November 26, 2010
Domain analysis is a foundational capability required for effective systematic reuse. Why? There are a lot of applications your teams are working on and the common theme among them most likely is the fact that they are in the same problem domain. In order to truly bring down cost of new applications and services, it is critical that the domain is understood and modeled appropriately. Here are some specific strategies to make this idea operational:
- Account for domain analysis and modeling in your iteration planning. Domain analysis is necessary to understand the nuances and variation points that an application/service/process needs to realize. Discovering the right variations requires time and interactions with business stakeholders and subject matter experts.
- Aspire for a core set of business object definitions that can be shared across business processes and service interfaces. Without appropriate data governance, domain knowledge will either be inaccurate/incomplete or worse duplicated in an inconsistent fashion. As the number of customer interfaces increase for your services, the domain inconsistencies will lead to greater point-to-point integrations and complexity.
- Align overall architecture with domain variations. Your domain is rich and complex but probably varies in a known set of ways. Additionally, what varies isn’t uniform and the rate of change across these variations aren’t identical. This is significant because the variations in the domain need to be captured in your overall architecture. Products/applications in the domain need to share a common architecture – only then can components integrate and inter-operate and systematic reuse will take hold. Constantly evaluate the need for a new version of a core business entity and associated classes to manage the entity.
- Refactor constantly to get to intention revealing design and code. As Eric Evans illustrates in Domain Driven Design, intention revealing code is easier to understand and evolve. It also makes it easier to address new business requirements – as the design/implementation are closely aligned with the business domain, the quality of communication (referred to as ubiquitous language) and the ability to change it both increase significantly.
This isn’t an exhaustive list – instead, it is meant to highlight the need for placing the domain in the middle of every design, architecture, and implementation decision your teams make.
November 13, 2010
New episode added to the Software Reuse Podcast Series on designing reusable exception handling for SOA efforts. It elaborates on using a simple set of components for handling exceptions, capturing relevant metadata, and determining notifications.
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November 6, 2010
Use Maven Assemblies for Packaging Configuration Artifacts
The maven assembly plugin can be used to generate separate artifacts for environment-specific configuration files. This is very useful to separate binaries (jar, war, etc.) from configuration (xml, properties files, etc.). This enables deployment of a binary across any environment. Reusable components are often used in several applications and processes and they often have configuration information. Your clients will want to customize the configuration for testing/altering behavior and it is critical that your build process separates binaries from configuration.
Here’s the snippet for adding the plugin in the POM file:
Here’s an example packaging a zip:
November 6, 2010
When working on implementing business process automation solutions, the team needs to bring together several related concepts: chief among them are events, process instances, and service capabilities. I like to think of them in the context of an overall enterprise architecture being aligned with individual solutions and projects. Bringing these concepts together holistically has several benefits:
- Better alignment between BPM & SOA initiatives (wrote earlier about the risks of not doing so)
- Consistent interfaces for event producers and consumers (e.g. clients who initiate changes to data or alter a process will be able to reuse a standardized set of messages)
- Simpler solution architecture – aligning data models across event processing and services will reduce data transformation needs. It will greatly reduce the need for data mapping and complex adapters.
Events can be internal or external and can impact business processes in several ways. An external event could initiate a business process (thereby a new process instance is created), or alter an existing process (execution is moved from some kind of wait state or an existing instance could be terminated). These events could be data, state, or a combination of the two impacting a business process. The business process instance might take an alternate path or spawn a new instance of another process as appropriate.
Process instances themselves can be implemented by leveraging several service capabilities. These service capabilities need to share a consistent set of domain-relevant interfaces. The process instances can then be loosely coupled with services thus enabling the service implementations to evolve over time. As state changes happen in a process instance, outbound events can be generated – these are publications or notifications that are of interest to potentially multiple consumers. Service capabilities can be leveraged for not just creating/changing data but also when encapsulating business rules for decision steps, as well as for publishing messages to downstream systems/processes.