|By Michael Poulin||
|May 13, 2006 11:00 AM EDT||
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.
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:
3) independent from provider implementation and its resources
5) accessible programmatically
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.
Many banks and financial institutions are experimenting with containers in development environments, but when will they move into production? Containers are seen as the key to achieving the ultimate in information technology flexibility and agility. Containers work on both public and private clouds, and make it easy to build and deploy applications. The challenge for regulated industries is the cost and complexity of container security compliance. VM security compliance is already challenging, ...
May. 24, 2016 11:15 PM EDT Reads: 928
While there has been much ado about interoperability, there are still no real solutions, same as last year and the year before that. The large EHR vendors who continue to dominate the market still maintain that interoperability is all but solved, still can't connect EHRs across the continuum causing frustration by providers and a disservice to patients. The ONC pays lip service to the problem, but that is about it. It is time for the healthcare industry to consider alternatives like middleware w...
May. 24, 2016 09:45 PM EDT Reads: 1,457
With major technology companies and startups seriously embracing IoT strategies, now is the perfect time to attend @ThingsExpo 2016 in New York and Silicon Valley. Learn what is going on, contribute to the discussions, and ensure that your enterprise is as "IoT-Ready" as it can be! Internet of @ThingsExpo, taking place Nov 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 17th Cloud Expo and will feature technical sessions from a rock star conference faculty ...
May. 24, 2016 06:00 PM EDT Reads: 4,649
Our CTO, Anders Wallgren, recently sat down to take part in the “B2B Nation: IT” podcast — the series dedicated to serving the IT professional community with expert opinions and advice on the world of information technology. Listen to the great conversation, where Anders shares his thoughts on DevOps lessons from large enterprises, the growth of microservices and containers, and more.
May. 24, 2016 05:00 PM EDT Reads: 1,435
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, Containers, 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 opportunity. Submit y...
May. 24, 2016 05:00 PM EDT Reads: 1,842
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with the 19th International Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world and ThingsExpo New York Call for Papers is now open.
May. 24, 2016 04:00 PM EDT Reads: 1,681
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...
May. 24, 2016 02:00 PM EDT Reads: 3,847
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...
May. 24, 2016 01:45 PM EDT Reads: 2,058
@DevOpsSummit taking place June 7-9, 2016 at Javits Center, New York City, and Nov 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with the 18th International @CloudExpo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world.
May. 24, 2016 12:00 PM EDT Reads: 3,258
Just last week a senior Hybris consultant shared the story of a customer engagement on which he was working. This customer had problems, serious problems. We’re talking about response times far beyond the most liberal acceptable standard. They were unable to solve the issue in their eCommerce platform – specifically Hybris. Although the eCommerce project was delivered by a system integrator / implementation partner, the vendor still gets involved when things go really wrong. After all, the vendo...
May. 24, 2016 09:45 AM EDT Reads: 1,329
Small teams are more effective. The general agreement is that anything from 5 to 12 is the 'right' small. But of course small teams will also have 'small' throughput - relatively speaking. So if your demand is X and the throughput of a small team is X/10, you probably need 10 teams to meet that demand. But more teams also mean more effort to coordinate and align their efforts in the same direction. So, the challenge is how to harness the power of small teams and yet orchestrate multiples of them...
May. 24, 2016 09:15 AM EDT Reads: 1,804
SYS-CON Events announced today the Docker Meets Kubernetes – Intro into the Kubernetes World, being held June 9, 2016, in conjunction with 18th Cloud Expo | @ThingsExpo, at the Javits Center in New York, NY. Register for 'Docker Meets Kubernetes Workshop' Here! This workshop led by Sebastian Scheele, co-founder of Loodse, introduces participants to Kubernetes (container orchestration). Through a combination of instructor-led presentations, demonstrations, and hands-on labs, participants learn ...
May. 24, 2016 09:00 AM EDT Reads: 1,799
The initial debate is over: Any enterprise with a serious commitment to IT is migrating to the cloud. But things are not so simple. There is a complex mix of on-premises, colocated, and public-cloud deployments. In this power panel at 18th Cloud Expo, moderated by Conference Chair Roger Strukhoff, panelists will look at the present state of cloud from the C-level view, and how great companies and rock star executives can use cloud computing to meet their most ambitious and disruptive business ...
May. 24, 2016 09:00 AM EDT Reads: 1,987
The demand for organizations to expand their infrastructure to multiple IT environments like the cloud, on-premise, mobile, bring your own device (BYOD) and the Internet of Things (IoT) continues to grow. As this hybrid infrastructure increases, the challenge to monitor the security of these systems increases in volume and complexity. In his session at 18th Cloud Expo, Stephen Coty, Chief Security Evangelist at Alert Logic, will show how properly configured and managed security architecture can...
May. 24, 2016 09:00 AM EDT Reads: 1,963
Last week I had the pleasure of speaking on a panel at Sapphire Ventures Next-Gen Tech Stack Forum in San Francisco. Obviously, I was excited to join the discussion, but as a participant the event crystallized not only where the larger software development market is relative to microservices, container technologies (like Docker), continuous integration and deployment; but also provided insight into where DevOps is heading in the coming years.
May. 24, 2016 07:15 AM EDT Reads: 1,393
Admittedly, two years ago I was a bulk contributor to the DevOps noise with conversations rooted in the movement around culture, principles, and goals. And while all of these elements of DevOps environments are important, I’ve found that the biggest challenge now is a lack of understanding as to why DevOps is beneficial. It’s getting the wheels going, or just taking the next step. The best way to start on the road to change is to take a look at the companies that have already made great headway ...
May. 24, 2016 07:15 AM EDT Reads: 1,605
Agile teams report the lowest rate of measuring non-functional requirements. What does this mean for the evolution of quality in this era of Continuous Everything? To explore how the rise of SDLC acceleration trends such as Agile, DevOps, and Continuous Delivery are impacting software quality, Parasoft conducted a survey about measuring and monitoring non-functional requirements (NFRs). Here's a glimpse at what we discovered and what it means for the evolution of quality in this era of Continuo...
May. 24, 2016 06:45 AM EDT Reads: 1,406
You might already know them from theagileadmin.com, but let me introduce you to two of the leading minds in the Rugged DevOps movement: James Wickett and Ernest Mueller. Both James and Ernest are active leaders in the DevOps space, in addition to helping organize events such as DevOpsDays Austinand LASCON. Our conversation covered a lot of bases from the founding of Rugged DevOps to aligning organizational silos to lessons learned from W. Edwards Demings.
May. 24, 2016 06:45 AM EDT Reads: 1,320
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.
May. 24, 2016 06:00 AM EDT Reads: 3,389
When I talk about driving innovation with self-organizing teams, I emphasize that such self-organization includes expecting the participants to organize their own teams, give themselves their own goals, and determine for themselves how to measure their success. In contrast, the definition of skunkworks points out that members of such teams are “usually specially selected.” Good thing he added the word usually – because specially selecting such teams throws a wrench in the entire works, limiting...
May. 24, 2016 05:15 AM EDT Reads: 1,444