Computer Science Chapter 6 - Architectural Design

Application Architectures

• Application systems are designed to meet an organizational need.
• They tend to have a common architecture that reflects the application requirements.

Generic Application Architectures

• Can be used as a starting point for architectural design.
• Can be used as a design checklist.
• Can be used to organize the work of the development team.
• Can be used to assess components for reuse.
• Can be used as a vocabulary for talking about application types.

Examples of Application Types

• Data processing applications:
  • Data-driven applications that process data in batches without explicit user intervention during the processing.
• Transaction processing applications:
  • Data-centred applications that process user requests and update information in a system database.
• Event processing systems:
  • Applications where system actions depend on interpreting events from the system's environment.
• Language processing systems:
  • Applications where the users' intentions are specified in a formal language that is processed and interpreted by the system.

Language Processing Systems

• Accept a natural or artificial language as input and generate some other representation of that language.
• May include an interpreter to act on the instructions in the language that is being processed.
• Used in situations where the easiest way to solve a problem is to describe an algorithm or describe the system data.

Architecture of a Language Processing System

• Includes a lexical analyzer, which takes input language tokens and converts them to an internal form.
• Includes a symbol table, which holds information about the names of entities (variables, class names, object names, etc.) used in the text that is being translated.
• Includes a syntax analyzer, which checks the syntax of the language being translated.
• Includes a syntax tree, which is an internal structure representing the program being compiled.
• Includes a semantic analyzer that uses information from the syntax tree and the symbol table to check the semantic correctness of the input language text.
• Includes a code generator that 'walks' the syntax tree and generates abstract machine code.

Compiler Components

• Lexical analyzer
• Symbol table
• Syntax analyzer
• Syntax tree
• Semantic analyzer
• Code generator

Architectural Design Decisions

• Include decisions on the type of application, the distribution of the system, and the architectural styles to be used.
• Architectural design decisions affect the performance, robustness, distributability, and maintainability of a system.

Architectural Patterns

• Are a means of reusing knowledge about generic system architectures.
• Describe the architecture, explain when it may be used, and describe its advantages and disadvantages.

Key Points

• A software architecture is a description of how a software system is organized.
• Architectural patterns are used to describe the architecture, explain when it may be used, and describe its advantages and disadvantages.
• Models of application systems architectures help us understand and compare applications, validate application system designs, and assess large-scale components for reuse.
• Transaction processing systems are interactive systems that allow information in a database to be remotely accessed and modified by a number of users.
• Language processing systems are used to translate texts from one language into another and to carry out the instructions specified in the input language.