1 / 18

SDLC Phase II: Structuring System Requirements

SDLC Phase II: Structuring System Requirements. IS 582 Dr. Dania Bilal Spring 2007. Last Week: SDLC Phase II. Determining user requirements Structuring RFP based on gathered specifications of user needs Wrote specifications for certain functions Presented written specifications in class.

vidal
Download Presentation

SDLC Phase II: Structuring System Requirements

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SDLC Phase II: Structuring System Requirements IS 582 Dr. Dania Bilal Spring 2007

  2. Last Week: SDLC Phase II • Determining user requirements • Structuring RFP based on gathered specifications of user needs • Wrote specifications for certain functions • Presented written specifications in class

  3. This Week: SDLC Phase II continued • Structuring system requirements • Data Flow Diagrams (DFDs) • Analysis tool to structure user requirements in a system • Graphically represents data movement or flow in an information system and relationships among data flow

  4. DFDs • Show the processes that transform or change data • Focus on movement of data between processes • DFDs are called process models • Process modeling shows data flow through the system based on an organization’s rules, decisions, and policies

  5. DFDs • Increase software development productivity by • avoiding mistakes in representing user requirements • Saving money in software cost • Based on user requirements gathered during planning stage • Evolve from the more general to the more specific

  6. DFDs • DFDs of current system • Used to understand current system • DFDs of new logical system • Used to show data flow, structure, and functional requirements of new system

  7. DFDs Symbols • Flow of data is represented by • Data flow • Data Store • Process • Source (external entities)

  8. DFDs Symbols • Data Flow • Data in motion from one place in a system to another • Example: user query in a database

  9. DFDs Symbols • Data store • Physical location or various locations of data in an information system • Example: a data store in a circulation system contains data about students, faculty, staff, community users, etc.

  10. DFDs Symbols • Process • Actions performed on data for transformation, storage, and distribution • May represent data in • File folder, computer-based file, notebook

  11. DFDs Symbols • Source/sink • Depicts the origin and/or destination of data • Refers to a external entity • Another organization or unit that sends and receives information from the system • A person who interacts with the system, inside or outside • Another information system that exchanges information with the system under analysis

  12. DFDs Symbols • Source/sink • Defines the system boundaries • Data originates outside a system from one or more sources, and the system produces information to one or more sinks

  13. DFD Mechanics • How the four symbols are represented? • Data flow: drawn as an arrow • Data store: drawn as a rectangular • Process: drawn as a circle • Source/sink: drawn as a square

  14. DFD Definitions • Level - 0 diagram • Represents a system’s major processes, data flow, and data stores at the highest level of detail • Context diagram • Shows major flow between entities and the system (too general) • Level N diagram • A DFD that results from a decomposed Level-0 diagram

  15. Types of DFDs • Current logical • Depicts current system • New logical • Has additional functions • Inefficient data flows are reorganized

  16. DFDs • New physical • Depicts physical implementation of the new system • Examples • Visit • http://www.umsl.edu/~sauter/analysis/dfd/dfd.htm

  17. Collection Preparationis on a different set of slides

  18. Class Activity • Do a Level 0 DFD for an automation function and its tasks, using the various symbols. • Do a Level N DFD based on Level 0 • Use PPT to draw the final DFDs You may work in a group or individually.

More Related