Chapter 2 Flashcards
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1
Q
Software Process Definition
A
A structured set of activities required to develop a software system.
2
Q
Software Process Model Definition
A
- An abstract representation of a process
- Presents a description of a process from some particular perspective.
3
Q
Many different software processes all involve ________
A
- Specification
- Design and implementation
- Validation
- Evolution
4
Q
Different Software Processes Involve:
Specification
A
Defining what the system should do
5
Q
Different Software Processes Involve:
Design and Implementation
A
Defining the organization of the system and implementing the system;
6
Q
Different Software Processes Involve:
Validation
A
Checking that it does what the customer wants
7
Q
Different Software Processes Involve
Evolution
A
Changing the system in response to changing customer needs
8
Q
Software Process Descriptions may include ______
A
- Products
- Roles
- Pre- and post-conditions
9
Q
Software Process Descriptions Include:
Products
A
outcomes of a process activity
10
Q
Software Process Descriptions Include:
Roles
A
reflect the responsibilities of people involved in the process
11
Q
Software Process Descriptions Include:
Pre and Post Conditions
A
statements that are true before and after a process activity has been enacted or a product produced.
12
Q
Plan-Driven Processes
A
Processes where all of the process activities are planned in advance and progress is measured against this plan.
13
Q
Agile Processes
A
Planning is incremental and it is easier to change the process to reflect changing customer requirements.
14
Q
In practice, most practical processes include elements of both plan-driven and agile approaches.
A
There are no right or wrong software processes.
15
Q
Types of software process models
A
- Waterfall model
- Incremental development
- Integration and configuration
16
Q
Software Process Models
Waterfall Model
A
Plan-driven model. Separate and distinct phases of specification and development.
17
Q
Software Process Models
Incremental Development
A
Specification, development and validation are interleaved. May be plan-driven or agile.
18
Q
Software Process Models
Integration and Configuration
A
The system is assembled from existing configurable components. May be plan-driven or agile.
19
Q
Waterfall Model Phases
A
- Requirements analysis and definition
- System and software design
- Implementation and unit testing
- Integration and system testing
- Operation and maintenance
20
Q
Waterfall Model Main Drawback
A
- Difficulty of accommodating change after the process is underway.
- In principle, a phase has to be complete before moving onto the next phase.
21
Q
Waterfall model problems
A
- Inflexible partitioning of the project into distinct stages makes it difficult to respond to changing customer requirements.
- Only appropriate when the requirements are well-understood and changes will be fairly limited during the design process.
The waterfall model is mostly used for large systems engineering projects where a system is developed at several sites.
* The plan-driven nature of the waterfall model helps coordinate the work.
22
Q
Incremental Development Benefits
A
- The cost of accommodating changing customer requirements is reduced.
- The amount of analysis and documentation that has to be redone is much less than is required with the waterfall model.
- It is easier to get customer feedback on the development work that has been done. Customers can comment on demonstrations of the software and see how much has been implemented.
- More rapid delivery and deployment of useful software to the customer is possible. Customers are able to use and gain value from the software earlier than is possible with a waterfall process.
23
Q
Incremental development problems
A
- The process is not visible.
- Managers need regular deliverables to measure progress. If systems are developed quickly, it is not cost-effective to produce documents that reflect every version of the system.
System structure tends to degrade as new increments are added.
- Unless time and money is spent on refactoring to improve the software, regular change tends to corrupt its structure.
- Incorporating further software changes becomes increasingly difficult and costly.
24
Q
Types of reusable software
A
- Stand-alone application systems (sometimes called COTS) that are configured for use in a particular environment. (Commercial-Off-the-Shelf)
- Collections of objects that are developed as a package to be integrated with a component framework such as .NET or J2EE.
- Web services that are developed according to service standards and which are available for remote invocation.
25
Reuse-oriented software engineering key process stages
* Requirements specification
* Software discovery and evaluation
* Requirements refinement
* Application system configuration
* Component adaptation and integration
26
Advantages and disadvantages of Reuse-oriented software
* Reduced costs and risks as less software is developed from scratch
* Faster delivery and deployment of system
* But requirements compromises are inevitable so system may not meet real needs of users
* Loss of control over evolution of reused system elements
27
Process Activities Definition
* Real software processes are inter-leaved sequences of technical, collaborative and managerial activities with the overall goal of specifying, designing, implementing and testing a software system.
