Welcome!

Weblogic Authors: Yeshim Deniz, Elizabeth White, Michael Meiner, Michael Bushong, Avi Rosenthal

Related Topics: Microservices Expo

Microservices Expo: News Item

Where Is the SOA in REST-Based SOA?

We must pare down the essentials of both REST and SOA to understand the true nature of the combined approach.

Over the years, updating our Licensed ZapThink Architect (LZA) course has given us ample time to explore advances in SOA and Cloud Computing. Now that we’re working on version 9 of the course, we’re taking a closer look at REST-based SOA. Of course, ZapThink has discussed REST for several years now, but recently we’ve seen some fascinating REST-based SOA case studies, both at startups as well as within the US Federal Government.

Nevertheless, while many architects believe that as an architectural style, REST is simpler and more straightforward that Web Services-based SOA, our research is turning up continued confusion over the principles of REST and how best to implement them. Everybody seems to get the basics—operate on resources at URIs with the four HTTP-centric operations GET, POST, PUT, and DELETE—but most people seem to miss the subtleties. Combine that confusion with the fact that you can do REST without SOA, the specifics of REST-based SOA are even more elusive, as we must pare down the essentials of both REST and SOA to understand the true nature of the combined approach. How, therefore, should we handle Service abstractions, contracts, and compositions – arguably, the essence of SOA – in a REST-based SOA world?

Where is the Service Abstraction?
At the center of the SOA approach is the notion of a Service abstraction. REST resources are abstractions as well, but resources are abstractions of capabilities or entities on the server, which is not quite the same thing as a Service abstraction. In SOA, the Service abstraction supports Business Services, which represent flexible, business-centric capabilities. A Business Service may abstract multiple Service interfaces, where routing and transformation operations on intermediaries present a loosely coupled façade.

Most RESTafarians, however, don’t think at this level. They are thinking of clients (e.g. browsers) accessing resources at URIs which return representations. A representation is an HTML page, an XML file, a video, etc. The business context is lost in a sea of URI formats and Internet media types.

What RESTafarians often overlook is that the intermediary pattern is actually one of the core architectural constraints of REST. URIs need not point directly to resources; it is perfectly OK for an intermediary to resolve the URI into a physical endpoint. After all, that’s what DNS servers do!

From the SOA perspective, we can rely upon the intermediary to execute routing rules and transformations as necessary to support the business abstraction. Furthermore, we can establish and enforce the policy (as a part of our SOA governance framework) that the only allowed way to access resources is via endpoints on an intermediary. From the REST perspective, think DNS server on steroids: instead of simply resolving URLs to IP addresses, resolve any formal URI structure to physical resource endpoints by following a rich set of transformation and routing metadata.

Where is the Contract?
At the technical level, a Service is a contracted interface or an abstraction of contracted interfaces. Web Services have contracts that comply with WSDL, but there’s no equivalent of WSDL for REST resources. True, resources have uniform interfaces that the four HTTP operations define, but simply knowing you can GET a resource or POST to a resource doesn’t tell you anything about what that resource is supposed to do. Accessing a resource does give you a representation of that resource, however. Representations can comply with standard Internet media types (formerly known as MIME types), but even the media type specification is insufficient to qualify as a contract.

Sun Microsystems tried to promote the Web Application Description Language (WADL) as a RESTafarian alternative to WSDL, but work on WADL has largely petered out now that Sun is part of Oracle. The point to WADL was more to stub out REST resources in Java than to provide an implementation-neutral contract language in any case.

Where, then, is the contract? Let’s look at a simple REST example: the simplest, of course, being the Web itself. Let’s say you are filling in a form on a Web page and then hit submit. Where is the contract?

The form method is POST, and the POST data are the information that you filled into the form. The resource is identified by the form action URL. So far so good. Have you found the contract yet?

In this example, the contract is the Web form itself. The form specifies and constrains the POST data you may input, and specifies the form action, which is a hyperlink to the next resource. You browsed to the page with the Web form by following an earlier link or loading a URL for a resource that returned that Web page as a representation of that resource.

Remember, a REST application is a set of resources that return representations that link to other resources – in other words, hypermedia. One resource returns one or more representations (Web pages, XML files, etc.) that contain links to other resources, and it is those hyperlinks (and their associated metadata) that specify the application behavior.

While a Web page with a form is the simplest and most common example of how to contract POST data, we can generalize that form however we like, depending on what type of client we want to support. For machine-to-machine interactions, for example (that is, when the client is not simply a browser), the first resource may return an XML representation that provides a contracted interface to the client for POSTing to the linked resource. How your resource builds that representation is up to you.

