152 Software teSting interview QueStionS
(i) can you explain ftr, ilf, eif, ei, eo, eQ, and gsc?
Elements of Function Points
The following are the elements of FPA:
Internal Logical Files (ILFs)
The following are points to be noted for ILF:
ILFs are logically related data from a user’s point of view.
They reside in the internal application boundary and are
maintained through the elementary process of the application.
ILFs can have a maintenance screen but not always.
Note: Do not make the mistake of mapping a one-to-one relationship between
ILFs and the technical database design. This can make FPA go very wrong.
The main difference between ILFs and a technical database is an ILF is a
logical view and a database is a physical structure (technical design). Example:
A supplier database design will have tables such as Supplier, Supplier Address,
SupplierPhonenumbers, but from the ILF point of view you will only see the
Supplier as logically they are all Supplier details.
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FIGURE 155 ILF example
teSting eStimation 153
External Interface Files (EIFs)
These files are logically related data from the user point of
view.
EIFs reside in the external application boundary.
EIFs are used only for reference purposes and are not
maintained by internal applications.
EIFs are maintained by external applications.
Record Element Type (RET)
The following points are to be noted for RETs:
An RET is a sub-group element data of ILF or EIF.
If there is no sub-group of ILF then count the ILF itself as
one RET.
A group of RETs within ILF are logically related. Most
likely with a parent-child relationship. Example: A supplier
has multiple addresses and every address can have multiple
phone numbers (see the following figure which shows a
database diagram). So, Supplier, SupplierAddress, and
SupplierPhoneNumber are a RETs.
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FIGURE 156 RET
154 Software teSting interview QueStionS
Please note the whole database is one supplier ILF as all belong to one logical
section. The RET quantifies the relationship complexity of ILF and EIF.
Data Element Types (DETs)
The following are the points to be noted for DETs counting:
Each DET should be user recognizable. For example, in
the previous figure we have kept the auto increment field
(SupplierId) as the primary key. The SupplierId field from a
user point of view never exists at all, it’s only from a software
designing aspect, so does not qualify as a DET.
DETs should be a non-recursive fields in ILF. DETs should
not repeat in the same ILF again, and should be counted only
once.
Count foreign keys as one DET. SupplierId does not qualify
as a DET but its relationship in the SupplierAddress table is
counted as a DET. So Supplierid_fk in the SupplierAddress
table is counted as a DET. The same holds true for
“Supplieraddressid_fk”.
File Type References (FTRs)
The following points are to be noted for FTRs:
An FTR is a file or data referenced by a transaction.
An FTR should be an ILF or EIF. So count each ILF or EIF
read during the process.
If the EP is maintained as an ILF then count that as an FTR.
So by default you will always have one FTR in any EP.
External Input (EI)
The following are points to be noted for EIs:
EIs are dynamic elementary processes in which data is
received from the external application boundary. Example:
User interaction screens, when data comes from the User
Interface to the Internal Application.
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teSting eStimation 155
EIs may maintain the ILF of the application, but it’s not a
compulsory rule.
Example: A calculator application does not maintain any data,
but still the screen of the calculator will be counted as EI.
Most of the time user screens will be EI, but again it’s not a
hard and fast rule. Example: An import batch process running
from the command line does not have a screen, but still
should be counted as EI as it helps pass data from the external
application boundary to the internal application boundary.
External Inquiry (EQ)
The following are points to be noted for EQs:
An EQ is a dynamic elementary process in which result data
is retrieved from one or more ILF or EIF. In this EP some
input requests have to enter the application boundary. Output
results exits the application boundary.
EQ does not contain any derived data. Derived data means
any complex calculated data. Derived data is not just mere
retrieval data but are combined with additional formula to
generate results. Derived data is not part of ILF or EIF, they
are generated on the fly.
EQ does not update any ILF or EIF.
EQ activity should be meaningful from a user perspective.
EP is self-contained and leaves the business in a consistent state.
DET and processing logic is different from other EQs.
Simple reports form good a base for EQs.
Note: There are no hard and fast rules that only simple reports are EQs. Simple
view functionality can also be counted as an EQ.
External Output (EO)
The Following are points to be noted for EOs:
EOs are dynamic elementary processes in which derived data
crosses from the internal application boundary to the external
application boundary.
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156 Software teSting interview QueStionS
EO can update an ILF or EIF.
The Process should be the smallest unit of activity that is
meaningful to the end user in business.
EP is self-contained and leaves the business in a consistent
state.
DET is different from other EOs. So this ensures that we do
not count EOs twice.
They have derived data or formulae calculated data.
The major difference between EO and EQ is that data passes across the
application boundary.
Example: Exporting accounts transactions to some external file format such
as XML or some other format, which later the external accounting software
can import. The second important difference is that EQ has non-derived data
and EO has derived data.
General System Characteristics (GSC) Section
This section is the most important section. All the previously discussed sections
relate only to applications. But there are other things also to be considered
while making software, such as are you going to make it an N-Tier application,
what’s the performance level the user is expecting, etc. These other factors
are called GSCs. These are external factors which affect the software and
the cost of the software. When you submit a function point to a client, he
normally will skip everything and go to the GSC section first. The GSC gives
us something called the VAFs (Value Added Factors).
There are 14 points associated with (VAFs) and the associated
rating tables:
Data Communications
How many communication facilities are there to aid in the transfer or exchange
of information with the application or system?
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