Page 75 - DCAP305_PRINCIPLES_OF_SOFTWARE_ENGINEERING

Unit 4: Introduction to Validation, Metrics

data creates reports or output files sent to other applications. These reports and files are created Notes
from one or more internal logical files and external interface file. The following graphic represents
on EO with 2 FTR’s there is derived information (green) that has been derived from the ILF’s.

Figure 4.2: External Outputs

EQ

ILF
Derived Data

ILF

External Inquiry (EQ): It is an elementary process with both input and output components that
result in data retrieval from one or more internal logical files and external interface files. The
input process does not update any Internal Logical Files, and the output side does not contain
derived data. The Figure 4.3 represents an EQ with two ILF’s and no derived data.

Figure 4.3: External Inquiry

EQ

ILF

ILF

Internal Logical Files (ILF’s): A user identifiable group of logically related data that resides entirely
within the applications boundary and is maintained through external inputs.

External Interface Files (EIF’s): A user identifiable group of logically related data that is used for
reference purposes only. The data resides entirely outside the application and is maintained by
another application. The external interface file is an internal logical file for another application.
After the components have been classified as one of the five major components (EI’s, EO’s,
EQ’s, ILF’s or EIF’s), a ranking of low, average or high is assigned. For transactions (EI’s, EO’s,
EQ’s) the ranking is based upon the number of files updated or referenced (FTR’s) and the
number of data element types (DET’s). For both ILF’s and EIF’s files the ranking is based upon
record element types (RET’s) and data element types (DET’s). A record element type is a user
recognizable subgroup of data elements within an ILF or EIF. A data element type is a unique
user recognizable, non recursive, field.

Each of the following tables assists in the ranking process (the numerical rating is in parentheses).
For example, an EI that references or updates two File Types Referenced (FTR’s) and has seven
data elements would be assigned a ranking of average and associated rating of 4. Where FTR’s

LOVELY PROFESSIONAL UNIVERSITY 69