* The four basic process activities of specification, development, validation and evolution are organized differently in different development processes.
* For example, in the waterfall model, they are organized in sequence, whereas in incremental development they are interleaved.
28
Requirements engineering process
- Requirements elicitation and analysis
*What do the system stakeholders require or expect from the system?*
- Requirements specification
*Defining the requirements in detail*
- Requirements validation
*Checking the validity of the requirements*
29
Software design and implementation Definition
The process of converting the system specification into an executable system.
Software design
* Design a software structure that realizes the specification;
Implementation
* Translate this structure into an executable program;
The activities of design and implementation are closely related and may be inter-leaved.
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Design activities
* Architectural design
* Database design
* Interface design
* Component selection and design
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# Design Activities
Architectural Design
where you identify the overall structure of the system, the principal components (subsystems or modules), their relationships and how they are distributed.
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# Design Activities
Database Design
where you design the system data structures and how these are to be represented in a database.
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# Design Activities
Interface Design
where you define the interfaces between system components.
34
# Design Activities
Component Selection and Design
where you search for reusable components. If unavailable, you design how it will operate.
35
System Implementation Definition
* The software is implemented either by developing a program or programs or by configuring an application system.
* **Design and implementation** are interleaved activities for most types of software system.
* **Programming** is an individual activity with no standard process.
* **Debugging** is the activity of finding program faults and correcting these faults.
36
Software Validation Definition
* **Verification and validation (V & V)** is intended to show that a system conforms to its specification and meets the requirements of the system customer.
* Involves checking and review processes and system testing.
* **System testing** involves executing the system with **test cases** that are derived from the specification of the real data to be processed by the system.
* ***Testing*** is the most commonly used V & V activity.
37
Stages of Testing
* Component testing
* System testing
* Customer testing
38
# Stages of Testing
Component Testing
* Individual components are tested independently;
* Components may be functions or objects or coherent groupings of these entities.
39
# Stages of Testing
System Testing
Testing of the system as a whole. Testing of emergent properties is particularly important.
40
# Stages of Testing
Customer Testing
Testing with customer data to check that the system meets the customer’s needs.
41
Software Evolution Definition
* Software is inherently flexible and can change.
* As requirements change through changing business circumstances, the software that supports the business must also evolve and change.
* Although there has been a demarcation between development and evolution (maintenance) this is increasingly irrelevant as fewer and fewer systems are completely new.
42
Coping with Change
Change is **inevitable** in all large software projects.
* Business changes lead to new and changed system requirements
* New technologies open up new possibilities for improving implementations
* Changing platforms require application changes
Change leads to **rework ** so the costs of change include both rework (e.g. re-analyzing requirements) as well as the costs of implementing new functionality.
43
Reducing the costs of rework
* **Change anticipation**, where the software process includes activities that can anticipate possible changes before significant rework is required.
* For example, a prototype system may be developed to show some key features of the system to customers.
* **Change tolerance**, where the process is designed so that changes can be accommodated at relatively low cost.
44
# Reducing the costs of rework
where the software process includes activities that can anticipate possible changes before significant rework is required.
Change Anticipation
45
# Reducing the costs of rework
where the process is designed so that changes can be accommodated at relatively low cost.
Change Tolerance
46
Coping with changing requirements
* **System prototyping**, where a version of the system or part of the system is developed quickly to check the customer’s requirements and the feasibility of design decisions. This approach **supports change anticipation.**
* **Incremental delivery**, where system increments are delivered to the customer for comment and experimentation. This **supports both change avoidance and change tolerance.**
47
# Coping with changing requirements
( -------- ) , where a version of the system or part of the system is developed quickly to check the customer’s requirements and the feasibility of design decisions. This approach supports ( -------- ).
* System Protoyping
* Change Anticipation
48
( --------- ), where system increments are delivered to the customer for comment and experimentation. This supports (---------).
* Incremental Delivery
* both change avoidance and change tolerance
49
Software Prototype Definition
A prototype is an **initial version** of a system used to demonstrate concepts and try out design options.
50
A prototype can be used in:
* The **requirements engineering process** to help with requirements elicitation and validation;
* In **design processes** to explore options and develop a UI design;
* In the **testing process** to run back-to-back tests.
