Data Structure and Elements

Study Notes

The process of finalizing design specifications involves taking logical design information and turning it into a blueprint for the physical information system.
It can be paper-based or computer-based, and can be written, graphical, or a combination of both.
The format and amount of detail will be driven by the intended audience.
Good specifications should be stated simply, completely, unambiguous, and have attributes that make requirements more understandable.

Deliverables for traditional projects include a set of physical design specifications for the entire system, including detailed specifications for each separate part of the system.
Functional descriptions are included for each part of the system, along with input received and output generated for each program and its component parts.
Complete design specification is comprehensive and can be based on traditional methods or Agile methodologies.

Specification documents contain an overall system description, interface requirements, system features, nonfunctional requirements, and other requirements.
They also include supporting diagrams and models.
Computer-based requirements management tools make it easier to keep documents up to date, add additional requirements, and link related requirements.

A structure chart is a hierarchical diagram that shows how an information system is organized.
It shows how an information system is organized in hierarchical models and how parts of a system are related to each other.
It also shows the breakdown of a system into programs and internal structures of programs written in third- and fourth-generation languages.

Prototyping is used to capture design specifications, and can be evolutionary or throwaway.
Evolutionary prototyping involves modeling parts of the target system and evolving the remaining system from the prototype.
Throwaway prototyping involves developing a prototype quickly to demonstrate an unclear aspect of system design, and is often aided by CASE tools.

Agile methodologies have a different approach to design specifications, where design specifications come from code instead of verbal text descriptions.
Agile methodologies include eXtreme Programming (XP) and Rapid Application Development (RAD).
XP has four constraints that facilitate simple design: the system must communicate everything, contain no duplicate code, have the fewest possible classes, and have the fewest possible methods.

Finalizing design specifications for electronic commerce applications involves defining required fields for each page identified in the design phase.
Key features of the human-computer interface may include menu-driven navigation, lightweight graphics, form and data integrity rules, and template-based HTML.

This chapter covered the need for system design specifications and how they vary by system development methodology.
It also covered reading and understanding structure charts, the roles of prototyping and CASE tools, and how design specifications apply to Agile methodologies.
Additionally, it demonstrated how to declare design specifications for electronic commerce applications.