7/28/2019 Csc 302 Notes
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General & Modeling
Large means anything nontrivial that benefits from paper
planning and tools, and will be used by someoneother than the
developer
Build models to help during design, analyze existing systems,
help us communicateSoftware Architecture
avoid unnecessary coupling and cohesion - spaghetti code layered
Model View Controller, Model View Presenter Conways law:
architecture of a system tends to mirror the communication and
structure of a team. if you
structure the team in a different way, it can impact archit.
Sequence Diagrams
shows well defined order, over time. used for when looking at
different design options, elaborating on use cases alt: alternative
multiple fragments. guard condition must be true to execute loop:
may execute multiple times, as indicated by the guard neg: invalid
interaction opt: fragment is optional. works like an if condition
par: fragments run in parallel ref: reference to a interaction
that's defined in another diagram region: a critical region; only
one thread at a time.
Use Case Diagrams
captures system requirements. how users interacts with a system.
short phase to sum functionality."actors" play the roles of people.
relationships between use cases.
SDLC (Systems Development Life Cycle)
Waterfall: Requirements -> Design -> Implementation ->
Verification -> Maintenance Pros: Enforces discipline. Defined
start and end. Progress can be identified. Emphasis on
requirements
and design helps create better code/save time. Improves quality
by doing reqs and design first. Easy to
catch flaws. Easy to transfer knowledge through team.
Cons: Customers might change their mind, particularly with
requirements and design. May be past thatpoint already. Waterfall
assumes that design can be easily translated into a real product,
but developers
can run into roadblocks. If a re-design is required it can screw
the distinctions between the phases of
the model. Waterfall also suggests a clear division of labor,
etc "developers, programmers and testers"
but in reality no such division really exists.
Gantt Charts
Pros: Useful for small projects. Presents phases &
activities of project work breakdown schedule well. Cons: Wrongly
equated with project design in the sense they try to define project
work breakdown at
the same time as defining schedule activities. Messy and not
useful for large projects with many
activities; hard to display. Communicates little info per area
displayed. Only represent only part of cost,
time and scope of project. Do not represent size of project
relative to size of work elements. Magnitude
of behind-schedule condition easily miscommunicated. Fixed
height of bars, so they can misrepresent
time-phased workload. Two activities may appear to be same size,
but one can have 1 guy working on
it, the other a whole team.
7/28/2019 Csc 302 Notes
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Quality
value to someone, fitness to purpose, exceeding customer
expectations quality assurance focuses on V/V on quality of product
quality frameworks such as six sigma six sigma is not good for
software because: depends on human behavior, not predictable. can't
measure
degree of conformance. mapping between software faults and
failures is many to many. not all failures
result from the software itself. cannot accurately measure # of
faults in software
six sigma typical defect rate: would demand 0.0034 faults/KLOC
??Capability Maturity Model (CMM)
1. Initial: the starting point for use of a new or undocumented
repeat process2. Repeatable: the process is at least documented
sufficiently such that repeating the same steps may be
attempted
3. Defined: the process is defined/confirmed as a standard
business process, and decomposed to levels 0, 1and 2 (the last
being Work Instructions).
4. Managed: the process is quantitatively managed in accordance
with agreed-upon metrics.5. Optimizing: process management includes
deliberate process optimization/improvement.
Release Planning
What are we building? By when will it be ready? How many people
do we have? Big bang release: CD to store. Now things are done
continuously. Still need to plan though. Still need to
market things. Sales team needs to know when you will deliver so
they can sell it.
Essence of planning is uncertainty. Don't resist changes. If you
don't plan, move to CMM level 2. Why plan? external pressures. if
it was just for us (fun), not needed. With good data, good managers
make good decisions. Capacity vs. requirements. do we have the
capacity to fulfill all requirements? prioritized list of features?
For resources pick calendar days and determine work factors Put a
random bookmark at end of sprint. Quarterly release is an example
for sales/marketing. Requirements or Features (F): prioritized
potential requirements from wish list. planning poker estimation
Available resources (N): pick a value for T (workdays until
release/sprint/horizon) Capacity Constraint: F = N x T plan must
respect capacity constraint keep plan up to date with most current
estimates always dealing with overflow: move dates, cut features,
combination, adding developers is rarely helpful to plan
