Welcome!

Microservices Expo Authors: Elizabeth White, Todd Matters, Pat Romanski, Kevin Jackson, ManageEngine IT Matters

Related Topics: Microservices Expo

Microservices Expo: Article

Does a Web Service Make a Service for SOA?

SOA Service & SOA SLA as drivers for renovating legacy applications for SOA

What could be easier than to take your application, wrap it with a Web Service, announce it or register it in the UDDI and get a SOA Service? Even better - take a data warehouse, cover a SQL executing code with a Web Service and expose it to SOA, isn't it simple? This article is for those architects and managers who like such "simplicity." If you believe that a Web Service itself doesn't convert an application into the SOA Service, you might read the article just out of curiosity.

A Service or Not a Service
Discussions about Service Oriented Architecture (SOA) initiated by people working with legacy applications and data storages like Data Warehouse (DW) have gotten a lot of press attention recently. While it's good for SOA's popularity the discussions typically declare a few SOA characteristics and say something like "We have so rich/important/business crucial data and, if we just expose it into a SOA, it will be great opportunity for us." An intention of exposing DW to a SOA sounds suspiciously like the five-year-old movement of exposing all applications to the Internet. Have we forgotten that mistake already? Have we understood the difference between Web applications and Web-enabled applications? Did anybody count the man-centuries spent in IT to convert and modify existing applications to make them really work in the Internet environment?

When I participate in such discussions, I usually ask one question: "To make some ground for DW working in SOA, please tell me what is a service in DW?" I am given two types of answers: either "none" or "We do a lot of data transformations and/or perform sophisticated data aggregation and produce business intelligence reports out of the DW." Well, data manipulation procedures performed in the DW might be considered as services, however, I have not found a definition of DW that would describe a service as a part of it. That is, DW wasn't designed for services.

Anyway, what's so special about a "service"? Why is wrapping access to a DW or an application with a Web Service not enough to obtain a service? What has to be done, if anything, to make such applications work in a SOA? Here I'll try to identify a process that could take place when one prepares a legacy application to support a Service for SOA.

Approach to a Definition of a "Service"
In different spheres of human activity, there may be many definitions of a service. My understanding of service behavior with regard to software components is an action/activity performed by the service provider for the service consumer in accordance to a contract between the provider and the consumer. While contracts may vary, the most flexible type unties/decouples/isolates a consumer from a provider. In the business, as we know, the consumer pays for the service and tends to consider a service provider a servant. This leads to two conclusions:

  • a consumer looks for a provider with the contract that meets the consumer's goals.
  • a consumer can agree with some of the constraints a contract puts on him if the contract still meets the goals and decouples the consumer from the provider's internal conditions.
The conclusions point to the difference between using a software component as a traditional application and using it as a service. In the former case, a consumer depends on the application specifics and, if something isn't suitable, the consumer has to adapt and wait for the application to be refined. In the latter case, a consumer deals with a service application only if the contract meets his needs and the application constraints are reasonable. For example, the constraints can provide some business values such as security, which adds business trust, or remote invocation, which can lead to service scalability and robustness.

Jumping ahead let me say that one SOA service can engage another SOA service doing this transparently to the consumer. If the second service provides the proper data based on an "update schedule", i.e., the data are obsolete for some period of time, the first service tends either to find a substitute service with the correct data for that period of time or switch to a totally different service, without any "schedule problems." In any case, the consumer shouldn't depend on that schedule. Otherwise, all service contracts have to reflect one service specifics, which leads to quite an insufficient architecture and, actually, couples services and consumer together. Described is not a SOA rule, it's a business rule and due to SOA agility principle, SOA promotes the same behavior.

Thus, the service contract can be used as a requirement when one transforms the application into a service. A well-known expression of a contract is a Service Level Agreement (SLA). There may be a single SLA for all consumers or the provider can maintain individual SLAs with every consumer. If we took a typical SLA used for DW, for instance, and a SLA used in SOA, we'd get the starting and ending points for the process we have to implement when exposing a DW to a SOA.

The process includes not only a new connectivity interface but changes in behavior dictated by the Service SLA. For immutable applications, the process assumes building a service façade layer to interact with other services and consumers.

