoff between these two principles is a fine line that can't be established without stepping up to the next level in the design pyramid.

OO Design Principles and Heuristics

OO design principles and heuristics form the second level in OO design pyramid.

There are about a dozen OO design principles and four dozens OO design heuristics identified over the years by OO evangelists such as Grady Booch, Bertrand Meyer, Robert C. Martin, Barbara Liskov, and others. OO design principles define the most common scientifically derived approaches for building robust and flexible systems. These approaches proved to be the best tools in solving numerous OO design issues that can't be captured by fundamental OO principles.

The class structure and relationships group consists of the following design principles: the Single Responsibility Principle (SRP), the Open/Closed Principle (OCP), the Liskov Substitution Principle (LSP), the Dependency Inversion Principle (DIP), and the Interface Segregation Principle (ISP).

The Single Responsibility Principle specifies that class should have only one reason to change. It's also known as the cohesion principle and dictates that class should have only one responsibility, i.e., it should avoid putting together responsibilities that change for different reasons.

The Open/Closed Principle dictates that software entities should be open to extension but closed to modification. Modules should be written so that they can be extended without being modified. In other words, developers should be able to change what the modules do without changing the modules' source code.

The Liskov Substitution Principle says that subclasses should be able to substitute for their base classes, meaning that clients that use references to base classes must be able to use the objects of derived classes without knowing them. This principle is essentially a generalization of a "design by contract" approach that specifies that a polymorphic method of a subclass can only replace its pre-condition by a weaker one and its post-condition by a stronger one.

Dependency Inversion Principle says high-level modules shouldn't depend on low-level modules. In other words, abstractions shouldn't depend on details. Details should depend on abstractions.

The Interface Segregation Principle says that clients shouldn't depend on the methods they don't use. It means multiple client-specific interfaces are better than one general-purpose interface.

More Stories By Gene Shadrin

Gene Shadrin is an enterprise architect with 17 years of software development experience, including object-oriented analysis, design, architecture, and development of real-life enterprise Java systems. He is a Sun Certified Enterprise Architect, PMP, and consults government and Fortune 500 organizations. Gene can be contacted at [email protected]

Third Annual International Conference of Open systems. Moscow, Russia 1996. Thesis of lecture
Client-Server Technology Journal. Russia, 1996, 3-4 (double). ?PowerBuilder - Open Tool for Client-Server Computing? article.
Database Management Systems Journal. Russia, 1996, 5-6 (double). ?PowerBuilder - Open Tool for Complex Distributed Client-Server Computing? article.
?PowerBuilder: Developer?s Guide? Book. Translation from English. Russia, 1997, MIR Publishing-house (400 pages)
Database Management Systems Journal. Russia, 1997, 5-6 (double). "PFC Basics" article

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.

