In the evolving landscape of enterprise application development, built-on applications have emerged as a superior strategy for achieving scalable reuse, architectural clarity, and operational efficiency. Unlike traditional packaged components, built-on applications offer a hierarchical structure, complete encapsulation, and subject area orientation that align seamlessly with enterprise architecture principles. This article explores the architectural, operational, and organizational advantages of built-on applications—highlighting their role in enabling sophisticated versioning, distributed ownership, and seamless DevOps integration—making a compelling case for their adoption as the foundation of modern enterprise solutions.

Built-on applications offer strategic advantages for enterprise reuse that make them superior to packaged components, including hierarchical structure, complete encapsulation, subject area orientation, sophisticated versioning, distributed ownership, better application layering, and seamless DevOps integration. Below are the details.

1. Architectural Advantages

1.1 Hierarchical Application Structure

Built-on applications create a structured hierarchical tree that Pega automatically converts into a linear application stack. This architecture enables:

• More cohesive organization of functionality,
• Clearer inheritance models than isolated rulesets,
• The ability to break up common components into separate applications,
• Pointing applications to other application rules.

1.2. Encapsulation and Self-Containment

One of the most compelling advantages of built-on applications is their complete encapsulation:

• All necessary elements are contained within each application: data models, integrations, processes, UI components,
• Each subject area (Account, Customer, Credit) can be developed, maintained, and enhanced independently,
• Unlike packaged components which focus on specific features, built-on applications allow defining work and data classes at each layer,
• Pattern and Directed inheritance from classes in lower layers creates comprehensive enterprise solutions.

1.3. Subject Area Orientation

The recommended approach organizes reusable assets by subject areas:

• Each subject area implemented as a complete built-on application,
• Enables specialized teams to develop deeper domain expertise,
• Results in coherent and comprehensive reusable components,
• Facilitates clearer organization by business domain.

1.4. Multi-Layer Application Stack

The recommended application stack structure includes:

• Self-contained subject area applications (Account, Customer, Credit, etc.) as the foundation,
• Business application layers built on top of these foundation components,
• Implementation layers for specific customizations,
• This layered approach provides greater flexibility than packaged components while ensuring core functionality remains consistent across implementations.

2. Operational Benefits

2.1. Sophisticated Version Management

Built-on applications provide superior versioning capabilities:

• Consumers have flexibility to choose when to adopt new versions,
• Changes must be tested in Development and QA environments before promotion,
• Specific versioning strategies allow consumers to either:
  • Automatically receive latest updates,
  • Remain on stable versions until ready to upgrade.

2.2. Automatic Propagation of Enhancements

When using built-on applications:

• Enhancements and bug fixes automatically propagate to implementation applications,
• This automatic propagation ensures consistency across enterprise applications,
• Maintenance overhead is reduced,
• A sophisticated versioning approach (Major.Minor.Patch) gives consuming applications control over update adoption.

2.3. Consistent Deployment Pipeline Integration

Built-on applications integrate seamlessly with modern DevOps practices:

• Specific approaches for deploying reusable assets through Deployment Manager,
• More efficient creation of product files,
• Better management of component versions across environments,
• All handled more effectively through the built-on application model.

3. Organizational Alignment

3.1. Distributed Ownership Model

The built-on application approach enables more effective governance:

• Prevents single point of failure by distributing ownership,
• Applications are owned by the teams that built them,
• Maintains quality through branch-based development and code reviews,
• Allows multiple teams to contribute enhancements while maintaining clear accountability.

3.2. Enterprise Architecture Alignment

Built-on applications align better with enterprise architecture principles by enabling:

• Mapping of high-level architecture in an "Enterprise Architecture Subway Map",
• Identification of common elements like integrations and data classes,
• Organization of modules by subject area,
• Specialized teams focusing on their areas of expertise,
• This approach is more difficult to achieve with packaged components, which tend to focus on specific functionalities rather than comprehensive subject areas.

3.3. Better Support for Application Layers

The ideal layered architecture includes:

• Subject area applications forming the foundation,
• Business Application layers built on top,
• Implementation layers for specific customizations,
• This structured approach enables clear separation of concerns while maximizing reuse,
• Business Applications inherit all assets from the subject area applications.

While packaged components (rulesets) can be useful for self-contained features, built-on applications are clearly superior for enterprise reuse. Their hierarchical structure, inheritance capabilities, versioning flexibility, and alignment with enterprise architecture principles make them the preferred approach for organizations seeking to maximize reuse at scale. The recommendation is to build reusable assets as built-on applications, and even consider refactoring features initially developed as separate rulesets into built-on applications to realize the long-term advantages of this approach.