51
Benefits of prototyping
* Improved system usability. A closer match to users’ real needs.
* Improved design quality.
* Improved maintainability.
* Reduced development effort.
52
Prototype development
* May be based on rapid prototyping languages or tools
* May involve leaving out functionality:
* Prototype should focus on areas of the product that are **not well-understood**;
* **Error checking and recovery** may **not be included ** in the prototype;
* Focus on **functional** rather than non-functional requirements such as reliability and security.
53
Throw-away prototypes
* Prototypes should be discarded after development as they are not a good basis for a production system:
* It may be impossible to tune the system to meet non-functional requirements;
* Prototypes are normally undocumented;
* The prototype structure is usually degraded through rapid change;
* The prototype probably will not meet normal organizational quality standards.
54
Incremental Delivery Definition
* Rather than deliver the system as a single delivery, the development and delivery is broken down into increments with **each increment delivering part of the required functionality**.
* **User requirements are prioritized** and the highest priority requirements are included in early increments.
* Once the development of an increment is started, the requirements are frozen though requirements for later increments can continue to evolve.
55
Incremental delivery
* Deploy an increment for use by end-users;
* More realistic evaluation about practical use of software;
* Difficult to implement for replacement systems as increments have less functionality than the system being replaced.
56
Incremental development
* Develop the system in increments and evaluate each increment before proceeding to the development of the next increment;
* Normal approach used in agile methods;
* Evaluation done by user/customer proxy.
57
Incremental delivery advantages
* Customer value can be delivered with each increment so system functionality is available earlier.
* Early increments act as a prototype to help elicit requirements for later increments.
* Lower risk of overall project failure.
* The highest priority system services tend to receive the most testing.
58
Incremental delivery problem 1
Most systems require a set of basic facilities that are used by different parts of the system.
* As requirements are not defined in detail until an increment is to be implemented, it can be **hard to identify common facilities** that are needed by all increments.
59
Incremental delivery problem 2
The essence of iterative processes is that the specification is developed in conjunction with the software.
* However, this conflicts with the procurement model of many organizations, where the complete system specification is part of the system development contract.
60
Process Improvement Definition
* Many software companies have turned to software process improvement as a way of enhancing the quality of their software, reducing costs or accelerating their development processes.
* **Process improvement** means understanding existing processes and changing these processes to increase product quality and/or reduce costs and development time.
61
# Approaches to Improvement
* The (--------), which focuses on improving process and project management and introducing good software engineering practice.
process maturity approach
## Footnote
The level of process maturity reflects the extent to which good technical and management practice has been adopted in organizational software development processes.
62
# Approaches to improvement
* The (--------), which focuses on iterative development and the reduction of overheads in the software process.
**agile approach**
## Footnote
The primary characteristics of agile methods are rapid delivery of functionality and responsiveness to changing customer requirements.
63
The process improvement Cycle
Measure
Analyze
Change
64
# Process Improvement Activities
Process measurement
You measure one or more attributes of the software process or product. These measurements forms a baseline that helps you decide if process improvements have been effective.
65
# Process Improvement Activities
Process analysis
The current process is assessed, and process weaknesses and bottlenecks are identified. **Process models** (sometimes called process maps) that describe the process may be developed.
66
# Process Improvement Activities
Process change
Process changes are proposed to address some of the identified process weaknesses. These are introduced and the cycle resumes to collect data about the effectiveness of the changes.
67
Process metrics
* Time taken for process activities to be completed
E.g. Calendar time or effort to complete an activity or process.
* Resources required for processes or activities
E.g. Total effort in person-days.
* Number of occurrences of a particular event
E.g. Number of defects discovered.
68
Capability maturity levels
Level 1: Initial
Level 2: Managed
Level 3: Defined
Level 4: Quantitatively Managed
Level 5: Optimizing
69
# SEI Capability maturity levels
Initial
Essentially uncontrolled
70
# SEI Capability maturity levels
Repeatable
Product management procedures defined and used
71
# SEI Capability maturity levels
Defined
Process management procedures and strategies defined and used
72
# SEI Capability maturity levels
Managed
Quality management strategies defined and used
73
# SEI Capability maturity levels
Optimizing
Process improvement strategies defined and used
