Welcome!

Java IoT Authors: Elizabeth White, Karyn Jeffery, Thanh Tran, Nate Vickery, Liz McMillan

Related Topics: Open Source Cloud, Java IoT, Industrial IoT, Microservices Expo, Microsoft Cloud, IoT User Interface

Open Source Cloud: Article

Abstractness vs Instability: A Neo4j Case Study

Discover Abstractness vs Instability graph

Robert C.Martin wrote an interesting article about a set of metrics that can be used to measure the quality of an object-oriented design in terms of the interdependence between the subsystems of that design.

Here's from the article what he said about the interdependence between modules:

What is it that makes a design rigid, fragile and difficult to reuse. It is the interdependence of the subsystems within that design. A design is rigid if it cannot be easily changed. Such rigidity is due to the fact that a single change to heavily interdependent software begins a cascade of changes in dependent modules. When the extent of that cascade of change cannot be predicted by the designers or maintainers the impact of the change cannot be estimated. This makes the cost of the change impossible to estimate. Managers, faced with such unpredictability, become reluctant to authorize changes. Thus the design becomes rigid.

And to fight the rigidity he introduce metrics like Afferent coupling, Efferent coupling, Abstractness and Instability.

Let's discover all these metrics and how they could be very useful to improve the design of applications. For that let's analyze Neo4j by JArchitect.

Neo4j is a robust transactional property graph database. Due to its graph data model, Neo4j is highly agile and blazing fast. For connected data operations, Neo4j runs a thousand times faster than relational databases.

And here's the dependency graph between all Neo4j jars

neo4j1

Neo4j contains many jars and all of them depend on neo4j-kernel, and to have more details about the weight of using each jar, The DSM (Dependency Structure Matrix) is a compact way to represent and navigate across dependencies between components.

neo4j6

As the matrix shows the neo4j kernel is heavily used by the other jars.

Afferent Coupling:
The number of types outside this project that depend on types within this project.

Let's execute the following CQLinq query to get the afferent coupling of Neo4j jars:

from p in Projects where !p.IsThirdParty select new { p,p.NbTypesUsingMe }

neo4j2

As discovered before the kernel is the more solicited by the other jars.

Efferent Coupling
The number of types outside this project used by types of this project.

from p in Projects where !p.IsThirdParty select new { p,p.NbTypesUsed }

neo4j3

The efferent coupling and afferent coupling could be applied also on packages and types. For example the efferent coupling for a particular type is the number of types it directly depends on. Types where TypeCe is very high are types that depend on too many other types. They are complex and in general have more than one responsibility.

Abstractness
The ratio of the number of internal abstract types (i.e abstract classes and interfaces) to the number of internal types. The range for this metric is 0 to 1, with A=0 indicating a completely concrete project and A=1 indicating a completely abstract project

A = Na / Nc

Where:

A = abstractness of a module
Zero is a completely concrete module. One is a completely abstract module.
Na = number of abstract classes in the module.
Nc = number of concrete classes in the module.

Let's take as example the neo4j-kernel-1.8.2 jar and search for all abstract types.

from t in Types where t.IsAbstract || t.IsInterface select new { t, t.NbLinesOfCode }

neo4j4

neo4j-kernel-1.8.2 has 1071 types so the Abstractness is equal to 233/1071 = 0.21755

To increase the abstractness of a project we have to add more abstract classes or interfaces.

Instability
The ratio of efferent coupling (Ce) to total coupling. I = Ce / (Ce + Ca). This metric is an indicator of the project's resilience to change. The range for this metric is 0 to 1, with I=0 indicating a completely stable project and I=1 indicating a completely instable project.

I = Ce/(Ce + Ca)
I represent the degree of instability associated with a project.
Ca represents the afferent coupling, or incoming dependencies, and
Ce represents the efferent coupling, or outgoing dependencies

Let's take as example a class where many other classes used it and it not use any other class. In this case this class is considered as stable for the following reasons:

- This kind of class depends upon nothing at all, so a change from a depended cannot ripple up to it and cause it to change. This characteristic is called “Independence”. Independent classes are classes which do not depend upon anything else.

- It's depended upon by many other classes. It became harder to make changes to it. And if we were to change it we would have to change all the other classes that depended upon it. Thus, there is a great deal of force preventing us from changing these classes, and enhancing their stability.

