Executable Representations

Each EPIC iteration assembles an Executable Representation of the solution that exhibits the common understanding of the solution that has been achieved among affected stakeholders to that point and demonstrates the adequacy of the solution to meet the iteration objectives.

An Executable Representation is computerized; as a user changes inputs, the model changes appearance or behavior

Representation is a representation or model; the user inputs affect only selected aspects of the eventual system

An executable representation is essential to reduce the risks due to misunderstandings or unforeseen technical and operational factors.

In early iterations, the Executable Representation may be a mock-up of critical stakeholder needs. In later iterations, the Executable Representation is a prototype reflecting the architecture. It may evolve to become the fielded solution. This prototype includes an ability to test the necessary infrastructure and any other systems with which the solution must interact. In addition, the Executable Representation for each phase must be sufficient to explore the end-user business processes inherent in the solution.

EPIC divides the system lifecycle into four phases matching those of RUP. The Executable Representation has different forms in each phase:

Inception	Elaboration	Construction	Transition
Build and test proof of concept(s)	Build and test an architectural prototype	Build and test the solution	Build and test releases of the solution
Demonstrate the approach to the critical use cases	Demonstrate stability in requirements and architecture	Demonstrate maturity sufficient to be fielded to users	Demonstrate continued functionality
Prototype the needed changes to the end user’s business process		Implement the needed changes to the end user’s business process
		Make any needed existing infrastructure and external interfaces changes

Varieties of Executable Representations

spreadsheet

model the business case
model network performance

HTML document with links from buttons. see The GEE example
GUI mockup built with a rapid development tool
security model: access to user permission attributes
security model: transfer of encryption keys
heuristic and pattern matching tools for expressing models and reasoning about them
decision support frameworks for studying attributes
quantitative modeling tools
architecture prototype
an experimentation facility. Installed vendor demos with system data formats
solution baseline mockup
behavioral prototypes focusing on specific behaviors of the system
structural prototypes exploring architectures or technologies
exploratory prototypes to be thrown away after you have learned whatever you wanted from them
evolutionary prototypes that evolve to become the final system