Welcome!

Java IoT Authors: Ruxit Blog, Sematext Blog, Elizabeth White, Craig Lowell, Greg O'Connor

Related Topics: Microservices Expo, Java IoT

Microservices Expo: Article

The Right End of REST

REST is all about distributed hypermedia applications. They’re the point of REST.

One of our Licensed ZapThink Architects, Michael Poulin, struggled with our recent ZapFlash, Where is the SOA in REST-Based SOA? In a forum post, Poulin asked:

If we have a UI that works with the middle- and back-end resources, do we care if … REST or Web Services are used behind the UI? If [the] UI all of a sudden becomes the orchestrator on its own (which contradicts the essence of Service with interfaces where one of [them is the] UI), how [may the] UI journey/workflow … be attributed to the communication channels - REST calls - running behind it? What constitute[s] “A REST application” … and how [does it differ] from non-REST application[s], especially from the architecture perspective? Where [is] the Architecture and where [is] the architecture Implementation?

Poulin is not alone in his confusion. The topic of REST is a minefield: it seems that most people don't understand it, even when they write authoritatively on the subject. And the true authoritative source, Dr. Roy Fielding, speaks in the precise yet obscure prose of an academic, often sowing as much confusion as he does clarity. And yet, the answers lie in Fielding's explanations, even though studying them feels a bit like sitting at the feet of the Buddha, hoping for enlightenment.

Unraveling REST
Let's begin with Wikipedia, a source Fielding bemoans as being a poor substitute for truth. Be that as it may, it's an expedient starting point. Wikipedia defines REST as "a style of software architecture for distributed hypermedia systems such as the World Wide Web." I always thought this definition was rather silly: after all, how many distributed hypermedia systems can you think of other than the Web? But in fact, this definition leads us to the answers to both of Poulin's core questions: first, what constitutes a REST application, and second, where is the architecture and where is its implementation?

Of course, Fielding's precise definition of REST differs from the Wikipedia simplification. According to Fielding, "the Representational State Transfer (REST) style is an abstraction of the architectural elements within a distributed hypermedia system." And therein lies the key to Poulin's second question: REST is an abstraction.

Of course, abstractions are nothing new-they are the basic tool of any architect, and a topic ZapThink has spoken about numerous times. But most people don't quite grok just how abstract REST is. For example, do you think that REST is HTTP-specific? No, it's not. It deals with abstracted hypertext protocols, of which HTTP is the most familiar. Does REST call for uniform interfaces consisting of GET, POST, PUT, and DELETE operations? No again. Those are examples of uniform interface operations, but REST itself doesn't specify them, other than an abstracted GET operation. And of course, resources are abstractions of server capabilities or entities, not the capabilities or entities themselves, while representations are abstractions of media type instances, not the instances themselves. Even the terms "client" and "server" are abstractions: a REST client may actually run on a physical server, and a REST server may serve as a client. In fact, there's nothing "client/server" about REST.

So when Wikipedia uses the phrase "a style of software architecture for distributed hypermedia systems such as the World Wide Web," it's pointing out that REST applies constraints to abstracted distributed hypermedia systems, of which the Web is only the most familiar example.

Confused yet? You're not alone, and that's the point. Architects look at the level of abstraction behind REST and wonder, "how can this mess be useful?" while developers look at it and think, "OK whatever, let's build a RESTful API and go from there." At that point, the architects take off their architect hats and dive into the technical details alongside the coders. The result? A lot of noise and confusion, ostensible RESTful APIs that are not really RESTful at all, and the mistaken belief that you can comply with some of the REST architectural constraints but not all of them, and still be doing some kind of REST.

And that brings us to Poulin's first question: what is a REST application anyway?

REST Applications: More than Bricks & Mortar
A REST application is a distributed hypermedia application, of course - something you apply a distributed hypermedia system to in order to accomplish some goal. Easy to say, but deceptively difficult to understand, until you realize that REST is all about distributed hypermedia applications. They're the point of REST. If you think you're "doing" REST without the goal of building a distributed hypermedia application, you're missing the point of REST entirely.

