Domain-Driven Design: Tackling Complexity in the Heart of Software

A navigation map of the language of 
MODEL-DRIVEN DESIGN

---

Elaborate models can cut through complexity only if care is taken with the fundamentals,
resulting in detailed elements that the team can confidently combine.
[ Team LiB ]

---

[ Team LiB ]
Chapter Four. Isolating the Domain
The part of the software that specifically solves problems from the domain usually constitutes only
a small portion of the entire software system, although its importance is disproportionate to its
size. To apply our best thinking, we need to be able to look at the elements of our model and see
them as a system. We must not be forced to pick them out of a much larger mix of objects, like
trying to identify constellations in the night sky. We need to decouple the domain objects from
other functions of the system, so we can avoid confusing the domain concepts with other concepts
related only to software technology or losing sight of the domain altogether in the mass of the
system.
Sophisticated techniques for this isolation have emerged. This is well-trodden ground, but it is so
critical to the successful application of domain-modeling principles that it must be reviewed briefly,
from a domain-driven point of view. . . .
[ Team LiB ]

---

[ Team LiB ]
Layered Architecture
For a shipping application to support the simple user act of selecting a cargo's destination from a
list of cities, there must be program code that (1) draws a widget on the screen, (2) queries the
database for all the possible cities, (3) interprets the user's input and validates it, (4) associates
the selected city with the cargo, and (5) commits the change to the database. All of this code is
part of the same program, but only a little of it is related to the business of shipping.
Software programs involve design and code to carry out many different kinds of tasks. They
accept user input, carry out business logic, access databases, communicate over networks, display
information to users, and so on. So the code involved in each program function can be substantial.