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UNIT - V
Software Maintenance
and Software Project Measurement
5.1 : Need and Types of Maintenance
Q.1 What is software maintenance?
Ans. :
Maintenance is a process in
which changes are implemented by either modifying
the existing system's architecture or by adding new components to the system.
Q.2 Explain the need for software
maintenance Ans. The software maintenance is essential because of following reasons:
1. Usually the system requirements are
changing and to meet these requirements some
changes are incorporated in the system.
2. There is a strong relationship between system and its
environment. When a system is installed in an
environment, it changes that environment. This ultimately
changes the system requirements.
- The maintained system remains useful in their working environment.
- Maintenance is applicable to software developed
using any software life cycle model. The system.
changes and hence maintenance must be performed
in order to: a) Correct faults.
b ) Improve the design.
c) Implement enhancement.
d) Interface with other systems.
e) Adoption of environment (different hardware,
software, system features
etc.).
1) Migrate legacy software. g ) Replacement of old software by new software. These are the factors that makes cost high.
Q3 What are
maintenance? different
types of software
Ans. :
1. Corrective maintenance Means the maintenance
for correcting the software
faults.
2. Adaptive maintenance - Means maintenance for
adapting the change in environment (different
computers or different operating systems).
- Perfective maintenance
enhancing the system
requirements.
Means modifying or
meet the new
- Preventive maintenance Means changes made
to improve future maintainability.
Q.4 What is software maintenance? Differentiate between perfective maintenance and preventive maintenance [RGPV: June.-10, Marks 10 ]
Ans. The software maintenance process can be
as shown Fig. Q.5.1.
- Change Request - In the maintenance process
initially the request for change is
made.
5- Software Maintenance & Software Project Measurement iv) Hardware changes
v) Data conversion should be described.
Q.6 Explain various problems that may arise
- Change management - In this phase the status of during software maintenance process
all the change requests is identified,
described.
·
3. Impact analysis performed in this phase. Following activities Ans. :
1. Changes in the software are
i) Identify all systems and system
products
affected by a change request. ii ) Make an estimate of the resources needed to effect the change. iii) Analyze the benefits of the change.
4. System release planning In this phase
the schedule and contents of software release is planned. The
changes can be made to all types of software maintenance.
5. Change implementation - The
implementation of changes can be done by first
designing the changes, then coding for these changes and
finally testing the changes. Preferably the
regression testing must be performed while
testing the changes.
- System release - During the software
release i) Documentation ii) Software iii )
Training
are not well
documented. Hence it
becomes difficult to trace the
evolution of software through many versions or releases.
- Sometimes it becomes difficult to trace the
process through which the software was
created 3. While maintaining the software it is difficult to understand someone else's program.
4. Most of the software is not designed for at
change. In other words the change in the software
is not at all possible and needs to redesign it.
The software posses unstructured code.
Maintenance programmers have insufficient
knowledge of the system or problem
domain.
Appropriate documentation does not
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What 0. 5.2: Software Configuratio n are
Management
(SCM)
the objectives and features upported by software configuration management? [ RGPV: June-16, Marks 3] Ans: The software
configuration management is concerned with managing the changes in the
evolving
software.
If the changes are not controlled at all then this stream of uncontrolled change can cause the well-running
software project into
chaos.
Hence it is essential to i) Identify these changes ii ) Control the
changes iii) Ensure that
the changes are
properly implemented and iv) Report these
that begin when a software
development project begins and
terminates when the software is taken
out of operation. Q.9 What is SCM? Explain the concept of baseline and SCM items in brief. [RGPV May-18, Marks 7] Ans.: SCM : Refer Q.
BaseLine: The IEEE (IEEE Std.
No. 610.12-1990)
defines a baseline as: "A specification or product that has been formally
reviewed and agreed upon , that
thereafter serves
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Software Maintenance &
Software Project Measurement
as the basis for further development,
and that can be changed only
through formal change control
procedures".
A baseline is a milestone in the
development of software that is marked
by the delivery of one or more
software configuration items and the
approval of them is obtained through
formal technical review
The baseline is the shared project
database. It is an SCM task to
maintain the integrity of the set of
artifacts.
The elements of a design model have
been first documented and reviewed.
From this design model errors are identified and corrected. Once all parts of the model have been reviewed, corrected
and then approved, the design model
becomes a baseline.
- Further changes to the program
architecture (which is actually
documented in the design model) can
be made only after each has been
evaluated and approved.
SCM Items : Examples of Software Configuration Items are
- Computer programs Source programs Executable programs
- Documents describing the programs technical manual users manual
- Data
Program components or
functions
External data File structure
e Change control is an essential step in lifecycle. The change control can be carried out using following steps
A change request initiates a change
- The configuration object is 'checked out' of the database.
