This phase of work is carried out by the Technical Architect. The Business Analysis must be carried out prior to this. The purpose is to complete an unambiguous and complete specification that can be handed to the programmer who can then build exactly what the Technical Architect intends. Some interaction will be required with business stakeholders, but the bulk of this work will be carried out without further interaction. Each project is different but usually the technical design will include some of the following:

• Technical assumptions/scope
• Technology stack
• Component diagram
• Sequence diagrams
• Physical data model
• Data access classes
• Services
• Integration with other systems
• Components e.g. exception handling, reporting, monitoring, audit
• Security
• Data migration specification if there is existing data to migrate

After this we will know exactly how to build the system. At this point we can review the effort required (and therefore cost) to build the system.