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