Welcome!

Blog Feed Post

Cloud-Friendly BPM: The Power of Hypermedia-Oriented Architecture

post thumbnail

When ZapThink last wrote about Business Process Management (BPM) in the Cloud in March 2012, we challenged both vendors and BPM customers to rethink their approach to BPM software, eschewing a heavyweight middleware approach for the lightweight, hypermedia-oriented approach that Representational State Transfer (REST) encourages. And while we did generate some short-lived buzz, most of the response – or lack thereof – was little more than a resounding silence.

True, work on Cloud-friendly, REST-based BPM continues in certain dusty corners of academia, most notably in the research of Cesare Pautasso, a professor at the University of Lugano in Switzerland. But in spite of his notable contributions to Thomas Erl’s SOA with REST book, the enterprise software and Cloud marketplaces have largely either ignored or misunderstood his research as well as ZapThink’s on this topic.

While it’s amusing to theorize a vast vendor conspiracy, positing middleware dinosaurs actively working to distract their customer base from lighter weight, Cloud-friendly approaches, the reality is likely to be far more mundane. People just don’t get it. Or to be precise, our audience doesn’t get how all the pieces—BPM, REST, Cloud, and even a bit of SOA—fit together. To help resolve this confusion, let’s resort to an age-old technique: let’s draw some pictures.

Framing the Cloud-Friendly BPM Problem

Let’s start this discussion with an illustration of an admittedly simplistic business process involving one person and some back-end system, as shown in Figure 1 below.

Figure 1: Simple Two-Tier Process

Note that in the figure above, the user might tackle a few tasks, and then the server takes over, executing a few tasks on its own. While the server is busy doing its thing, the user might query the server as to the current status of the process.

So far so good, but we don’t want our server to serve only one user at a time. After all, the whole point of the client/server pattern is that it is many to one. As a result, we need to introduce the notion of a process instance. For the sake of simplicity let’s assume that we don’t have more than one person participating in a particular instance at the same time. But we might have multiple people each running their own instance of a process, for example, completing a purchase on a Web site, as shown in Figure 2 below.

 

Figure 2: Two Tier Process with Instance

In the figure above, the BPM engine running on the server spawns a process instance to deal with the interactions with the user. If multiple users initiate the same process, the server can instantiate as many process instances as necessary, and the engine keeps track of where every user is in their instance—in other words, the instance state.

How to keep track of all this state information in a scalable, robust manner is at the core of numerous distributed computing challenges. Today’s BPM engines generally run on Enterprise Service Buses (ESBs), which maintain state by spawning threads—short-lived, specialized object instances that run  in the execution environment of the ESB. But while threads are short-lived, process instances might take days or weeks to complete, and furthermore, threads are specific to the execution environment, making cross-ESB processes difficult to implement. For these reasons, we call state management the Achilles Heel of traditional, heavyweight (Web Services-based) SOA.

If such ESB-centric issues weren’t bad enough, the Cloud introduces a new wrinkle. Because we want to run our server in the Cloud, we don’t want to use it to maintain any state information, because we expect virtual machine (VM) instances to fail. In the Cloud, we provide automated recovery from failure rather than avoiding failure. However, if we store all the state information in the underlying persistence tier (not shown), then we limit our scalability, since every time anyone clicks a link, we must update a database somewhere.

What we need is a better way of dealing with state information that both allows our BPM engines to be Cloud friendly, and also frees us from the limitations of our ESBs. Or perhaps we must reinvent our ESBs to work in the Cloud. However you slice the problem, Hypermedia-Oriented Architecture (HOA) has the answer.

HOA to the Rescue

As ZapThink has discussed before, many people misconstrue REST as an API style that features a uniform interface, where in reality it’s a style of software architecture for building hypermedia systems. Why is the latter definition a better one? Because Roy Fielding, its creator, says so. That being said, work continues on the architectural context of REST, perhaps extending Fielding’s original thinking, as well as beyond the API style that most techies think of when they think about REST. We call this extension of the REST architectural style Hypermedia-Oriented Architecture, or HOA.

