Software Projects
You need to deliver the following things:
•
•
•
•
•
Project Agreement (already completed)
Documentation
Code
Demonstration for Client
Presentation in Class
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Software Projects
Documentation:
• Describes the capabilities of the software product
• Explains to the end user how to use the software
• Describes to other developers the most important
classes, their members and methods.
• Due by May 14.
• It is recommended to write at least a rough draft
of the documentation before writing the code.
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Software Projects
Code:
• Programming language: C++
• Operating system: Linux (software must be
demonstrated on campus)
• Object-oriented design
• Comments
• Due by May 14 (e-mail)
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Software Projects
Demonstration for Client:
• Demonstration in Unix Lab, PC Lab, Visual
Attention Lab or client’s office
• Can be done on a team member’s laptop
• Customer will play around with the software and
try to crash it
• Code review: Every project participant will be
asked questions about her/his code and why
she/he chose that particular implementation.
• Due by May 14
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Software Projects
Presentation in Class:
• Duration for each team’s presentation: 20 minutes
• Every team member has to speak
• One person (team leader) provides overview of the
system
• Others present their part of the system, algorithms
and data structures they used, issues they
encountered, how they were resolved, etc.
• Will take place on May 1, 6, and 8.
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Software Projects
Rules:
• Each team member must implement a clearly
defined part of the software.
• No re-use of any code unless explicitly allowed
by the customer.
• It is recommended to schedule at least one
meeting with the customer during the
development process.
• Team members will evaluate each other after
project completion.
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Rationale Management
Rationale:
• What is it?
• Why should you care?
Rationale methods:
• Representing rationale
• Authoring rationale
• Accessing rationale
State of practice & research
Summary
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An Aircraft Example
A320:
• First fly-by-wire passenger aircraft
• 150 seats, short to medium haul
A319 & A321:
• Derivatives of A320
• Same handling as A320
Rationale:
• Reduce pilot training & maintenance costs
• Increase flexibility for airline
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An Aircraft Example
A330 & A340:
• Long haul and ultra long haul
• 2x seats, 3x range
• Similar handling as A320 family
Rationale:
• With minimum cross training, A320 pilots can be
certified to fly A330 and A340 airplanes
Consequence:
• Any change in these five airplanes must maintain
this similarity
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What is Rationale?
Rationale is the reasoning that lead to the system.
Rationale includes:
Issues that were addressed,
Alternatives that were considered,
Decisions that were made to resolve the issues,
Criteria that were used to guide decisions, and
Debate developers went through to reach a decision.
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Why Rationale?
Software systems are similar to passenger airplanes:
They result from a large number of decisions taken
over an extended period of time.
• Evolving assumptions
• Legacy decisions
• Conflicting criteria
 High maintenance cost
 Loss & rediscovery of information
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Rationale Helps Deal with Change
Improve maintenance support:
• Provide maintainers with design context
Improve learning:
• New staff can learn the design by replaying the
decisions that produced it
Improve analysis and design:
• Avoid duplicate evaluation of poor alternatives
• Make consistent and explicit trade-off
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Levels of Rationale
No rationale captured:
• Rationale is only present in memos, online communication,
developers’ memory
Rationale reconstruction:
• Rationale is documented in a document justifying the final
design
Rationale capture:
• Rationale is documented during design as it is developed
Rationale integration:
• Rationale drives the design
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Example: Centralized Traffic Control
Trains
S2
T1291>
Signals
S3
Track circuits
Switches
SW1
SW2
S1
<T1515
S4
• CTC systems enable dispatchers to monitor and
control trains remotely,
• CTC allows the planning of routes and re-planning in
case of problems.
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Centralized Traffic Control
CTC systems are ideal examples of rationale capture:
Long lived systems (some systems include relays
installed last century)
• Extended maintenance life cycle
Downtime is expensive (although not safety critical)
• Low tolerance for bugs
• Transition to mature technology
Initial developers are not available
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Issues
• Issues are concrete problems which usually do not
have a unique, correct solution.
• Issues are phrased as questions.
display?:Issue
How should track sections be
displayed?
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input?:Issue
How should the dispatcher input
commands?
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Proposals
• Proposals are possible alternatives to issues.
• One proposal can be shared across multiple issues.
display?:Issue
addressed by
addressed by
text-based:Proposal
The display used by the dispatcher can
be a text only display with graphic
characters to represent track segments.
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input?:Issue
addressed by
point&click:Proposal
The interface for the dispatcher could be
realized with a point & click interface.
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Consequent Issues
• Consequent issues are issues raised by the
introduction of a proposal.
display?:Issue
input?:Issue
addressed by
addressed by
text-based:Proposal
addressed by
point&click:Proposal
raises
terminal?:Issue
Which terminal emulation should be
used for the display?
