Wednesday, May 29, 2013

Future Proof by Design: Loose Coupling and Ensuring Long Term Success

Technical future proofing assumes constant change in both operational environments and technology.  The impacts of change are mitigated by emphasizing versatility and adaptability in system architecture.  This tenet applies equally to both hardware and software systems.  By ensuring that system components are modular, and that they interact using standard interface patterns and in a loosely coupled manner, components can be modified or readily swapped for more capable variants across the entire system lifecycle.  As a result, the system as a whole remains functional and useful well past the time when the original configuration has become obsolete.  This article illustrates risks associated with inadequate future proofing and provides an overview of tools and techniques that promote long lasting, future proofed software systems.

The Parable of the Joint Strike Fighter

F-35 C-Variant Testing; courtesy of
During a sidebar conversation at the recent DC Open SourceCommunity Summit, a lively discussion ensued concerning the troubled F-35 JointStrike Fighter (JSF) program.  The JSF program began in 2001, with a projected budget of $233 billion and an estimated initial operational capability (IOC) taking place between 2010 and 2012.  As chronicled by Government Accountability Office (GAO) in a report published on April 17, 2013, the program’s price tag is now nearing $400 billion and IOC is not expected until 2017 or 2018. 

During testimony before the US Congress on April 24, 2013, the JSF Program Manager, US Air Force Lieutenant General Christopher Bogdan, indicated that problems with the JSF’s complex softwaresuite created risks to the 2017 IOC date.
The ever expanding numbers and constantly slipping dates do not cast either the defense acquisitions community or industry in the most flattering light.  However, righteous taxpayer anger and legislators’ ire masks what may be the most troubling aspect of the JSF lifecycle. Specifically, the JSF may be operationally obsolete by the time it is delivered to combat squadrons.  In the twelve years since program inception, armaments developments in both the United States and abroad may render the aircraft significantly less effective than planned.

In 2010, it was reported that the People’s Republic of China had deployed the Dong-Feng (DF) 21D mobile medium-range ballistic missile(MRBM).  The DF-21D, with a 1,500 nautical mile range, is designed to target and destroy aircraft carriers.  The threat to the JSF’s utility is clear:  The F-35 has a combat radius of approximately 600 nautical miles.  Carriers operating F-35s in a hostile Pacific Rim would have to steam through – and then loiter within – a danger zone of approximately a thousand miles in order to deploy their strike aircraft.

More recently, on May14, 2013, the Associated Press reported that, for the first time ever, the US Navy had launched an unmanned aircraft from an aircraft carrier at sea.  The stealthy aircraft, called the X-47B, is capable of speeds approaching Mach 1 (it’s officially described as “high subsonic”), has a range in excess of 2,100 nautical miles, contains internal weapons bays and is expected to serve as the prototype for the Unmanned Carrier Launched Airborne Surveillance and Strike System (UCLASS).  UCLASS is expected to enter service in 2019.  

The UCLASS’ existence raises uncomfortable questions about the JSF:  Why is a relatively short ranged manned aircraft, whose limitations expose expensive and vulnerable capital ships to catastrophic danger necessary when a long range, stealthy, unmanned platform is available to complete many of the same missions?

The fact that the JSF program wasn’t future proofed from an operational perspective isn’t surprising.  It isn’t realistic to expect accurate technological (or budgeting) predictions a decade in advance (the X-47B first flew in 2011).  What is surprising is that the program wasn’t designed from a componentized, modular perspective that would have guaranteed continued relevance and capability.  Instead, the F-35 is a tightly integrated package representing the state of the conceptual art responding to operational concerns of the very early 21st century.

Software and Future Proofing

The issues and architectural requirements attendant to future proofing aren’t unique to hardware in general or weapon systems in particular.  Many legacy software systems suffer from similar issues stemming from monolithic, tightly coupled designs suited explicitly for one or more specific clearly defined purposes.  Unfortunately, these design paradigms result in heavy sustainment burdens, vendor lock-in situations and difficulties with adaptation.

Fortunately for software acquisitions program managers, industry has evolved architectural paradigms intended to alleviate software future proofing concerns.  Examples of these paradigms are service oriented architectures (SOA) and Cloud computing concepts such as software as a service (SaaS) and platforms as a service (PaaS).  However, at the heart of all of these future proofing methodologies is a design tenet known as “loose coupling.”

“Coupling” is a technical term of art that refers to the degree of direct knowledge that system components need to have of one another in order to interoperate.  Loose coupling is a design tenet that ensures that minimizes dependencies between a system’s components to the least practical extent.  Its objective is to eliminate the impact a change on one component has on the rest of the system.  Limiting the number of interconnections between components through adherence to loose coupling principles brings long term benefits such as easier problem isolation, simplified testing and lower maintenance and sustainment costs.

