Welcome!

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

Related Topics: Microservices Expo

Microservices Expo: Article

Future-Proofing Solutions with Coarse-Grained Service Oriented Architecture

Future-Proofing Solutions with Coarse-Grained Service Oriented Architecture

Web services and service-oriented architectures are transforming application construction. The ubiquity of Web services support by all leading platform venders brings the promise of a flexible application environment with simplified interface techniques, location transparency, and platform-neutral interoperability. This dynamic infrastructure brings about a new implementation approach, the service-oriented architecture.

However, to date most Web services projects have really only created simplified communication mechanisms for the invocation of those same old complicated legacy interfaces that we have always had. To truly realize the creation of service-based components, a new design approach is needed, one that produces simple, straightforward coarse-grained service interfaces that conceal the ugliness of the legacy low-level interfaces. Designing coarse-grained interfaces is not as easy as it sounds. This article discusses how to recognize good coarse-grain interfaces and how to design coarse-grain interfaces for maximum flexibility and longevity.

When you use a service, be it a bank, a restaurant, or a store, you expect to easily interact with that service. How would the restaurant-goers experience be if there was a different process for ordering each part of the meal, or when withdrawing cash at an ATM, there were a hundred different menu options. Service interfaces are expected to be simple and intuitive. This is what makes a service successful. New services should be easily discoverable and the consumption of those interfaces undemanding. ATM machines are ubiquitous because everyone knows or can easily learn how to use one.

The proper design of a service should take an "outside in" approach to constructing the interface by focusing on the client application's perspective and how the component plays within the larger business process context. Sadly, many interface designs take an "inside out" approach by basing the interface design on the dirty details of the existing implementation rather than the specific requirements for client utilization. The interface should be on a "need-to-know" basis, only exposing interface details that are meaningful to semantics of the larger interaction with client applications.

 

Ongoing software maintenance is a constant burden for business applications. Today's development is tomorrow's legacy. Loosely coupled service-oriented architectures create an opportunity to reverse this escalating legacy cycle. Proper design of the interfaces can minimize changes as requirements evolution occurs, making these services future-proof.

The Problem
Most poor interfaces are the result of allowing a convoluted implementation to bleed through into the interface. Even a good implementation that is transparently presented as a Web service becomes a thorny service interface. A component often contains dozens of classes and hundreds of methods. Exposing this detail as a service is analogous to an ATM machine with hundreds of menu options. Complicated interface designs impose unnecessary responsibilities on the client application, for example:

  • They result in excessive chattiness over the Web services interface.
  • They overburden the client application with the maintenance of the service component's context.
  • They force the client application to become co-dependent with the service component requiring dual development for the life of the solution.

    This poor interface design will sign a death sentence for the component and the service-oriented implementation by tightly coupling the client application with the component, requiring future maintenance of intricate interaction semantics and proprietary interaction context.

    Interaction Semantics
    Part of the problem is that the mechanism for interacting with a component is different from - and often in some very bizarre ways - any other component. The client application needs costly custom implementation for invocation of the interface of each component. This is reminiscent of Indiana Jones navigating through hidden passageways to find the lost treasure with secret incantations required for entrance to each secret chamber. In their book BPM: the Third Wave (Meghan-Kiffer Press, 2001), Howard Smith and Peter Fingar expanded this thought: "Imagine a world where people speak a language that brilliantly describes the molecular structure of a large object but can't tell you what that object is - or that it's about to fall on you." The reason for failure of component interoperability from this perspective is self-evident.

    We remember a recent engagement for the integration of physician practice applications with a hospital IS system that had outlandish interface semantics. Ignoring reasonable practices and embracing the quirks of their implementation, the system required that the patient's first and middle name fields be left blank and the last name field contain the patient's full name. This is just one of the many urban legends of strange system interfaces that litter the IT landscape.

    Burden of Context
    Another problem of low-level proprietary interfaces is that the client application is pulled into the internal context of the called component. With multiple method invocations for any coarse-grained operation, there is a need to maintain implementation context in the client application in order to provide that context on subsequent method calls. One example of a system from a recent project would require special codes indicating proprietary state and numeric status codes (e.g., code="F", Status="989"), which had no relevance to the client application, to drive the invocation of each operation. Implementation-specific state information was forced onto the client application by the component. The delineation between the relevant context of the interaction (that which is meaningful to both the client and the component) and irrelevant context (the exclusive state information of the component) is often not considered during interface design.

    Context in terms of resource references, processing state, and method parameter values are unnecessarily forced into the interface. As the interface grows so does the interaction context. The client application has its own context to maintain and does not need to be burdened with the component's implementation context.