Classes that are heavily depended upon are called “Responsible”. Responsible classes tend to be stable because any change has a large impact.

Let's search for the more responsible types by executing the following CQLinq query

(from t in Types orderby t.NbTypesUsingMe descending, t.NbTypesUsed descending, t.NbBCInstructions descending select new { t, t.NbTypesUsingMe,t.NbTypesUsed})

neo4j5

The Expression class is the most popular one.

Abstractness vs Instability Graph and the zone of pain

To have more details about this graph you can refer to the Robert C.Martin article.

Here's the graph for Neo4j framework

AbstractnessVSInstability

The idea behind this graph is that the more a code element of a program is popular, the more it should be abstract. Or in other words, avoid depending too much directly on implementations, depend on abstractions instead. By popular code element I mean a project (but the idea works also for packages and types) that is massively used by other projects of the program. It is not a good idea to have concrete types very popular in your code base. This provokes some Zones of Pains in your program, where changing the implementations can potentially affect a large portion of the program. And implementations are known to evolve more often than abstractions.

The main sequence line (dotted) in the above diagram shows the how abstractness and instability should be balanced. A stable component would be positioned on the left. If you check the main sequence you can see that such a component should be very abstract to be near the desirable line - on the other hand, if its degree of abstraction is low, it is positioned in an area that is called the "zone of pain".

For example neo4j kernel has many classes depending on it, so it's positioned on the left and in this case it's preferable to be more abstract to leave the orange zone and goes to the green zone.

What's important is to avoid the zone of pain, if a jar is inside this zone, any changes to it will impact a lot of classes and it became hard to maintain or evolve this module.

More Stories By Lahlali Issam

Lahlali Issam Lead Developer at JavaDepend, a tool to manage and understand complex Java code. With JavaDepend, software quality can be measured using Code Metrics, visualized using Graphs and Treemaps, and queried using CQL language, a SQL like to query the code base.