The extent of a system’s coupling can be measured in terms of the degree to which a component can be changed without adverse effects to the rest of the system.  Such changes might include adding, removing, renaming or reconfiguring components or modifying a component’s internal characteristics or the way it interfaces with other components.  The more readily individual components can be modified or swapped without impacting the rest of the system, the greater the degree of loose coupling.  With respect to future-proofing, greater degrees of loose coupling translate to more efficient and less costly modifications, with shorter cycle times, to account for changing requirements.  Greater degrees of loose coupling equate to greater future proofing.

Loose Coupling Tools and Components

There are many ways to enhance loose coupling.  For example, data exchanges could mandated to use a flexible data format such as XML or JSON that allows subscribers to publish the definitions of how to use the data as a schema.  Another method is to use dedicated middleware that allows for the isolation of system components.  Within the SOA paradigm, there are three widely used middleware tools that promote loose coupling:  The enterprise service bus (ESB), the data service and the message broker.  A brief explanation of each of these is worthwhile.


The ESB is a software component that provides data transport, transformation and mediation services between interoperating software services, applications and components within a heterogeneous and complex application landscape.  All interactions between system components take place through the ESB, isolating the components from one another.  As a result, changes to a component are confined to the component and any mediation adapters within the ESB that transform the component’s outputs into formats useful to the rest of the system.  All other system components are shielded from the change.  In addition to their integration capabilities, ESBs also provide services such as routing, gateway functionality for messages, services, application programming interfaces (API) and security and monitoring.  Many vendors provide ESB offerings.  Interestingly some of the most capable are also open source, such as the WSO2 ESB, the Mulesoft ESB and OpenESB.

Data Services

Data services are integration mechanisms addressing the challenges of heterogeneous and disparate data stores that underlie legacy application integration efforts.  Rather than requiring a lengthy and expensive data migration and normalization effort, architects can integrate legacy, external and objective data stores using data services that retrieve and expose data as web services or REST resources.  These data services provide loose coupling between the data stores and the rest of the system.  Changes to either a data store or a data consumer are isolated by the data service.
Moreover, the data that data services expose is not limited to traditional SQL relational database management systems (RDBMS).  NoSQL databases, CSV/Excel files, RDF triplestores/quadstores and web page scrapes can all serve as data sources.  Data services can also integrate security concepts such as authentication, authorization, confidentiality, integrity and encryption using open standards such as Basic Authorization over HTTPS, WS-Security, WS-Trust, WS-Secure Conversation, WS-Policy, WS-PolicyAttachment and WS-SecurityPolicy.  Typical of data service implementation tools (and also open source) is the WSO2 Data ServicesServer.

Message Broker

Message brokers sit between components, mediating communication and providing loose coupling by minimizing the awareness that components need to have of each other in order to be able to exchange messages.  Many message brokers also provide temporal decoupling, allowing for asynchronous communications.  At its most basic, a broker takes incoming messages from applications and provides some form of communications mediation, such as:

  • Message routing;
  • Message distribution;
  • Support for both request-response and publish-subscribe messaging.

If these seem similar to the capabilities offered by an ESB, it’s because they are.  Message brokers and ESBs have different technological roots, but have some overlap in the capabilities they provide.  There are, however a couple of basic differences.  A message broker (generally) provides only message distribution capabilities, either in the form of queues (for single consumers) or topics (for event distribution/multiple consumers).  An ESB can work with a message broker or use more direct messaging mechanisms such as HTTP.  Additionally, ESBs generally provide content mediation and transformation capabilities.  Unfortunately, there isn’t an industry standard for where an ESB ends and a message broker begins.  Open source message brokers include the Fuse Message Broker, the WSO2 Message Broker and Mosquitto.

Loose Coupling and Future Proofing

In the end, future proofing is about ensuring that a delivered system is readily adaptable with respect to changing technologies, changing missions and changing operational environments.  There are a number of requirements implicit to adaptability:
  • The system must be functionally modifiable such that it can complete missions for which it was not originally designed;
  • The cost of modification must be kept to a minimum; and
  • The time required for the modification must be kept to a minimum.
Following the chain to its logical conclusion future proofing equates to adaptability equates to loose coupling!  While the F-35 may be both operationally and technically tightly coupled, the wide availability of middleware tools promoting decoupling – many of them open source – ensure that military and government software programs do not have to be. 

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