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Criteria
• A criterion represent a goodness measure.
• Criteria are often design goals or nonfunctional
requirements.
display?:Issue
input?:Issue
addressed by
addressed by
text-based:Proposal
point&click:Proposal
meets
raises
addressed by
meets
fails
fails
terminal?:Issue
usability$:Criterion
The time to input commands should be
less than two seconds.
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availability$:Criterion
The CTC system should have at
least a 99% availability.
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Arguments
• Arguments represent the debate developers went
through to arrive to resolve the issue.
• Arguments can support or oppose any other part of
the rationale.
• Arguments constitute the largest part of the
rationale.
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Arguments
display?:Issue
input?:Issue
addressed by
addressed by
text-based:Proposal
point&click:Proposal
meets
raises
addressed by
meets
fails
fails
is opposed by
terminal?:Issue
usability$:Criterion
availability$:Criterion
is supported by
availability-first!:Argument
Point&click interfaces are more complex to implement than text-based interfaces. Hence, they
are also more difficult to test. The point&click interface risks introducing fatal errors in the
system that would offset any usability benefit the interface would provide.
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Resolutions
• Resolutions represent decisions.
• A resolution summarizes the selected alternative and
the supporting argument.
• A resolved issue is said to be closed.
• A resolved issue can be re-opened if necessary, in
which case the resolution is demoted.
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Resolutions
text-based&keyboard
:Resolution
resolves
resolves
display?:Issue
input?:Issue
addressed by
addressed by
text-based:Proposal
point&click:Proposal
meets
raises
addressed by
meets
fails
fails
is opposed by
terminal?:Issue
usability$:Criterion
availability$:Criterion
is supported by
availability-first!:Argument
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Representing Rationale: Issue Models
resolves
Resolution.
Issue?
is a consequence
responds
Proposal
meets +
Criterion$
fails supports +
objects to -
supports +
objects to Argument!
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Representing Rationale
Many issue models have been proposed:
• IBIS, QOC, DRL, WinWin
• Similar in their essence
• Differ in the amount of detail that can be captured
Challenges:
• Require tool support for capture and access
• Require integration with project management tools
• Require integration with methodology
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Authoring Rationale
Approaches:
• Reconstruction
• Record-and-replay
• Byproduct of development methodology
Challenges:
• Lot of information to capture
• Disruptive for developers
• Formalizing knowledge is expensive
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Accessing Rationale
Browse & search:
• Full text search allows to identify interesting nodes
• Issue model links allow the browsing of related
issues quickly
Passive & active design critique:
• Rationale can be used by knowledge based critiques
to evaluate a design
Challenges:
• Evolving terminology
• Navigation through a large flat space
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State of the Practice
Standalone issue based tools:
• QuestMap
Problem management tools:
• Work flow application tracking problems and resolutions
• Integrated with configuration management
• Some tools (e.g., ClearQuest) allow schema to be
customized
RequisitePro:
• Requirements management
• Integrated with configuration management
• Explicitly captures rationale behind change
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An example of issue database (LN IBIS database template in Domino
Lotus Notes).
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State of Research
Many solutions for representation exist and can be
tailored to a specific problem.
Progress in natural language search and in hypertext
technology make access a less critical issue.
Current challenges:
• Integration with methodology
• Integration with tools
• Overhead
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Open Issues
Formalizing knowledge is costly:
• Maintaining a consistent design model is expensive.
• Capturing and maintaining its rationale is worse.
The benefits of rationale are not perceived by current
developers:
• If the person who does the work is not the one who benefits
from it, the work will have lower priority.
• 40-90% of off-the-shelf software projects are terminated
before the product ships.
Capturing rationale is usually disruptive.
Current approaches do not scale to real problems.
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Why Software Configuration Management?
The problem:
• Multiple people have to work on software that is changing
• More than one version of the software has to be supported:
 Released systems
 Custom configured systems (different functionality)
 System(s) under development
• Software must run on different machines and operating
systems
Need for coordination
Software Configuration Management
• manages evolving software systems
• controls the costs involved in making changes to a system
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What is
Software Configuration Management?
Definition:
• A set of management disciplines within the software
engineering process to develop a baseline.
Description:
• Software Configuration Management encompasses the
disciplines and techniques of initiating, evaluating and
controlling change to software products during and after the
software engineering process.
