Modeling Systems
with Scenario Sequence Diagrams
The
Systems Engineers task is to…
…evolve a customer desire into an achievable and
deliverable product through a methodical, systematic, analytic process which
considers Operations, Performance,
Test, Manufacturing, Cost & Schedule, Training & Support, and
Disposal throughout the entire development lifecycle[1]. |
|
Systems engineering extends throughout the
project lifecycle. Requirements, Design, Concept of Operations,
Test, Users Manual, Training and Operations documents are generated, and
elaborated, at various points in this flow.
The Scenario Sequence Diagram supports and
integrates all of these. |
A
Systematic Approach
Step 1
Understand
the customer’s desires and needs.
Listen to and model their Use Cases.
Model our understanding of the Use Cases to communicate our
understanding back to the customer for validation or correction. Once the functional understanding is
achieved these are the system requirements, the requirements model. |
|
Level 0 The customers
view of the system. The Use Cases at
this level are broad, overarching.
Some might say superficial. But
if they are not understood the system will ultimately fail to be accepted by
the user.
|
Step 2
From
the system level requirements model we develop an architecture to be used to
decompose the system. Behavior,
architecture (physical and logical) and interfaces are all decomposed. The model is now a notional architectural
model, used to communicate the system to the developers. |
|
Level 1 The initial
breakout into physical or logical segments of the system.
|
Step 3
The
elaborated architecture of physical, logical and behavioral implementations
is analyzed by the developers for achievability from cost, schedule and
engineering perspectives and becomes the design document or build
specification. |
|
Level 2 These can be
considered build levels. They too,
decompose.
|
Step 4
What
is now the design model is used to test the system in a manner that links
back through the evolution of the model to the customer’s initial
desire. |
Step 5
Ultimately
the model provides the descriptions of utilization that Users Manuals and
training are derived from. |
