Software Architecture

Software Architecture

1. Set of software structures needed to reason about the system

   • Categories
     • Module
       • Implementation units
       • Specific computational responsabilities
       • In large projects are divided into sub-teams
       • Decomposition Structure, Uses Structure, Layer Structure, Class Structure, Data Model
     • Component and Connector
       • Interaction between elements at runtime to carry out system's functions
       • Service Structure, Concurrency Structure
     • Allocation
       • Mapping from software structures to the system's environments
       • Organizational, Developmental, Installation, Execution
       • Deployment Structure, Implementation Structure, Work Assignment Structure

2. Structure

   • Easy to identify in software
   • Powerful tool for system design
   • Set of elements held together by a relation
   • Architectural Structure
     • Supports reasoning about the system and its properties
     • Functionality achieved by the system
     • Availability in the face of faults
     • Difficulty of making specific changes
     • Responsiveness to user requests

3. Architectural abstraction let us look at the system details

   • Essential to time the complexity of an architecture

4. Can exists independently of its description or specification

5. Behaviour

   • How elements interact with each other

6. Views

   • Representation of a set of elements and the relations among them

7. Architectural Patterns

   • Delineate the element types and their forms of interaction
     • Shared-data (repository)
       • Comprises components and connectors that create, store, and access persistent data
     • Client-server
       • Components are clients and servers
       • Connectors are protocols and messages
     • Multi-tier
       • Describes how to distribute and allocate the components of a system in distinct subsets of hardware and software connected by a communication medium
     • Competence Center and Platform
       • Work is allocated to sites depending on the technical or domain expertise

8. Importance

   • Inhibit or enable a system's driving quality attributes
     • Whether a system will be able to exhibit its desired quality attributes is substantially determined by its architecture
   • Reason about and manage change
     • Local
       • Modifying a single element
     • Nonlocal
       • Multiple element modifications but leaves the architectural approach intact
     • Architectural
       • Affects the fundamental ways in which the elements interact with each other
   • Enables early prediction of system's qualities
     • If we know certain kinds of architectural decisions lead to certain quality attributes, we can make the according decisions
   • Enhances communication among stakeholders
     • Is sufficiently abstract that most nontechnical people can understand it adequately
   • Carrying Early Design Decisions
     • Decisions with enormous weight with respect to the system lifecycle
   • Defines constraints on implementation
     • The implementation must be implemented as the set of prescribed elements
     • Elements must interact with each other in the prescribed fashion
     • Elements must fulfill its responsability to the other elements
   • Dictates the structure of an organization
     • Prescribes the structure of the system being developed
   • Provide the basis for evolutionary prototyping
     • Once an architecture has been defined, it can be analized and prototyped as a skeletal system
   • Reason about cost and schedule
     • An architect must help the project manager to create cost and schedule estimates early in the project life cycle
   • Supplying a Transferable Reusable Model
     • Reuse of architectures provides tremendous leverage for systems with similar requirements
   • Using Independently Developed Components
     • Focuses on components that are likely to have been developed separately, even independently, from each other
   • Reduces design and system complexity
     • Minimize complexity, Enhance reuse, more regular and simpler designs, more capable analysis, shorter selection time, greater ineroperability
   • Foundation for training
     • Can serve as the first introduction to the system for new project members