software architecture: basic concept
DESCRIPTION
SOFTWARE ARCHITECTURE: BASIC CONCEPT. By Xiangzhe Li Thanh Nguyen. OUTLINE. Introduction Terminology Architecture Component Connector Configuration Architectural Style Architectural Pattern Model Processes Stakeholders Conclusion. INTRODUCTION. Main idea of this chapter: - PowerPoint PPT PresentationTRANSCRIPT
SOFTWARE ARCHITECTURE:
BASIC CONCEPT
By Xiangzhe Li
Thanh Nguyen
OUTLINE Introduction Terminology
Architecture Component Connector Configuration Architectural Style Architectural Pattern
Model Processes Stakeholders Conclusion
INTRODUCTION
Main idea of this chapter:
Define the key terms & ideas from the field of software architecture.
Provide a uniform basis for their discussion in the remainder of the book.
Architecture
Definition:A software system’s architecture is the
set of principal design decisions made about the system.
The architecture is the blueprint for the construction and evolution of the system.
Architecture (Continue)
Design decisions are involved in every aspect during the construction of the system:
Structure Behavior Interaction Nonfunctional Implementation
Cwm - data processing software for the semantic web
Principal Definition: Principal implies a degree of importance
that grants a design decision architectural status.
Not all design decisions impact a system’s architecture.
Ex: Algorithm and data structure
Prescriptive vs. Descriptive
Prescriptive architecture represents how the system is intended characteristics and functionalities that are prior to the construction.
Descriptive architecture represents how the system is actually realized after the implementation.
Prescriptive vs. Descriptive (Continue)
Prescriptive architecture is modified during the development of the system due to several factors:
Accommodate actual requirements Code optimization Inadequate techniques and tool support
This leads to ...
Architectural Degradation Architectural drift:Introduction of principal design decisions into a system’s descriptive architecture that - Was not included by the prescriptive
architecture.- Do not violate any of the prescriptive
architecture’s design decisions. Architectural erosion:Introduction of architectural design decisions into a system’s descriptive architecture that violate its prescriptive architecture.
Other Definitions
Perry and WolfArchitecture = {elements, form, rationale}
ANSI/IEEE standard 1471-2000Fundamental organization of a system, embodied in its components, their relationships to each other and the environment, and the principles governing its design and evolution
Chris VerhoefThe software architecture of deployed software is determined by those aspects that are the hardest to change
Component
Definition: An architectural entity that 1) Encapsulates a subset of the system’s
functionality and/or data2) Restricts access to that subset via an
explicitly defined interface3) Has explicitly defined dependencies on its
required execution context
Note: components are usually application specific
Other definition
Clemens SzyperskiA software component is a unit of composition with contractually specified interfaces and explicit context dependencies only. A software component can be deployed independently and is subject to composition by third parties.
Connector
Definition:A software connector is an architectural element tasked with effecting and regulating interactions among components.Examples of connectors: Procedure call connectors Shared memory connectors Distribution connectors
Procedure call connectors
Simplest and widely used type Directly implemented in programming
languages Enable synchronous exchange of data
and control between components Caller to callee relationship
Shared memory connectors
Allow multiple software components to interact by reading from and writing to the shared facilities.
All writers and readers does not depend on each other to perform its tasks.
Distribution connectors
Encapsulate network library application programming interfaces (API)
Enable components in a distributed system to interact
Joined with multiple basic connector to separate the interacting components from the system distribution details
Key Terms
Architecture Design decisions Principal Prescriptive architecture Descriptive architecture Architectural drift Architectural erosion Component Connector