Baseline, transition and target

An architecture changes over time. Instead of three diagrams to keep in step, one model can hold several states: the baseline you run today, transition states on the way, and the target. Each view can show any state, and iyedy works out the gap between two of them.

Three moments of one architecture

Alex Morgan's team plans to move the Claims Platform's payments to a new provider and to split the Claims Service in two. Three moments matter:

• the Baseline: what runs today, with the Claims Service calling Payments;
• a Transition: the new Payments provider live next to the old one;
• the Target: the old provider gone, the Claims Service split into Intake and Assessment.

Each state is the one before it plus its own changes: what it adds, what it removes and what it changes (a name, a technology). A state can carry a date. The facts common to all states are written once.

The working model and the states

When you draw, you work on the working model: everything the diagram holds. A state is a reading of it at one moment. Showing the target in the containers view does not copy anything: iyedy draws the view as the model is in that state.

The state bar

A diagram whose model declares states shows a state bar at the top right of the canvas:

• State shown in this view: the state the view draws, or the working model;
• Compare with: another state; what changed is marked on the drawing as new, changed or retiring.

Picking a state shows a Preview, read-only. Keep on this view saves the choice with the view, so its exports and the PDF pack show the same drawing. Show the working model in this view goes back.

A gap is always computed

iyedy never stores the difference between two states: it works it out from them each time. The gap between the baseline and the target lists the elements and relationships added, removed and changed, the work packages that deliver each change, and the changes no work package delivers yet. That last list is where a plan has holes. See Compare states and plan a roadmap.

States and versions are not the same

You can save a named version of a diagram that holds three states, and restore it later with all three. See Save and restore versions.

What this means for you

• One diagram for the whole journey. A reviewer reads the baseline and the target side by side, from the same model.
• Exports follow the state you kept on a view: a target-state slide stays a target-state slide.
• The PDF pack adds a roadmap section when the model declares states. See Create a review pack (PDF).