Unfortunately, most people who are trying to do REST, simply put, are missing the point of REST entirely!

It's as though we're trying to build a brick building, so we hire an architect who comes up with plans for a brick building. But we look at the plans and we don't really understand them, but we know we want to build with bricks, so we spend all our time figuring out the best way to mix mortar. Once we've come up with really good mortar, we convince ourselves we know how to build the building, even though we still don't understand the plan.

That's the state of REST today. People look at REST's four architectural constraints, and say, hmm, I don't understand the fourth one - Hypermedia as the Engine of Application State (HATEOAS). But I think I can figure out the bits about resources and representations. What they're failing to realize is the hypermedia bit is the point of what they're doing, just as actually building the building according to plan is the point of the mortar.

The mortar-first approach to REST has been institutionalized in the form of the Richardson Maturity Model, which suggests that HATEOAS is at the highest level of maturity, and it's perfectly fine to start at the lower levels and work your way up. In other words, it's fine to start construction once you have good mortar; you'll figure out the plan eventually. Clearly, that's no way to build a house!

The Right End of REST
What is it about HATEOAS that's so difficult? State engines? Computer Science 101, puhleeze. Hypermedia? Not really that confusing, either. After all, hypertext is just a document with links in it to other documents, and by generalizing hypertext to the term hypermedia, we're simply allowing for media other than HTML documents and the like. After all, a video or sound file could have a link in it, right? So, where's the confusion?

The confusion lies in the second letter A - application. As in distributed hypermedia application. The point of REST, remember? The architectural starting point for any implementation that REST constraints are appropriate for is the design of the hypermedia application that meets the given business requirements. If you look at the business requirements, and your expertise as an architect tells you that a distributed hypermedia application isn't the right thing to build, then don't use REST.

On the other hand, a distributed hypermedia application might be just the ticket. The next question you should ask is: how dynamic should this application be? In other words, what agility does the business require? Put the analysis that provides the answer to that question in your Agility Model. Then let the Agility Model - not the Richardson Maturity Model - guide your design.

RESTful Agility Levels
To illustrate the agility levels for distributed hypermedia applications that should frame your Agility Model, let's work through some concrete examples. As you go through these levels, compare them to the Richardson model.

Level 1: Static hypermedia application, consisting of a set of static Web pages containing nothing but HTML, interconnected by links. Not particularly agile. Is it REST? Yes, but in a very simplistic way. Does it meet your requirements? Probably not. (Level 1 is good enough for our ZapFlashes, however, in case you hadn't noticed.)

Level 2: Hypermedia application consisting of static Web pages that contain HTML and client-side JavaScript (no funky Ajax or the like). Pages link to each other, and the links may be dynamic, based upon client-side logic in the JavaScript.

Level 3: Hypermedia application consisting of dynamic Web pages built on the fly on the Web server, using php or Java Server Pages or whatever server scripting environment floats your boat. Pages link to each other, but the links may be dynamic, based upon server-side logic.

Level 4: Hypermedia application consisting of a set of dynamic representations that conform to a variety of media types (HTML documents, XML documents, images, video, you name it), where those representations have links to other representations, and furthermore, the links may be dynamic, based upon client-side or server-side logic or both, as appropriate.

Once you have determined the agility requirements for your application, now you may think about how best to implement its components - the hyperlinked representations. Answering that question finally leads you to a consideration of the resources that generate those representations. But you don't start with the resources, you start with the hypermedia application. You finish with the resources.

The ZapThink Take
The examples in the agility levels above are just that: examples. Particular implementation decisions that may be appropriate for a given situation. The architecture, however, is the overall, best practice-driven approach for beginning with the business challenge and working through the levels of abstraction to come up with a working implementation at the end. As an architectural style, REST is simply a set of constraints on the architecture: one way of doing things that makes it easier to solve certain problems. The architect must decide whether REST or any other style is appropriate for the problem at hand, but if you choose REST, then you must begin with the distributed hypermedia application you wish to build.