    Example: Customer Management System Interface
    To illustrate the difficulty presented by exposed low-level interfaces, look at a customer-service application that has a component for customer. With objects for atomic elements of the customer information results in the client application, implementation might look like the following:

    customer = CustomerManage.findCustomer("123456789");
    customerID = customer.getCustomerID();
    addressVector = addressList.findAddresses(customerID)
    homeAddress = addressVector.findAddress("Home")
    homePhone = homeAddress.getPhone();
    shipTo = addressVector.findAddress("Ship To");
    shipToZip = shipTo.getZip();

    This demonstrates how the client application is pulled into an unnecessary interaction context that it has no concern with.

    Designing for Serviceability
    Creating a coarse-grained interface that truly embodies a service must be a conscious part of the interface design process. Serviceability comes from an interface that is easy to exploit, straightforward, and has a life span beyond the first version. To discuss these characteristics of coarse-grained service design, we'll borrow the ACID acronym from the transactional processing domain:

  • Atomic: Any one business operation can be completed through one service interface. The coarse-grained interface is close to a 1:1 ratio of business operations to service interfaces. In document-oriented Web service interfaces the interface is simplified to the semantics of document exchange.
  • Consistent: There is a consistent behavior to the interface within a domain that makes new services in that domain easily recognizable and understood. Consistency extends beyond the interfaces of one component to a common interface format for all components within a domain. Locating services instances, establishing context, retrieving data, performing updates, and executing business operations all have consistent interaction. One of the best ways to do this is with a FCRUD semantic where service resource objects are operated with straightforward semantics of the Find resource, Create resource, Retrieve resource information, Update resource information, and Delete resource. Consistent interaction semantics empower the client application developer to easily utilize any of the service components once he or she has experience developing an interface to one.
  • Isolated: Any one interface can be invoked independent of other service interfaces. Component implementation context and detailed invocation sequencing are not forced onto the client application. Loose coupling exists rather than tight semantic coupling. Predecessor and successor invocation requirements are not part of the interaction beyond the degree that they are part of the shared process between the client and the component. Isolation of interface design enables the client application to invoke any service interface with a minimum of preconditional interaction, perhaps only a Find resource call.
  • Durable: This interface has been designed with a vision of the future and has longevity built into it. The interface envisions the broad range of usage scenarios and future implementation enhancements and has been designed with an eye towards ease of migration. A durable interface is future-proof, not that the interface will never change, but it has the capability to easily incorporate future enhancements. Document-centric Web service interfaces and other loosely coupled interface techniques minimize the impact of extensions to the interface.

    How do you design ACID characteristics into your service component interfaces to best ensure successful exploitation in a service-oriented architecture? The best way is by proper modeling of the component interface. Modeling often looks inward. It is easy for programmers to immediately concern themselves with the implementation while the interface and its usage become a background activity. Taking an "outside in" approach to the modeling ensures that consideration is properly given to the continuum of utilization.

    Correct modeling takes a top-down approach beginning with the business processes and requirements for the solutions that the component service envisions being exploited in. Correct modeling should begin at the domain level by identifying the business context of the component usage and what business processes would exploit the component. For each business process, identify the use cases or scenarios that demonstrate the various ways the process could be executed. These process use cases lead to specific use cases of component interaction.

    This top-down approach ensures that the context of the process is firmly established before design looks inward at the interface and implementation of the component. Although it may seem like overkill, establishing use cases at the domain level will ensure that correct specification of the service is created and future-proofs that component by anticipating all possible usage scenarios.

    Proper Service Interface - Customer Management System Interface
    Returning to our customer component example, you can see how a proper coarse-grain interface results in a simplified client implementation without the burden of component context or proprietary interaction semantics:

    customerdocument =
    CustomerManageService.getCustomerDocument("123456789");
    homePhone = customerdocument.getHomePhone();
    shipToZip = customerdocument.getShiptToZip();

    This document-centric interface requires only one service invocation, which returns a document containing all the necessary information the client application requires without the burden of implementation details.

    Creating Coarse Grain Implementations
    Typically a Web services project focuses primarily on migrating existing application functionality to a Web services interface. The preexisting application can be anything from legacy systems to J2EE Enterprise JavaBeans (EJBs). How do you map this to a coarse-grain service interface? Very seldom will traditional low-level interfaces naturally map to a proper coarse-grained structure. An abstraction layer is required to hide the details of the implementation from the user behind a facade. This abstraction layer encapsulates:

  • Multiple low-level interfaces that comprise the business operation
  • Multiple data sources that need to be aggregated for the service
  • Legacy system interaction
  • The sequencing of low-level calls
  • Maintaining context for the low-level implementations
  • Transactional coordination of updates to multiple low-level interfaces