In Web Services-based SOA we store the contract metadata in a centralized registry/repository. In REST-based SOA each resource is responsible for returning contract metadata either for itself or for any resource it hyperlinks to. As a result, we may not able to obtain contracts for resources we’re not (yet) able to access, but on the other hand, we can code our resources to dynamically generate contracts if we wish. In REST-based SOA, therefore, contract changes can be automated, where in Web Services-based SOA, contract change is a complex, manual process that requires rigorous governance.

Where is the Composition?
The third core characteristic of SOA we look for is the ability to compose Services into applications. Such compositions might be orchestrations, when they have a pre-defined flow, or choreographies, when the order of steps in the composition is not determined ahead of time.

A REST application, of course, is an example of a composition of resources. From the SOA perspective, furthermore, a REST application is a workflow – that is, a composition with human steps. We can also consider such compositions to be choreographies, because the order of steps depends upon which links the user clicks. Users may click links in a different order every time they work their way through the application.

The question still remains: how do we create automated orchestrations in the REST world? The answer is simpler than it looks. In REST, everything can be a resource. Therefore, orchestrations can be resources as well. An orchestration resource might return a BPEL representation or a BPMN representation or perhaps a simplified representation of an orchestration that doesn’t have the baggage of either BPEL or BPMN. If anything, establishing a pre-defined orchestration is simpler than a hypermedia composition, because the orchestration logic is static, while with a hypermedia composition, the underlying resource logic may change the composition logic on the fly. Just because we don’t have to fix our application state transitions ahead of time doesn’t mean we’re not allowed to.

The ZapThink Take
Over the more than ten years ZapThink has been writing about SOA, we’ve fought the battle to explain what SOA really was, fighting the deluge of misinformation from profit-seeking vendors and ill-informed industry analysts. Fortunately, this time vendors aren’t trying to coopt REST to sell software the way they did SOA, to be sure, but the fact still remains that there is extensive confusion and misinformation about REST, just as there still is for SOA.

Mix the two together, therefore, and you’re just asking for trouble. But the effort is worth the trouble, for one simple fact: done right, REST-based SOA actually works. It paves a path to the agile architecture that we’ve been seeking since we first dipped our toe into the ocean of distributed computing. Of course, there’s a catch: the “done right” bit. The devil is in the details.

ZapThink will be providing far more detail on this topic over the next year, in our ZapFlash newsletters, in the next version of our LZA course, and in our Podcasts and at our events. Our new REST-based SOA module in the LZA course in particular breaks new ground and lays the groundwork for simpler, more successful approaches to SOA. Hope to see you at one of our events or classes soon!

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
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...
"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.
"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...
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.
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...
"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.
"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.
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...
"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...
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.
"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.
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 ...
It is of utmost importance for the future success of WebRTC to ensure that interoperability is operational between web browsers and any WebRTC-compliant client. To be guaranteed as operational and effective, interoperability must be tested extensively by establishing WebRTC data and media connections between different web browsers running on different devices and operating systems. In his session at WebRTC Summit at @ThingsExpo, Dr. Alex Gouaillard, CEO and Founder of CoSMo Software, presented ...
WebRTC is great technology to build your own communication tools. It will be even more exciting experience it with advanced devices, such as a 360 Camera, 360 microphone, and a depth sensor camera. In his session at @ThingsExpo, Masashi Ganeko, a manager at INFOCOM Corporation, introduced two experimental projects from his team and what they learned from them. "Shotoku Tamago" uses the robot audition software HARK to track speakers in 360 video of a remote party. "Virtual Teleport" uses a multip...
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, whic...
SYS-CON Events announced today that Evatronix will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Evatronix SA offers comprehensive solutions in the design and implementation of electronic systems, in CAD / CAM deployment, and also is a designer and manufacturer of advanced 3D scanners for professional applications.
Leading companies, from the Global Fortune 500 to the smallest companies, are adopting hybrid cloud as the path to business advantage. Hybrid cloud depends on cloud services and on-premises infrastructure working in unison. Successful implementations require new levels of data mobility, enabled by an automated and seamless flow across on-premises and cloud resources. In his general session at 21st Cloud Expo, Greg Tevis, an IBM Storage Software Technical Strategist and Customer Solution Architec...
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 ...
An increasing number of companies are creating products that combine data with analytical capabilities. Running interactive queries on Big Data requires complex architectures to store and query data effectively, typically involving data streams, an choosing efficient file format/database and multiple independent systems that are tied together through custom-engineered pipelines. In his session at @BigDataExpo at @ThingsExpo, Tomer Levi, a senior software engineer at Intel’s Advanced Analytics gr...
When talking IoT we often focus on the devices, the sensors, the hardware itself. The new smart appliances, the new smart or self-driving cars (which are amalgamations of many ‘things’). When we are looking at the world of IoT, we should take a step back, look at the big picture. What value are these devices providing? IoT is not about the devices, it’s about the data consumed and generated. The devices are tools, mechanisms, conduits. In his session at Internet of Things at Cloud Expo | DXWor...