Hopefully I've answered Poulin's questions (I'm sure he'll let us know if I haven't). But there's still a part of his post left to address. If you read to the end, you'll see he wonders what happened to ZapThink. Well, Michael, we're a part of a larger company now, to be sure, but I'm still here, and I continue to do my best to push the envelope of architectural understanding. That's why we continue to update our Licensed ZapThink Architect course, which is now at version 9, and includes expanded content on REST-Based SOA, as you might expect. We hope to see you in a future class - and if you're in the Washington DC area, please come to our ZapForum networking event on October 12th and meet the "new" ZapThink. RSVP to [email protected] if you'd like to join us!

More Stories By Jason Bloomberg

Jason Bloomberg is the leading expert on architecting agility for the enterprise. As president of Intellyx, Mr. Bloomberg brings his years of thought leadership in the areas of Cloud Computing, Enterprise Architecture, and Service-Oriented Architecture to a global clientele of business executives, architects, software vendors, and Cloud service providers looking to achieve technology-enabled business agility across their organizations and for their customers. His latest book, The Agile Architecture Revolution (John Wiley & Sons, 2013), sets the stage for Mr. Bloomberg’s groundbreaking Agile Architecture vision.

Mr. Bloomberg is perhaps best known for his twelve years at ZapThink, where he created and delivered the Licensed ZapThink Architect (LZA) SOA course and associated credential, certifying over 1,700 professionals worldwide. He is one of the original Managing Partners of ZapThink LLC, the leading SOA advisory and analysis firm, which was acquired by Dovel Technologies in 2011. He now runs the successor to the LZA program, the Bloomberg Agile Architecture Course, around the world.

Mr. Bloomberg is a frequent conference speaker and prolific writer. He has published over 500 articles, spoken at over 300 conferences, Webinars, and other events, and has been quoted in the press over 1,400 times as the leading expert on agile approaches to architecture in the enterprise.

Mr. Bloomberg’s previous book, Service Orient or Be Doomed! How Service Orientation Will Change Your Business (John Wiley & Sons, 2006, coauthored with Ron Schmelzer), is recognized as the leading business book on Service Orientation. He also co-authored the books XML and Web Services Unleashed (SAMS Publishing, 2002), and Web Page Scripting Techniques (Hayden Books, 1996).

Prior to ZapThink, Mr. Bloomberg built a diverse background in eBusiness technology management and industry analysis, including serving as a senior analyst in IDC’s eBusiness Advisory group, as well as holding eBusiness management positions at USWeb/CKS (later marchFIRST) and WaveBend Solutions (now Hitachi Consulting).