Service Interface in SOA
SOA implies certain requirements in the service interface. In short, the interface has to be:
1)    stable
2)    self-describing
3)    independent from provider implementation and its resources
4)    registerable/searchable
5)    accessible programmatically
6)    versioned
7)    accessible under control (security)

As you see, there's nothing about the Web in the requirements. Indeed, any particular interface implementation is suitable if it meets the requirements. It may be, for example, CORBA IDL. As we know, many elements of Web Services specifications were derived from CORBA. So, why is a Web Service (WS) as an interface so attractive for SOA but still not enough?

Web Services technology defines the abstraction of service behavior via standard WS Description Language (WSDL). It also provides for the abstraction of data via XML and the metadata definition via XML Schema. WS technology offers a WS registry known as UDDI (Universal Description, Discovery, and Integration) and a set of standards to support security ( WS-Security and related standards), transaction (WS-TXM, WS-Coordination, WS-AtomicTransaction, and WS-BusinessActivity), aggregation and management (WS-BPEL and WS-CDL), and interoperability (WS-I Basic Profile).

Agreement between leading technology vendors on XML and most WS standards makes Web Services really the best candidate for a universal interface for SOA. Some specialists include SOAP (Simple Object Access Protocol) in the basis of SOA while others disagree with it and consider SOAP only one of several possible and convenient protocols for WS binding. SOAP alone simply doesn't provide enough abstraction for a service definition, that's why we need WSDL and we already know a few WS models that don't use SOAP binding.

What's not included in WSDL is the information considered by a consumer when he makes a business decision about the service. That is, you can automatically invoke a WS but you're not supposed to do so blindly, without estimating the inherited risk. It's simple: if you want to cook some French fries, you'd not use a pan without checking if it burns oil. The same relates to WS - the service may be accepted if you know its connectivity interface and its quality characteristics like performance, change control rules, error-handling scenarios, and so on. This information is usually described in the SLA. So a SLA can be treated as a container that includes business knowledge and service interface definition - both to meet the consumer's needs. A lot of legacy systems also work on the basis of SLA, however, those SLA are traditionally provider/application-centric.

Service Level Agreement for SOA Service
Currently, some efforts are made in the industry to define and formalize SLA for WS - these are specifications for Web Service Level Agreements (WSLA) and the Web Service Offerings Language (WSOL). The WSLA provides a structure of definitions of basic SLA elements. While it is a subject for separate article, we note the fact that the WSLA pairs SLA parameters with their metrics. That is, providing for SOA SLA means constant monitoring, analysis, and compliance reporting of actual runtime parameter values that aren't a part of most legacy application SLAs.

Though a SOA SLA isn't standardized yet, it's very important to understand what can be included in it. Table 1 gives an example of a SOA SLA. Some parameters are measurable (as represented in WSLA) and some of them aren't.

There are no mandatory or optional parameters in the SLA because they are all business- and context-specific. As mentioned already, neither Web Service/WSDL nor any other programming interface can address such SLAs. On the other hand, not all services require such detailed SLAs. Its can be periodically refined and extended when more objective information is gathered about the Service. The SLA demonstrates that participation in SOA requires both - the service interface and service behavior.

The only other thing I'd like to note is that it's better for maintenance and further enhancements if all services in your system have a unified SLA, especially when the number of Services is expected to grow over the time. Otherwise, managing the Services quickly gets out of hands. That is, the better you define the Service, the fewer problems you have at runtime and the more consumers you attract to use it.

Thinking in SOA
We can find tons of publications describing how to wrap a legacy application with a Web Service. Many serious works recommend the same solution - the most scalable and flexible way of wrapping is to create a thin layer on top of the legacy application. The "preserve-and-extend" approach has gained a reputation as being the most reliable and cost-effective model for dealing with business-critical legacy apps.

Some vendors propose developing connectors and gateways where the former run in a mainframe and latter outside the mainframe (screen-scraping). Both models act as proxies shielding actual applications and helping to provide SLA. Merrill Lynch, in particular, has created an integration platform using plug-ins with parsers, metadata assemblies, and drivers that runs on the mainframe and exposes legacy apps through Web Services via HTTP and MOM protocols. This platform is even called a Service Oriented Legacy Architecture. However, many experts suggest that transitioning a legacy application to a Service for a SOA isn't that straightforward: simple wrapping just "preserves" the application but doesn't make it a "first-class SOA citizen" without an "extension."

Let me give you two examples. The first one is about a traditional application in the financial industry; it may be considered a base line for the second example. Assume that the task is to calculate the credit risk of swap transactions (a special type of financial transactions). The transactions comprise the transaction data themselves, related financial streams, and cash flow data. These are dynamic elements that usually persist in an operational data store. Other related data about supply feeds and financial clients are static and usually persist in a reference data store.