    The abstraction layer can be constructed using either of two approaches:
    1.   Build to integrate: Using application development techniques, a facade or mediator is implemented to provide the interface that aggregates the lower-level interfaces. Coarse-grained components are created that broker the interactions with multiple classes. Traditional application development tools and techniques can be employed for development of this facade. Component development environments like J2EE or Microsoft's .NET provide application environments to host both the facade component and the implementation.
    2.   Enterprise application integration (EAI)/ Business process integration (BPI): EAI tools exist for the purpose of integrating applications together. They provide rich tools and functionality for rapidly integrating all types of applications, including legacy, Web, and packaged software applications. BPI tools extend this capability to provide choreography of the business process and application flow outside the application. Web services-based integration is now a component of almost all EAI/BPI tools. This means that these tools can expose their integration flows through coarse-grain Web services interfaces.

     

    Which is a better choice depends on a number of factors. Some things to consider are if the implementations are of similar technologies, what interfaces these lower-level interfaces currently support, and whether legacy systems are part of the equation. Often it comes down to whether the primary focus of the project is application development or business integration.

    Conclusion
    The success of service-oriented architectures depends on a rich universe of available services that are easily located, understood, and utilized by a diverse community of users. These interfaces must have a life span beyond the first implementation, which can only be achieved by proper design of coarse-grained interfaces that are truly coarse-grain in nature and not just a weak veneer on top of an existing tortuously complicated interfaces. By taking an "outside-in" approach to modeling the service component interface, it is possible to identify the full spectrum of usage of the component.

    As you design services, remember the ACID acronym and ask yourself if the interface models a full atomic business operation; is there consistency to the interface across the family of components; can any one interface be invoked in reasonable independence from other interfaces; and has the interface been designed with a view towards future usage scenarios. This perspective will lead to components that can truly become ubiquitous services in the Web services world.

  • More Stories By John Medicke

    John Medicke is the chief architect of the On Demand Solution Center
    in Research Triangle Park, NC. He has designed solutions for various
    industries including financial services, retail, healthcare, industrial,
    and government. John has worked extensively on the exploitation of
    business integration, business process management, and business
    intelligence within an integrated solution context. He is author of the
    book Integrated Solutions with DB2, as well as several articles.

    Comments (2) View Comments

    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.


    Most Recent Comments
    Doug Kaye 09/01/03 04:37:01 PM EDT

    Ah...the URL didn't come through. See http://www.rds.com/doug/weblogs/2003/09/01.html.

    Doug Kaye 09/01/03 04:35:55 PM EDT

    I've just posted a response to a response to this article on my weblog.