@ThingsExpo Stories
DX World EXPO, LLC, a Lighthouse Point, Florida-based startup trade show producer and the creator of "DXWorldEXPO® - Digital Transformation Conference & Expo" has announced its executive management team. The team is headed by Levent Selamoglu, who has been named CEO. "Now is the time for a truly global DX event, to bring together the leading minds from the technology world in a conversation about Digital Transformation," he said in making the announcement.
"Space Monkey by Vivent Smart Home is a product that is a distributed cloud-based edge storage network. Vivent Smart Home, our parent company, is a smart home provider that places a lot of hard drives across homes in North America," explained JT Olds, Director of Engineering, and Brandon Crowfeather, Product Manager, at Vivint Smart Home, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
SYS-CON Events announced today that Conference Guru has been named “Media Sponsor” of the 22nd International Cloud Expo, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. A valuable conference experience generates new contacts, sales leads, potential strategic partners and potential investors; helps gather competitive intelligence and even provides inspiration for new products and services. Conference Guru works with conference organizers to pass great deals to gre...
The Internet of Things will challenge the status quo of how IT and development organizations operate. Or will it? Certainly the fog layer of IoT requires special insights about data ontology, security and transactional integrity. But the developmental challenges are the same: People, Process and Platform. In his session at @ThingsExpo, Craig Sproule, CEO of Metavine, demonstrated how to move beyond today's coding paradigm and shared the must-have mindsets for removing complexity from the develop...
In his Opening Keynote at 21st Cloud Expo, John Considine, General Manager of IBM Cloud Infrastructure, led attendees through the exciting evolution of the cloud. He looked at this major disruption from the perspective of technology, business models, and what this means for enterprises of all sizes. John Considine is General Manager of Cloud Infrastructure Services at IBM. In that role he is responsible for leading IBM’s public cloud infrastructure including strategy, development, and offering m...
"Evatronix provides design services to companies that need to integrate the IoT technology in their products but they don't necessarily have the expertise, knowledge and design team to do so," explained Adam Morawiec, VP of Business Development at Evatronix, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
To get the most out of their data, successful companies are not focusing on queries and data lakes, they are actively integrating analytics into their operations with a data-first application development approach. Real-time adjustments to improve revenues, reduce costs, or mitigate risk rely on applications that minimize latency on a variety of data sources. In his session at @BigDataExpo, Jack Norris, Senior Vice President, Data and Applications at MapR Technologies, reviewed best practices to ...
Widespread fragmentation is stalling the growth of the IIoT and making it difficult for partners to work together. The number of software platforms, apps, hardware and connectivity standards is creating paralysis among businesses that are afraid of being locked into a solution. EdgeX Foundry is unifying the community around a common IoT edge framework and an ecosystem of interoperable components.
Large industrial manufacturing organizations are adopting the agile principles of cloud software companies. The industrial manufacturing development process has not scaled over time. Now that design CAD teams are geographically distributed, centralizing their work is key. With large multi-gigabyte projects, outdated tools have stifled industrial team agility, time-to-market milestones, and impacted P&L stakeholders.
"Akvelon is a software development company and we also provide consultancy services to folks who are looking to scale or accelerate their engineering roadmaps," explained Jeremiah Mothersell, Marketing Manager at Akvelon, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
"IBM is really all in on blockchain. We take a look at sort of the history of blockchain ledger technologies. It started out with bitcoin, Ethereum, and IBM evaluated these particular blockchain technologies and found they were anonymous and permissionless and that many companies were looking for permissioned blockchain," stated René Bostic, Technical VP of the IBM Cloud Unit in North America, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Conventi...
In his session at 21st Cloud Expo, Carl J. Levine, Senior Technical Evangelist for NS1, will objectively discuss how DNS is used to solve Digital Transformation challenges in large SaaS applications, CDNs, AdTech platforms, and other demanding use cases. Carl J. Levine is the Senior Technical Evangelist for NS1. A veteran of the Internet Infrastructure space, he has over a decade of experience with startups, networking protocols and Internet infrastructure, combined with the unique ability to it...
22nd International Cloud Expo, taking place June 5-7, 2018, at the Javits Center in New York City, NY, and co-located with the 1st DXWorld Expo will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud ...
"Cloud Academy is an enterprise training platform for the cloud, specifically public clouds. We offer guided learning experiences on AWS, Azure, Google Cloud and all the surrounding methodologies and technologies that you need to know and your teams need to know in order to leverage the full benefits of the cloud," explained Alex Brower, VP of Marketing at Cloud Academy, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clar...
Gemini is Yahoo’s native and search advertising platform. To ensure the quality of a complex distributed system that spans multiple products and components and across various desktop websites and mobile app and web experiences – both Yahoo owned and operated and third-party syndication (supply), with complex interaction with more than a billion users and numerous advertisers globally (demand) – it becomes imperative to automate a set of end-to-end tests 24x7 to detect bugs and regression. In th...
"MobiDev is a software development company and we do complex, custom software development for everybody from entrepreneurs to large enterprises," explained Alan Winters, U.S. Head of Business Development at MobiDev, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
Coca-Cola’s Google powered digital signage system lays the groundwork for a more valuable connection between Coke and its customers. Digital signs pair software with high-resolution displays so that a message can be changed instantly based on what the operator wants to communicate or sell. In their Day 3 Keynote at 21st Cloud Expo, Greg Chambers, Global Group Director, Digital Innovation, Coca-Cola, and Vidya Nagarajan, a Senior Product Manager at Google, discussed how from store operations and ...
"There's plenty of bandwidth out there but it's never in the right place. So what Cedexis does is uses data to work out the best pathways to get data from the origin to the person who wants to get it," explained Simon Jones, Evangelist and Head of Marketing at Cedexis, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
SYS-CON Events announced today that CrowdReviews.com has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5–7, 2018, at the Javits Center in New York City, NY. CrowdReviews.com is a transparent online platform for determining which products and services are the best based on the opinion of the crowd. The crowd consists of Internet users that have experienced products and services first-hand and have an interest in letting other potential buye...
SYS-CON Events announced today that Telecom Reseller has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. Telecom Reseller reports on Unified Communications, UCaaS, BPaaS for enterprise and SMBs. They report extensively on both customer premises based solutions such as IP-PBX as well as cloud based and hosted platforms.