The central principle of HOA is the HATEOAS REST constraint: hypermedia is the engine of application state. In essence, HOA separates two different types of state information: application state and resource state. Application state corresponds to the user’s place in the runtime workflow consisting of hyperlinked representations, while resource state remains on the server, keeping track of persisted state information and state information that multiple users share.

On the one hand, HATEOAS requires hypermedia to manage all state information specific to individual clients, and on the other hand, delegates all other state information to the server. REST also specifies a set of verbs for querying an changing state information: GET for querying resource state without changing it,  and three verbs that change the resource state: POST for initializing a resource, PUT for updating a resource, and DELETE for deleting a resource (assuming we’re using HTTP as our transport protocol).

Note, therefore, that all verbs other than GET change the resource state, while all verbs, including GET, change the application state. Furthermore, all state information appears in the messages between client and server: the requests from client to resource, and the representations from resource to client. By extension, HATEOAS requires us to only use POST, PUT, or DELETE when—and only when—we must update resource state.

With this principle in mind, we have a real problem with the process in Figure 2. Note that the server is maintaining application state, which HOA forbids. But we can’t solve this problem simply by picking up the process instance from the server and sticking it in the client and expecting it to work properly, because sometimes we really do want to update the resource state. We somehow need to separate the process instance into two (or more) pieces so that hypermedia on the client can be the engine of application state while the BPM engine remains the engine of resource state.

Figure 3 below illustrates this principle. The client sends a POST to the server, which initializes a resource. In this case, that new resource sends a hypermedia representation to a stateless intermediary which caches the representation. This hypermedia representation is essentially an abstraction of a dynamic set of hyperlinked representations, for example, one or more php scripts that can generate a set of hyperlinked Web pages. Once the intermediary has the hypermedia representation, it returns the initial representation (for instance, a Web page) to the client.

Figure 3: HOA-Based Process with Stateless Intermediary

From that point on, as long as the client is navigating the application via hypermedia, changing only the application state as the user moves from one step in the process to the next, there is no need to change the resource state—and thus, no further POSTs, PUTs, or DELETEs are allowed. The client may perform a GET, because GETs change only the application state. The intermediary may be able to handle the GET on its own (if the necessary information is resident in the cache) or can turn around and perform a GET on an underlying resource, if necessary.

Furthermore, the application state may change without any interactions with the intermediary or the server by leveraging programmatic capabilities on the client. If the client is an arbitrary piece of software then this capability is trivial. But even if the client is a browser, it’s possible to change the state of an application without fetching anything from the server. In fact, there are many was to accomplish this feat.

Sometimes, of course, a hypermedia application, which we might also call a HOA process, must update resource state, for example, when it’s time to process the user’s credit card or change the number of widgets in inventory. Then—and only then—do we perform a PUT.

The most important characteristic of the process in Figure 3 is the fact that the intermediary is entirely stateless. If for some reason the VM that is hosting the hypermedia representation that is serving the client crashes, the Cloud environment must simply spawn a replacement and reload the same hypermedia representation as before. The client won’t lose its place because the hypermedia on the client are maintaining the application state. Similarly, we can horizontally scale the middle tier however and whenever we like. Instead of one VM hosting a particular hypermedia representation, we could have two or a hundred, and it doesn’t matter which one responds to a particular GET from the client.

Combining HOA Processes and Traditional BPM

The problem with the example in Figure 3, of course, is that every client’s process is separate from every other client’s process. However, most business processes in today’s organizations involve multiple parties—either multiple people or multiple enterprise applications or some combination.

On first glance, HOA doesn’t address such complex processes, since HATEOAS only deals with application state, not resource state. Fortunately, HOA works perfectly fine in this broader context as well, because it calls for a separation of application and resource state while providing for multiple ways to update resource state. After all, POST, PUT, and DELETE all update resource state, and any user can execute these verbs for a particular resource. Figure 4 below illustrates this more complex process.

Figure 4: HOA Process with Composite RESTful Service

In the figure above, a POST from a client instructs the BPM engine to instantiate a process instance on the server as in Figure 2. The first step in this process creates a hypermedia representation for the client to interact with as in Figure 3. Meanwhile, the resource state may change via any event, including a server-generated event or the action of a different user. If a user executes a PUT on the client to the hypermedia representation on the intermediary, then that representation turns around and PUTs to the appropriate underlying resource. Or perhaps the client PUTs to an underlying resource directly. Either way, the PUT goes to a hyperlink the client obtained from a previous representation at an earlier step in the process.

