University:
Anglia Ruskin University
Course:
BSE1300 | Software Engineering
Academic year:

2021
Views:

221

Pages:

3
Author:

Sharookh N.

ANALYSIS MODELS-Stream Based Modelling software Engineering ___ Notes Stream-Based Modeling Data ﬂow diagram (DFD) is the diagrammatic form that is used to show how data objects are modiﬁed as they move through the system. Although it is still regarded by many as a "old school" method, it offers a distinct perspective on the system and ought to be utilized in addition to other analysis model components. DFD RULES: ● First and foremost, there should always be a process; ● Every process must generate data; ● Describe the data ﬂow or business ﬂow; Flow from top to bottom, left to right; ● Do not impose conditions; ● Every process generates data. Procedures for developing DFDS: ● Determine requirements ● Split tasks ● Model distinct activities ● Create a preliminary context diagram; Examine preliminary level n diagrams (rudimentary textual diagrams); ● Finish diagrams LEVELLING: ● DFDs are elaborated upon or divided into levels. ● Breaking down each process into smaller ones ● Continues to ﬁnd new information The dos and don'ts of data ﬂow ● A data ﬂow may occur: ● There cannot be a data ﬂow between processes,between ﬁles,between processes and external entities, or between processes and ﬁles. ● Amongst External Entities and Files DIRECTIONS FOR DRAWING A DFD ● Give stores, terminators, ﬂows, and processes names that have signiﬁcance. ● Assign a process number. ● Redraw the DFD as often as required to ensure aesthetic consistency. Exams for Accuracy ● Are any data ﬂows missing? ● Do any unnecessary data transfers exist? Are there any labels on data ﬂows that have no meaning? ● Are any procedures absent? ● Are there any leveling mistakes? ● Are there any labels for misleading processes? ● Does information about control ﬂow? ● Does the DFD accurately depict reality?