@ThingsExpo Stories
Why do your mobile transformations need to happen today? Mobile is the strategy that enterprise transformation centers on to drive customer engagement. In his general session at @ThingsExpo, Roger Woods, Director, Mobile Product & Strategy – Adobe Marketing Cloud, covered key IoT and mobile trends that are forcing mobile transformation, key components of a solid mobile strategy and explored how brands are effectively driving mobile change throughout the enterprise.
With so much going on in this space you could be forgiven for thinking you were always working with yesterday’s technologies. So much change, so quickly. What do you do if you have to build a solution from the ground up that is expected to live in the field for at least 5-10 years? This is the challenge we faced when we looked to refresh our existing 10-year-old custom hardware stack to measure the fullness of trash cans and compactors.
The emerging Internet of Everything creates tremendous new opportunities for customer engagement and business model innovation. However, enterprises must overcome a number of critical challenges to bring these new solutions to market. In his session at @ThingsExpo, Michael Martin, CTO/CIO at nfrastructure, outlined these key challenges and recommended approaches for overcoming them to achieve speed and agility in the design, development and implementation of Internet of Everything solutions wi...
Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is expected in the amount of information being processed, managed, analyzed, and acted upon by enterprise IT. This amazing is not part of some distant future - it is happening today. One report shows a 650% increase in enterprise data by 2020. Other estimates are even higher....
Today we can collect lots and lots of performance data. We build beautiful dashboards and even have fancy query languages to access and transform the data. Still performance data is a secret language only a couple of people understand. The more business becomes digital the more stakeholders are interested in this data including how it relates to business. Some of these people have never used a monitoring tool before. They have a question on their mind like “How is my application doing” but no id...
Smart Cities are here to stay, but for their promise to be delivered, the data they produce must not be put in new siloes. In his session at @ThingsExpo, Mathias Herberts, Co-founder and CTO of Cityzen Data, will deep dive into best practices that will ensure a successful smart city journey.
DevOps at Cloud Expo, taking place Nov 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time to wait for long dev...
Identity is in everything and customers are looking to their providers to ensure the security of their identities, transactions and data. With the increased reliance on cloud-based services, service providers must build security and trust into their offerings, adding value to customers and improving the user experience. Making identity, security and privacy easy for customers provides a unique advantage over the competition.
SYS-CON Events announced today that 910Telecom will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Housed in the classic Denver Gas & Electric Building, 910 15th St., 910Telecom is a carrier-neutral telecom hotel located in the heart of Denver. Adjacent to CenturyLink, AT&T, and Denver Main, 910Telecom offers connectivity to all major carriers, Internet service providers, Internet backbones and ...
Almost two-thirds of companies either have or soon will have IoT as the backbone of their business in 2016. However, IoT is far more complex than most firms expected. How can you not get trapped in the pitfalls? In his session at @ThingsExpo, Tony Shan, a renowned visionary and thought leader, will introduce a holistic method of IoTification, which is the process of IoTifying the existing technology and business models to adopt and leverage IoT. He will drill down to the components in this fra...
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devices - comp...
Data is the fuel that drives the machine learning algorithmic engines and ultimately provides the business value. In his session at Cloud Expo, Ed Featherston, a director and senior enterprise architect at Collaborative Consulting, will discuss the key considerations around quality, volume, timeliness, and pedigree that must be dealt with in order to properly fuel that engine.
There is growing need for data-driven applications and the need for digital platforms to build these apps. In his session at 19th Cloud Expo, Muddu Sudhakar, VP and GM of Security & IoT at Splunk, will cover different PaaS solutions and Big Data platforms that are available to build applications. In addition, AI and machine learning are creating new requirements that developers need in the building of next-gen apps. The next-generation digital platforms have some of the past platform needs a...
19th Cloud Expo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, 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 strategy. Meanwhile, 94% of enterpri...
SYS-CON Events announced today Telecom Reseller 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. 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.
Pulzze Systems was happy to participate in such a premier event and thankful to be receiving the winning investment and global network support from G-Startup Worldwide. It is an exciting time for Pulzze to showcase the effectiveness of innovative technologies and enable them to make the world smarter and better. The reputable contest is held to identify promising startups around the globe that are assured to change the world through their innovative products and disruptive technologies. There w...
The 19th International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Digital Transformation, Microservices and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportuni...
I wanted to gather all of my Internet of Things (IOT) blogs into a single blog (that I could later use with my University of San Francisco (USF) Big Data “MBA” course). However as I started to pull these blogs together, I realized that my IOT discussion lacked a vision; it lacked an end point towards which an organization could drive their IOT envisioning, proof of value, app dev, data engineering and data science efforts. And I think that the IOT end point is really quite simple…
Personalization has long been the holy grail of marketing. Simply stated, communicate the most relevant offer to the right person and you will increase sales. To achieve this, you must understand the individual. Consequently, digital marketers developed many ways to gather and leverage customer information to deliver targeted experiences. In his session at @ThingsExpo, Lou Casal, Founder and Principal Consultant at Practicala, discussed how the Internet of Things (IoT) has accelerated our abil...
Is the ongoing quest for agility in the data center forcing you to evaluate how to be a part of infrastructure automation efforts? As organizations evolve toward bimodal IT operations, they are embracing new service delivery models and leveraging virtualization to increase infrastructure agility. Therefore, the network must evolve in parallel to become equally agile. Read this essential piece of Gartner research for recommendations on achieving greater agility.