The traditional application-centric approach of building a credit risk calculation component addresses the access interface(s)-access protocol(s) and defines data location, the data access mechanism (direct SQL, Stored Procedures, Views, security controls, etc.) and the data availability schedule. The team developing the application has to deal with its consumers (dictating application constraints) and constantly negotiate data status and updates with the database maintenance team. It leads to per-application specialized code that has to transform data to meet particular application needs. Any change in the data affects the application and all its consumers (via production re-deployment, at least). Such complex daily management task may be sufficiently executed if the team has enough resources and deals with only a few applications but this is a dream nowadays. A more realistic consequence is a shortage of resources and degraded quality, as well we know. And, there's no room left to support business growth.

A service-oriented approach defines the credit risk calculation engine and the metadata that the engine can work with. That is, the engine knows about different calculation formulas and intermediary data storages, if needed; it also knows how to deal with data if it meets metadata requirements. That's it. The consumer of the calculation service specifies what calculation to perform - for intra-day or end-of-day transactions. The input data is provided by another service, e.g., the Data Access Service (DAS), which also knows where to place calculated results. The calculation engine hasn't a clue where to get data from, what transactions to process, when to do the job; it only cares whether the DAS provides a SLA and acts appropriately if the SLA is violated. Now every development and support team can concentrate on its own business and provide related SLAs.


More Stories By Michael Poulin

Michael Poulin works as an enterprise-level solution architect in the financial industry in the UK. He is a Sun Certified Architect for Java Technology, certified TOGAF Practitioner, and Licensed ZapThink SOA Architect. Michael specializes in distributed computing, SOA, and application security.

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.


