Requirements Models to Architectural Design Models: A Simple Library Example Robert France Colorado State University

What is architectural design? Concerned with identifying subsystems and their relationships Architectural design is an example of programming-in-the-large –Basic element of construction is a subsystem or layer or system component (unlike programming- in-the-small where the basic unit of construction is a statement in a programming language) Subsystems are systematically refined to show more details in detailed design.

Architecture Types Logical Architecture –Organization of a system into logical units (e.g., layers, subsystems) –Logical units do not necessarily result in units of implementation (e.g., Java packages, components) Implementation (Deployment) Architecture –Organization of a system into physical units (e.g., source files, Java packages, components)

Layered Architectures Separate presentation and application logic, and other areas of concern. UI Layer “Domain” or “Application Logic” Layer Services Layer Persistence Subsystem Logging Subsystem...

Component Architectures An architectural component is an architectural unit provides a well defined set of services. An architecture is constructed by composing components. A component has two types of interfaces –Provided interface: describes the services provided by a component –Required interface: describes the services that the component requires to provide its services

Transitioning to Architectural Design Requirements class model Requirements use case Architectural static model Architectural sequence models Identify subsystems by grouping use cases Identify subsystems by grouping classes Describe how subsystems interact to accomplish use cases

Simple Library Example Library consists of reference and general copies –Only general copies can be chacked out; reference copies cannot be checked out A borrower cannot check out a copy if they have outstanding fines. A borrower is charged $1 for each week after its due date that it is not returned.

Library Example: required services CheckOutCopy ReturnCopy AddCopy DeleteCopy AddBorrower DeleteBorrower FindCopy

CheckOutCopy UseCase (draft form) UseCase: CheckOutCopy Main flow 1.Clerk enters borrower and copy identifiers 2.If borrower is registered, does not have fines, and copy is a general copy then system indicates that checkout is successful; else system indicates that checkout is not successful

Requirements Class Model

Architectural Static Model Use cases grouped into borrower services and administrative services; two subsystems for each of these groupings is created – one responsible for borrower services, the other for administrative services Both administrative and borrower services need copy and borrower information. This observation results in a decision to include two subsystems for managing copies and borrowers.

CheckOut Sequence Model

ReturnCopy Sequence Model