We might call the process running on the server a Composite RESTful Service, because the intermediary may abstract the entire server-based process via one or more RESTful URIs. A simple example of a Composite RESTful Service is a chat window application. Multiple users share the same chat session, so clearly the chat session state is part of the resource state.

There are a few essential points to keep in mind about the illustration in Figure 4. First, the intermediary remains stateless and therefore Cloud-friendly. We must maintain resource state in the persistence tier, but since we’ve offloaded the maintenance of application state to the client, we won’t be overburdening our database. We may also interact with our Composite RESTful Service via RESTful interactions, an essential benefit that Prof. Pautasso emphasizes in his research. And finally, not only is the middle tier horizontally scalable and elastic, so is the client tier—because every user brings their own client to the process.

The ZapThink Take

With the addition of an appropriate approach to building a RESTful Service abstraction, Figure 4 also serves as an illustration of how to implement RESTful SOA, what ZapThink refers to as “next generation” SOA in our Licensed ZapThink Architect (LZA) course as well as in my new book, The Agile Architecture Revolution. We therefore have a single, simple diagram bring together the worlds of SOA, BPM, Cloud, REST, and HOA.

The secret to getting all these architectural trends to work well together centers on how we deal with state information. We must first separate application state from resource state, and then subsequently take the conceptual leap to understanding that the best way to implement our business processes is by combining HOA processes with Composite RESTful Services. Once we make this leap, however, the pieces of this complicated puzzle finally fall into place.

Image credit: Bruce Guenter

Read the original blog entry...

More Stories By Jason Bloomberg

Jason Bloomberg is a leading IT industry analyst, Forbes contributor, keynote speaker, and globally recognized expert on multiple disruptive trends in enterprise technology and digital transformation. He is ranked #5 on Onalytica’s list of top Digital Transformation influencers for 2018 and #15 on Jax’s list of top DevOps influencers for 2017, the only person to appear on both lists.

As founder and president of Agile Digital Transformation analyst firm Intellyx, he advises, writes, and speaks on a diverse set of topics, including digital transformation, artificial intelligence, cloud computing, devops, big data/analytics, cybersecurity, blockchain/bitcoin/cryptocurrency, no-code/low-code platforms and tools, organizational transformation, internet of things, enterprise architecture, SD-WAN/SDX, mainframes, hybrid IT, and legacy transformation, among other topics.

Mr. Bloomberg’s articles in Forbes are often viewed by more than 100,000 readers. During his career, he has published over 1,200 articles (over 200 for Forbes alone), spoken at over 400 conferences and webinars, and he has been quoted in the press and blogosphere over 2,000 times.

Mr. Bloomberg is the author or coauthor of four books: The Agile Architecture Revolution (Wiley, 2013), Service Orient or Be Doomed! How Service Orientation Will Change Your Business (Wiley, 2006), XML and Web Services Unleashed (SAMS Publishing, 2002), and Web Page Scripting Techniques (Hayden Books, 1996). His next book, Agile Digital Transformation, is due within the next year.

At SOA-focused industry analyst firm ZapThink from 2001 to 2013, Mr. Bloomberg created and delivered the Licensed ZapThink Architect (LZA) Service-Oriented Architecture (SOA) course and associated credential, certifying over 1,700 professionals worldwide. He is one of the original Managing Partners of ZapThink LLC, which was acquired by Dovel Technologies in 2011.

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), and several software and web development positions.

