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TRANSFORM ANALYSIS. Heuristics and Rules. DFD with Transform Flow Characteristics. input-driven. center of transformation. output-driven. Structured Analysis and Design Information Flow Analysis. 1 - specify the flow of information in your system => DFD - PowerPoint PPT Presentation
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1
TRANSFORM ANALYSIS
Heuristics and Rules
2
DFD with Transform Flow Characteristics
input-driven output-drivencenter of transformation
3
Structured Analysis and DesignInformation Flow Analysis
1 - specify the flow of information in your system
=> DFD
2 - identify typical structural patterns in the DFD
=> analysed & annotated DFD
3 - use a proven heuristic to map DFD into SC
=> first SC
4 - refine and check your Structure Chart
=> final SC
4
Structured Analysis and DesignTransform Analysis
1 - specify the flow of information in your system
2 - a) confirm transform flow characteristics
b) identify the center of transformation
===> annotated DFD
3 - transform your DFD into a first Structure Chart
using IPO structure as design heuristic
4 - refine and check your Structure Chart
===> complete SC
5
Transform Analysis - Step 1
• the DFD should exist as a result of systems requirements engineering and systems analysis
• check completeness of the DFD, data dictionary, and process dictionary
• refine the DFD (decompose, etc.) if that is necessary
6
registration
read& check reg.
prepareinvoice
acceptreg.
printinvoice
writeconf.
user
user
printer
registration db
reg+
reg+reg_info
conf.
invoice
reg-profile prices
invoice_prt
conf_msg
error_msg
7
readregistration check
registration
error-handlerregistration
registration
reg+
reg+error_reason
error_msg
reg_i
8
Transform Analysis - Step 2
• Step 2a:– check the list of properties for transform
flow characteristics– be aware that this is a guideline only
• Step 2b:– find and mark the center of
transformation in the DFD
9
Transform Analysis - Step 2b
• locate the center of transformation– follow input-driven flows into the center until
the data is in an internal format, correct and complete ===> mark position
– trace back output-driven flows to the center until the data is complete and ready for presentation, but not yet in external format ===> mark position
• connect all markings: center of transformation
10
registration
read& check reg.
prepareinvoice
acceptreg.
printinvoice
writeconf.
user
user
printer
registration db
reg+
reg+ reg_info
conf.
invoice
reg-profile prices
invoice_prt
conf_msg
error_msg
center of transformation
11
readregistration check
registration
error-handlerregistration
registration
reg+
reg+error_reason
error_msg
reg_i
12 Transform Analysis - Step 3IPO mapping heuristic
i1
i2
ct1
ct2
o1 o2
o3
sys
I-ctrl P-crtl O-ctrl
i1 i2 ct1 ct2 o1 o2 o3
13
The IPO Mapping & Design Heuristic
• establish a top level main controller (system)• always introduce:
– Input-driven flow controller– transform flow controller (Processing)– Output-driven flow controller
• translate DFD processes into SC modules and hang them from the correct controller
• allocate subprocesses => submodules
14
reg. sys.
read &check
compreg.
prod.output
readreg.
checkreg.
errorhdlg.reg.
prep.inv.
acc.reg.
printinv.
writeconf.
crt db prt crt
15 Transform Analysis - Step 4• add data (and control) flows• further decompose (factor) were necessary
– user interface handling modules– error-handling modules– add initialisation & termination modules
• check quality of design:– cohesion– coupling
• reconfirm mapping with DFD
16
See ourStructure Chart Example
(Section 3c)for a completespecification of
data and control flows.
17
End of Section 3e
coming up:software design quality