@ThingsExpo Stories
SYS-CON Events announced today that EastBanc Technologies will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. EastBanc Technologies has been working at the frontier of technology since 1999. Today, the firm provides full-lifecycle software development delivering flexible technology solutions that seamlessly integrate with existing systems – whether on premise or cloud. EastBanc Technologies partners with p...
SYS-CON Events announced today that ContentMX, the marketing technology and services company with a singular mission to increase engagement and drive more conversations for enterprise, channel and SMB technology marketers, has been named “Sponsor & Exhibitor Lounge Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2016, at the Javits Center in New York City, New York. “CloudExpo is a great opportunity to start a conversation with new prospects, but what happens after the...
The IoTs 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, will demonstrate how to move beyond today's coding paradigm and share the must-have mindsets for removing complexity from the development proc...
SYS-CON Events announced today BZ Media LLC has been named “Media Sponsor” of SYS-CON's 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. BZ Media LLC is a high-tech media company that produces technical conferences and expositions, and publishes a magazine, newsletters and websites in the software development, SharePoint, mobile development and Commercial Drone markets.
SYS-CON Events announced today that Alert Logic, Inc., the leading provider of Security-as-a-Service solutions for the cloud, will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. Alert Logic, Inc., provides Security-as-a-Service for on-premises, cloud, and hybrid infrastructures, delivering deep security insight and continuous protection for customers at a lower cost than traditional security solutions. Ful...
SYS-CON Events announced today that MangoApps will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. MangoApps provides modern company intranets and team collaboration software, allowing workers to stay connected and productive from anywhere in the world and from any device. For more information, please visit https://www.mangoapps.com/.
WebRTC is bringing significant change to the communications landscape that will bridge the worlds of web and telephony, making the Internet the new standard for communications. Cloud9 took the road less traveled and used WebRTC to create a downloadable enterprise-grade communications platform that is changing the communication dynamic in the financial sector. In his session at @ThingsExpo, Leo Papadopoulos, CTO of Cloud9, will discuss the importance of WebRTC and how it enables companies to fo...
The IoT is changing the way enterprises conduct business. In his session at @ThingsExpo, Eric Hoffman, Vice President at EastBanc Technologies, discuss how businesses can gain an edge over competitors by empowering consumers to take control through IoT. We'll cite examples such as a Washington, D.C.-based sports club that leveraged IoT and the cloud to develop a comprehensive booking system. He'll also highlight how IoT can revitalize and restore outdated business models, making them profitable...
In his session at 18th Cloud Expo, Bruce Swann, Senior Product Marketing Manager at Adobe, will discuss how the Adobe Marketing Cloud can help marketers embrace opportunities for personalized, relevant and real-time customer engagement across offline (direct mail, point of sale, call center) and digital (email, website, SMS, mobile apps, social networks, connected objects). Bruce Swann has more than 15 years of experience working with digital marketing disciplines like web analytics, social med...
IoT generates lots of temporal data. But how do you unlock its value? How do you coordinate the diverse moving parts that must come together when developing your IoT product? What are the key challenges addressed by Data as a Service? How does cloud computing underlie and connect the notions of Digital and DevOps What is the impact of the API economy? What is the business imperative for Cognitive Computing? Get all these questions and hundreds more like them answered at the 18th Cloud Expo...
SYS-CON Events announced today the How to Create Angular 2 Clients for the Cloud Workshop, being held June 7, 2016, in conjunction with 18th Cloud Expo | @ThingsExpo, at the Javits Center in New York, NY. Angular 2 is a complete re-write of the popular framework AngularJS. Programming in Angular 2 is greatly simplified. Now it’s a component-based well-performing framework. The immersive one-day workshop led by Yakov Fain, a Java Champion and a co-founder of the IT consultancy Farata Systems and...
Customer experience has become a competitive differentiator for companies, and it’s imperative that brands seamlessly connect the customer journey across all platforms. With the continued explosion of IoT, join us for a look at how to build a winning digital foundation in the connected era – today and in the future. In his session at @ThingsExpo, Chris Nguyen, Group Product Marketing Manager at Adobe, will discuss how to successfully leverage mobile, rapidly deploy content, capture real-time d...
SYS-CON Events announced today that BMC Software has been named "Siver Sponsor" of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2015 at the Javits Center in New York, New York. BMC is a global leader in innovative software solutions that help businesses transform into digital enterprises for the ultimate competitive advantage. BMC Digital Enterprise Management is a set of innovative IT solutions designed to make digital business fast, seamless, and optimized from mainframe to mo...
What a difference a year makes. Organizations aren’t just talking about IoT possibilities, it is now baked into their core business strategy. With IoT, billions of devices generating data from different companies on different networks around the globe need to interact. From efficiency to better customer insights to completely new business models, IoT will turn traditional business models upside down. In the new customer-centric age, the key to success is delivering critical services and apps wit...
Join us at Cloud Expo | @ThingsExpo 2016 – June 7-9 at the Javits Center in New York City and November 1-3 at the Santa Clara Convention Center in Santa Clara, CA – and deliver your unique message in a way that is striking and unforgettable by taking advantage of SYS-CON's unmatched high-impact, result-driven event / media packages.
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, will provide an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life ...
SYS-CON Events announced today that MobiDev will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. MobiDev is a software company that develops and delivers turn-key mobile apps, websites, web services, and complex software systems for startups and enterprises. Since 2009 it has grown from a small group of passionate engineers and business managers to a full-scale mobile software company with over 200 develope...
SoftLayer operates a global cloud infrastructure platform built for Internet scale. With a global footprint of data centers and network points of presence, SoftLayer provides infrastructure as a service to leading-edge customers ranging from Web startups to global enterprises. SoftLayer's modular architecture, full-featured API, and sophisticated automation provide unparalleled performance and control. Its flexible unified platform seamlessly spans physical and virtual devices linked via a world...
Companies can harness IoT and predictive analytics to sustain business continuity; predict and manage site performance during emergencies; minimize expensive reactive maintenance; and forecast equipment and maintenance budgets and expenditures. Providing cost-effective, uninterrupted service is challenging, particularly for organizations with geographically dispersed operations.
SYS-CON Events announced today TechTarget has been named “Media Sponsor” of SYS-CON's 18th International Cloud Expo, which will take place on June 7–9, 2016, at the Javits Center in New York City, NY, and the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. TechTarget is the Web’s leading destination for serious technology buyers researching and making enterprise technology decisions. Its extensive global networ...