- The changes are applied to the object 4. The object is then 'checked in' to the database where automatic version control is applied. 4. Configuration audit In order to ensure change has been properly implemented or not two activities are carried out
- Formal Technical Review
- Software Configuration Audit In the formal technical review, the correctness of configuration object identified and corrected. It is conducted by technical reviewer. The software configuration audit assesses the configuration object for the characteristics that are not
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5- Software Maintenance & Software Project Measurement reviewed in formal technical review. It is conducted by the Software Quality Assurance group.
5. Status reporting The status reporting focuses on communication of the
changes to all people in an
organization involved
with the changes. 5.4: Version Control , Change Control
and Reporting
Q.11 What are the problems encountered with uncontrolled change management?
[RGPV: June-17, Marks 2] Ans. Following problems are encountered with uncontrolled change management -
1) There might be the need to create support
processes for changes.
- The user need to be trained for the uncontrolled changes
3) The rollback plan must be prepared.
- Sometimes there is a need to make conversion of huge data. Q.12 What is version control in project? [RGPV: Dec.-15, Marks 2] OR Explain version control in detail Ans. Version is an instance of a system which is functionally distinct in some way from other system instances.
Version control works to help manage different
versions of configuration items during the development process.
The configuration management allows a user to
specify the alternative configurations of the software system by selecting appropriate version.
Certain attributes are associated with each software version. These attributes are useful in identifying the
version. For example: The attribute can be 'date',
' creator', 'customer', 'status'.
of developing mental models of a software systems
intended architecture , meaning, and behavior.
The purpose of program comprehension is to recover
high - level information about a system including: 1 ) Its structure interrelationships) (components and their
2) Its functionality (what operations are performed
on what components)
3) Its dynamic behavior (how input is transformed
to output) 5-
Software Maintenance & Software Project Measurement 4) Its rationale (how was the design
process and
what decisions have been taken )
5) Its construction, modules, documentation, and
test suites.
6) Program comprehension does not change the
subject system, nor create a new system. It is the
process of examining and understanding the object
system. 5.6 Re-engineering Q.14 What do you mean by the term software re- engineering? Why It is required? Ans. DS [ RGPV: June- 12 , Marks 10] Software re-engineering means re - structuring or re-writing part or all of the software engineering system. The software re-engineering is needed for the applications which require frequent maintenance. Advantages of software re-engineering
2.
The re-engineering allows the Reduced risk developer to eliminate certain constraints on the system. This helps in reducing the risks of failures. Reduced cost The cost of re-engineering is
often significantly less developing new software. than the costs of Source program Source code translation Reverse engineering Program documentation Modularized program Original data Program structure improvement Program modularization Data Re- engineering Structured program Re-engineered data Fig. Q.14.1 Re-engineering process activities TECHNICAL PUBLICATIONS "- An up thrust for knowledge DECODE Software
design recovery. In reverse engineering the data,
architectural and procedural information is extracted
from a source code.
The reverse engineering is required because using this
technique the dirty, ambiguous code can be converted to
clear and unambiguous specification. This specification help in understanding the source code. = Q.16 Write short note on Reverse engineering [RGPV: Dec.-18, Marks 7] Ans. Initially the dirty source code or unstructured source code is taken and processed and the code is restructured. After restructuring process the source code becomes clean. The core to reverse engineering is an activity called extract abstractions. In extract abstraction activity, the engineer must evaluate older programs and extract information about procedures, interfaces, data structures databases used. ог The output of reverse engineering process is a clear,
unambiguous final specification obtained from
unstructured source code. This final specification
helps in easy understanding of source code. Fig. Q.16.1 Reverse engineering advantages of reverse Q.17 What are the engineering process? [RGPV: June-15, 17, Marks 2 ] Ans. :
1 ) The dirty code or outdated technology can be
eliminated.
2) Improved version of the system can be created
using reverse engineering. 3 ) Documentation can be made available , once the old system gets reverse engineered. 4 ) It is cheaper than developing the system from
scratch. Q.18 What is the difference between forward engineering and reverse engineering? Ans. : Sr. Forward engineering No. Reverse engineering process in which the dirty or
unstructured code is
taken, processed and it is
restructured.
- Forward engineering is a Reverse engineering is a process in which theories, methods and tools are applied to develop a professional software product.
- Initially only user requirements are available for forward engineering process. A dirty or unstructured code is available initially. TECHNICAL PUBLICATIONS- An up thrust for knowledge DECODE
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