Latest Stories
Without lifecycle traceability and visibility across the tool chain, stakeholders from Planning-to-Ops have limited insight and answers to who, what, when, why and how across the DevOps lifecycle. This impacts the ability to deliver high quality software at the needed velocity to drive positive business outcomes. In his general session at @DevOpsSummit at 19th Cloud Expo, Eric Robertson, General Manager at CollabNet, will discuss how customers are able to achieve a level of transparency that e...
It is ironic, but perhaps not unexpected, that many organizations who want the benefits of using an Agile approach to deliver software use a waterfall approach to adopting Agile practices: they form plans, they set milestones, and they measure progress by how many teams they have engaged. Old habits die hard, but like most waterfall software projects, most waterfall-style Agile adoption efforts fail to produce the results desired. The problem is that to get the results they want, they have to ch...
Organizations planning enterprise data center consolidation and modernization projects are faced with a challenging, costly reality. Requirements to deploy modern, cloud-native applications simultaneously with traditional client/server applications are almost impossible to achieve with hardware-centric enterprise infrastructure. Compute and network infrastructure are fast moving down a software-defined path, but storage has been a laggard. Until now.
"Venafi has a platform that allows you to manage, centralize and automate the complete life cycle of keys and certificates within the organization," explained Gina Osmond, Sr. Field Marketing Manager at Venafi, in this SYS-CON.tv interview at DevOps at 19th Cloud Expo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
"We're focused on how to get some of the attributes that you would expect from an Amazon, Azure, Google, and doing that on-prem. We believe today that you can actually get those types of things done with certain architectures available in the market today," explained Steve Conner, VP of Sales at Cloudistics, 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.
For far too long technology teams have lived in siloes. Not only physical siloes, but cultural siloes pushed by competing objectives. This includes informational siloes where business users require one set of data and tech teams require different data. DevOps intends to bridge these gaps to make tech driven operations more aligned and efficient.
Without a clear strategy for cost control and an architecture designed with cloud services in mind, costs and operational performance can quickly get out of control. To avoid multiple architectural redesigns requires extensive thought and planning. Boundary (now part of BMC) launched a new public-facing multi-tenant high resolution monitoring service on Amazon AWS two years ago, facing challenges and learning best practices in the early days of the new service.
DXWorldEXPO LLC announced today that the upcoming DXWorldEXPO | CloudEXPO New York event will feature 10 companies from Poland to participate at the "Poland Digital Transformation Pavilion" on November 12-13, 2018.
Digital Transformation is much more than a buzzword. The radical shift to digital mechanisms for almost every process is evident across all industries and verticals. This is often especially true in financial services, where the legacy environment is many times unable to keep up with the rapidly shifting demands of the consumer. The constant pressure to provide complete, omnichannel delivery of customer-facing solutions to meet both regulatory and customer demands is putting enormous pressure on...
The best way to leverage your CloudEXPO | DXWorldEXPO presence as a sponsor and exhibitor is to plan your news announcements around our events. The press covering CloudEXPO | DXWorldEXPO will have access to these releases and will amplify your news announcements. More than two dozen Cloud companies either set deals at our shows or have announced their mergers and acquisitions at CloudEXPO. Product announcements during our show provide your company with the most reach through our targeted audienc...
With 10 simultaneous tracks, keynotes, general sessions and targeted breakout classes, @CloudEXPO and DXWorldEXPO are two of the most important technology events of the year. Since its launch over eight years ago, @CloudEXPO and DXWorldEXPO have presented a rock star faculty as well as showcased hundreds of sponsors and exhibitors!
In an era of historic innovation fueled by unprecedented access to data and technology, the low cost and risk of entering new markets has leveled the playing field for business. Today, any ambitious innovator can easily introduce a new application or product that can reinvent business models and transform the client experience. In their Day 2 Keynote at 19th Cloud Expo, Mercer Rowe, IBM Vice President of Strategic Alliances, and Raejeanne Skillern, Intel Vice President of Data Center Group and ...
More and more brands have jumped on the IoT bandwagon. We have an excess of wearables – activity trackers, smartwatches, smart glasses and sneakers, and more that track seemingly endless datapoints. However, most consumers have no idea what “IoT” means. Creating more wearables that track data shouldn't be the aim of brands; delivering meaningful, tangible relevance to their users should be. We're in a period in which the IoT pendulum is still swinging. Initially, it swung toward "smart for smart...
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...
DXWorldEXPO LLC announced today that All in Mobile, a mobile app development company from Poland, will exhibit at the 22nd International CloudEXPO | DXWorldEXPO. All In Mobile is a mobile app development company from Poland. Since 2014, they maintain passion for developing mobile applications for enterprises and startups worldwide.