    @ThingsExpo Stories
    Join IBM November 1 at 21st Cloud Expo at the Santa Clara Convention Center in Santa Clara, CA, and learn how IBM Watson can bring cognitive services and AI to intelligent, unmanned systems. Cognitive analysis impacts today’s systems with unparalleled ability that were previously available only to manned, back-end operations. Thanks to cloud processing, IBM Watson can bring cognitive services and AI to intelligent, unmanned systems. Imagine a robot vacuum that becomes your personal assistant tha...
    SYS-CON Events announced today that TidalScale 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. TidalScale is the leading provider of Software-Defined Servers that bring flexibility to modern data centers by right-sizing servers on the fly to fit any data set or workload. TidalScale’s award-winning inverse hypervisor technology combines multiple commodity servers (including their ass...
    As hybrid cloud becomes the de-facto standard mode of operation for most enterprises, new challenges arise on how to efficiently and economically share data across environments. In his session at 21st Cloud Expo, Dr. Allon Cohen, VP of Product at Elastifile, will explore new techniques and best practices that help enterprise IT benefit from the advantages of hybrid cloud environments by enabling data availability for both legacy enterprise and cloud-native mission critical applications. By rev...
    Infoblox delivers Actionable Network Intelligence to enterprise, government, and service provider customers around the world. They are the industry leader in DNS, DHCP, and IP address management, the category known as DDI. We empower thousands of organizations to control and secure their networks from the core-enabling them to increase efficiency and visibility, improve customer service, and meet compliance requirements.
    With major technology companies and startups seriously embracing Cloud strategies, now is the perfect time to attend 21st Cloud Expo October 31 - November 2, 2017, at the Santa Clara Convention Center, CA, and June 12-14, 2018, at the Javits Center in New York City, NY, and learn what is going on, contribute to the discussions, and ensure that your enterprise is on the right path to Digital Transformation.
    SYS-CON Events announced today that N3N will exhibit at SYS-CON's @ThingsExpo, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. N3N’s solutions increase the effectiveness of operations and control centers, increase the value of IoT investments, and facilitate real-time operational decision making. N3N enables operations teams with a four dimensional digital “big board” that consolidates real-time live video feeds alongside IoT sensor data a...
    Amazon is pursuing new markets and disrupting industries at an incredible pace. Almost every industry seems to be in its crosshairs. Companies and industries that once thought they were safe are now worried about being “Amazoned.”. The new watch word should be “Be afraid. Be very afraid.” In his session 21st Cloud Expo, Chris Kocher, a co-founder of Grey Heron, will address questions such as: What new areas is Amazon disrupting? How are they doing this? Where are they likely to go? What are th...
    In his Opening Keynote at 21st Cloud Expo, John Considine, General Manager of IBM Cloud Infrastructure, will lead you through the exciting evolution of the cloud. He'll look 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 ...
    Digital transformation is changing the face of business. The IDC predicts that enterprises will commit to a massive new scale of digital transformation, to stake out leadership positions in the "digital transformation economy." Accordingly, attendees at the upcoming Cloud Expo | @ThingsExpo at the Santa Clara Convention Center in Santa Clara, CA, Oct 31-Nov 2, will find fresh new content in a new track called Enterprise Cloud & Digital Transformation.
    SYS-CON Events announced today that NetApp has been named “Bronze Sponsor” of 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. NetApp is the data authority for hybrid cloud. NetApp provides a full range of hybrid cloud data services that simplify management of applications and data across cloud and on-premises environments to accelerate digital transformation. Together with their partners, NetApp emp...
    Smart cities have the potential to change our lives at so many levels for citizens: less pollution, reduced parking obstacles, better health, education and more energy savings. Real-time data streaming and the Internet of Things (IoT) possess the power to turn this vision into a reality. However, most organizations today are building their data infrastructure to focus solely on addressing immediate business needs vs. a platform capable of quickly adapting emerging technologies to address future ...
    Most technology leaders, contemporary and from the hardware era, are reshaping their businesses to do software. They hope to capture value from emerging technologies such as IoT, SDN, and AI. Ultimately, irrespective of the vertical, it is about deriving value from independent software applications participating in an ecosystem as one comprehensive solution. In his session at @ThingsExpo, Kausik Sridhar, founder and CTO of Pulzze Systems, will discuss how given the magnitude of today's applicati...
    As popularity of the smart home is growing and continues to go mainstream, technological factors play a greater role. The IoT protocol houses the interoperability battery consumption, security, and configuration of a smart home device, and it can be difficult for companies to choose the right kind for their product. For both DIY and professionally installed smart homes, developers need to consider each of these elements for their product to be successful in the market and current smart homes.
    SYS-CON Events announced today that Avere Systems, a leading provider of enterprise storage for the hybrid cloud, 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. Avere delivers a more modern architectural approach to storage that doesn't require the overprovisioning of storage capacity to achieve performance, overspending on expensive storage media for inactive data or the overbui...
    Widespread fragmentation is stalling the growth of the IIoT and making it difficult for partners to work together. The number of software platforms, apps, hardware and connectivity standards is creating paralysis among businesses that are afraid of being locked into a solution. EdgeX Foundry is unifying the community around a common IoT edge framework and an ecosystem of interoperable components.
    SYS-CON Events announced today that Avere Systems, a leading provider of hybrid cloud enablement solutions, 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. Avere Systems was created by file systems experts determined to reinvent storage by changing the way enterprises thought about and bought storage resources. With decades of experience behind the company’s founders, Avere got its ...
    High-velocity engineering teams are applying not only continuous delivery processes, but also lessons in experimentation from established leaders like Amazon, Netflix, and Facebook. These companies have made experimentation a foundation for their release processes, allowing them to try out major feature releases and redesigns within smaller groups before making them broadly available. In his session at 21st Cloud Expo, Brian Lucas, Senior Staff Engineer at Optimizely, will discuss how by using...
    In this strange new world where more and more power is drawn from business technology, companies are effectively straddling two paths on the road to innovation and transformation into digital enterprises. The first path is the heritage trail – with “legacy” technology forming the background. Here, extant technologies are transformed by core IT teams to provide more API-driven approaches. Legacy systems can restrict companies that are transitioning into digital enterprises. To truly become a lead...
    SYS-CON Events announced today that CAST Software 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. CAST was founded more than 25 years ago to make the invisible visible. Built around the idea that even the best analytics on the market still leave blind spots for technical teams looking to deliver better software and prevent outages, CAST provides the software intelligence that matter ...
    SYS-CON Events announced today that Daiya Industry will exhibit at the Japanese Pavilion 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. Ruby Development Inc. builds new services in short period of time and provides a continuous support of those services based on Ruby on Rails. For more information, please visit https://github.com/RubyDevInc.