@MicroservicesExpo Stories
@DevOpsSummit at Cloud Expo taking place Oct 31 - Nov 2, 2017, at the Santa Clara Convention Center, Santa Clara, CA, is co-located with the 21st International 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 ...
For most organizations, the move to hybrid cloud is now a question of when, not if. Fully 82% of enterprises plan to have a hybrid cloud strategy this year, according to Infoholic Research. The worldwide hybrid cloud computing market is expected to grow about 34% annually over the next five years, reaching $241.13 billion by 2022. Companies are embracing hybrid cloud because of the many advantages it offers compared to relying on a single provider for all of their cloud needs. Hybrid offers bala...
You know you need the cloud, but you’re hesitant to simply dump everything at Amazon since you know that not all workloads are suitable for cloud. You know that you want the kind of ease of use and scalability that you get with public cloud, but your applications are architected in a way that makes the public cloud a non-starter. You’re looking at private cloud solutions based on hyperconverged infrastructure, but you’re concerned with the limits inherent in those technologies.
For organizations that have amassed large sums of software complexity, taking a microservices approach is the first step toward DevOps and continuous improvement / development. Integrating system-level analysis with microservices makes it easier to change and add functionality to applications at any time without the increase of risk. Before you start big transformation projects or a cloud migration, make sure these changes won’t take down your entire organization.
There's a lot to gain from cloud computing, but success requires a thoughtful and enterprise focused approach. Cloud computing decouples data and information from the infrastructure on which it lies. A process that is a LOT more involved than dragging some folders from your desktop to a shared drive. Cloud computing as a mission transformation activity, not a technological one. As an organization moves from local information hosting to the cloud, one of the most important challenges is addressi...
Managing mission-critical SAP systems and landscapes has never been easy. Add public cloud with its myriad of powerful cloud native services and this may not change any time soon. Public cloud offers exciting new possibilities for enterprise workloads. But to make use of these possibilities and capabilities, IT teams need to re-think everything they have done before. Otherwise, they will just end up using public cloud as a hosting platform for their workloads, aka known as “lift and shift.”
What's the role of an IT self-service portal when you get to continuous delivery and Infrastructure as Code? This general session showed how to create the continuous delivery culture and eight accelerators for leading the change. Don Demcsak is a DevOps and Cloud Native Modernization Principal for Dell EMC based out of New Jersey. He is a former, long time, Microsoft Most Valuable Professional, specializing in building and architecting Application Delivery Pipelines for hybrid legacy, and cloud ...
21st International Cloud Expo, taking place October 31 - November 2, 2017, 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. Me...
The reality of data ubiquity is here—data is buried in operational statistics, machine logs, stacks of overflowing tickets and customer details, among other things. How can any user get valuable information amid this rapid influx of data? Imagine a situation where your firm’s revenue takes a hit owing to an unexpected failure in some business process. It would be a nightmare for IT admins to sift through the interminable piles of data to deduce exactly why and where the problem occurred. To sav...
"Tintri focuses on the Ops side of the DevOps, which basically is pushing more and more of the accessibility of the infrastructure to the developers and trying to get behind the scenes," explained Dhiraj Sehgal of Tintri in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
SYS-CON Events announced today that CA Technologies has been named "Platinum Sponsor" of SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. CA Technologies helps customers succeed in a future where every business - from apparel to energy - is being rewritten by software. From planning to development to management to security, CA creates software that fuels transformation for companies in the applic...
Cloud Expo, Inc. has announced today that Andi Mann and Aruna Ravichandran have been named Co-Chairs of @DevOpsSummit at Cloud Expo Silicon Valley which will take place Oct. 31-Nov. 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. "DevOps is at the intersection of technology and business-optimizing tools, organizations and processes to bring measurable improvements in productivity and profitability," said Aruna Ravichandran, vice president, DevOps product and solutions marketing...
Both SaaS vendors and SaaS buyers are going “all-in” to hyperscale IaaS platforms such as AWS, which is disrupting the SaaS value proposition. Why should the enterprise SaaS consumer pay for the SaaS service if their data is resident in adjacent AWS S3 buckets? If both SaaS sellers and buyers are using the same cloud tools, automation and pay-per-transaction model offered by IaaS platforms, then why not host the “shrink-wrapped” software in the customers’ cloud? Further, serverless computing, cl...
In the decade following his article, cloud computing further cemented Carr’s perspective. Compute, storage, and network resources have become simple utilities, available at the proverbial turn of the faucet. The value they provide is immense, but the cloud playing field is amazingly level. Carr’s quote above presaged the cloud to a T. Today, however, we’re in the digital era. Mark Andreesen’s ‘software is eating the world’ prognostication is coming to pass, as enterprises realize they must be...
Hybrid IT is today’s reality, and while its implementation may seem daunting at times, more and more organizations are migrating to the cloud. In fact, according to SolarWinds 2017 IT Trends Index: Portrait of a Hybrid IT Organization 95 percent of organizations have migrated crucial applications to the cloud in the past year. As such, it’s in every IT professional’s best interest to know what to expect.
A common misconception about the cloud is that one size fits all. Companies expecting to run all of their operations using one cloud solution or service must realize that doing so is akin to forcing the totality of their business functionality into a straightjacket. Unlocking the full potential of the cloud means embracing the multi-cloud future where businesses use their own cloud, and/or clouds from different vendors, to support separate functions or product groups. There is no single cloud so...
Companies have always been concerned that traditional enterprise software is slow and complex to install, often disrupting critical and time-sensitive operations during roll-out. With the growing need to integrate new digital technologies into the enterprise to transform business processes, this concern has become even more pressing. A 2016 Panorama Consulting Solutions study revealed that enterprise resource planning (ERP) projects took an average of 21 months to install, with 57 percent of th...
In 2014, Amazon announced a new form of compute called Lambda. We didn't know it at the time, but this represented a fundamental shift in what we expect from cloud computing. Now, all of the major cloud computing vendors want to take part in this disruptive technology. In his session at 20th Cloud Expo, Doug Vanderweide, an instructor at Linux Academy, discussed why major players like AWS, Microsoft Azure, IBM Bluemix, and Google Cloud Platform are all trying to sidestep VMs and containers wit...
The taxi industry never saw Uber coming. Startups are a threat to incumbents like never before, and a major enabler for startups is that they are instantly “cloud ready.” If innovation moves at the pace of IT, then your company is in trouble. Why? Because your data center will not keep up with frenetic pace AWS, Microsoft and Google are rolling out new capabilities. In his session at 20th Cloud Expo, Don Browning, VP of Cloud Architecture at Turner, posited that disruption is inevitable for comp...
New competitors, disruptive technologies, and growing expectations are pushing every business to both adopt and deliver new digital services. This ‘Digital Transformation’ demands rapid delivery and continuous iteration of new competitive services via multiple channels, which in turn demands new service delivery techniques – including DevOps. In this power panel at @DevOpsSummit 20th Cloud Expo, moderated by DevOps Conference Co-Chair Andi Mann, panelists examined how DevOps helps to meet the de...