Standards (approved by ANSI):
• IEEE 828: Software Configuration Management Plans
• IEEE 1042: Guide to Software Configuration Management
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SCM Activities
Configuration item identification
• is the modeling of the system as a set of evolving
components
Promotion management
• is the creation of versions for other developers
Release management
• is the creation of versions for the clients and users
Branch management
• is the management of concurrent development
Variant management
• is the management of versions intended to coexist
Change management
• is the handling, approval and tracking of change requests
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SCM Roles
Configuration Manager:
• Responsible for identifying configuration items. The
configuration manager can also be responsible for defining
the procedures for creating promotions and releases
Change control board member:
• Responsible for approving or rejecting change requests
Developer:
• Creates promotions triggered by change requests or the
normal activities of development. The developer checks in
changes and resolves conflicts
Auditor:
• Responsible for the selection and evaluation of promotions
for release and for ensuring the consistency and
completeness of this release
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Terminology and Methodology
What are
• Configuration Items,
• Baselines,
• SCM Directories,
• Versions, Revisions and Releases?
The usage of the terminology presented here is not strict but
varies for different configuration management systems.
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Terminology: Configuration Item
“An aggregation of hardware, software, or both, that is
designated for configuration management and treated as a
single entity in the configuration management process.”
Software configuration items are not only program code
segments but all type of documents that are produced during
development, e.g.:
•
•
•
•
•
all types of code files
drivers for tests
analysis or design documents
user or developer manuals
system configurations (e.g. version of compiler used)
In some systems, not only software but also hardware
configuration items (CPUs, bus speed frequencies) exist!
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Terminology: Baseline
“A specification or product that has been formally reviewed and
agreed to by responsible management, that thereafter serves
as the basis for further development, and can be changed only
through formal change control procedures.”
Examples:
• Baseline A: The API of a program is completely defined; the
bodies of the methods are empty.
• Baseline B: All data access methods are implemented and
tested; programming of the GUI can start.
• Baseline C: GUI is implemented, test-phase can start.
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More on Baselines
Many naming schemes for baselines exist (1.0,
6.01a, ...).
3 digit scheme:
7.5.5
Release
(Customer)
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Version
(Developer)
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Revision
(Developer)
39
Baselines in SCM
Baseline A (developmental)
All changes relative to baseline A
Baseline B (functional)
All changes relative to baseline B
Baseline C (beta test)
All changes relative to baseline C
Official Release
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Standard SCM Directories
Programmer’s Directory
• (IEEE Std: “Dynamic Library”)
• Completely under control of one
programmer.
Master Directory
• (IEEE Std: “Controlled Library”)
• Central directory of all
promotions.
Software Repository
• (IEEE Std: “Static Library”)
• Externally released baselines.
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Promotion
Central source
code archive
Release
Foo’95
Foo’98
41
Change Management
Change management is the handling of change requests.
• A change request leads to the creation of a new release.
General change process:
• The change is requested (this can be done by anyone
including users and developers).
• The change request is assessed against project goals.
• Following the assessment, the change is accepted or
rejected.
• If it is accepted, the change is assigned to a developer and
implemented.
• The implemented change is audited.
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Change Management
The complexity of the change management process
varies with the project:
• Small projects can perform change requests
informally and fast.
• Complex projects require detailed change request
forms and the official approval by one or more
managers.
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Controlling Changes
Two types of controlling change:
• Promotion: The internal development state of a
software is changed.
• Release: A set of promotions is distributed outside
the development organization.
Promote
Policy
Programmer
Promotion
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Release
Policy
Master
Directory
Software Repository
User
Release
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Change Policies
Approaches for controlling change to libraries
(Change Policies):
• Informal (good for research type environments)
• Formal approach (good for externally developed
CIs and for releases)
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Change Policies
• Whenever a promotion or a release is performed, one or more
policies apply.
• The purpose of change policies is to guarantee that each
version, revision or release (see next slide) conforms to
commonly accepted criteria.
Examples for change policies:
• “No developer is allowed to promote source code which
cannot be compiled without errors and warnings.”
• “No baseline can be released without having been beta-tested
by at least 500 external persons.”
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Version vs. Revision vs. Release
Version:
• An initial release or re-release of a configuration item
associated with a complete compilation or recompilation of
the item. Different versions have different functionality.
Revision:
• Change to a version that corrects only errors in the
design/code, but does not affect the documented
functionality.
Release:
• The formal distribution of an approved version.
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Tools for SCM
Software configuration management is normally
supported by tools with different functionality.
Examples:
• RCS: very old but still in use; only version control
system
• CVS: based on RCS, allows concurrent
working without locking
• Perforce: repository server; keeps track of
developer’s activities
• ClearCase: multiple servers, process
modeling, policy check mechanisms
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Tasks for the Configuration Managers
SCMP following the IEEE 828-1990 standard
Define configuration items
Define promote /release policies
Define responsibilities
Set up configuration management system
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