Lecture 8: Change Management Flashcards
Why Change Management?
The problem:
- Multiple people work on artifacts that are changing
- More than one version of the artifact has to be supported:
- Released software systems
- Custom configured systems (different functionality)
- Systems under development
- Software running on different machines & operating systems
- ➭Need for coordination
- Software Configuration Management
- manages evolving software systems
- controls the costs involved in making changes to a system.
What is Software Configuration Management?
- Definition Software Configuration Management:
- A set of management disciplines within a software engineering process to develop a baseline*
- Software Configuration Management encompasses the disciplines and techniques of initiating, evaluating and controlling change to work products during and after a software project
- Standard:
- IEEE 828-2012: IEEE Standard for Configuration
- Management in Systems and Software Engineering.
Administering Software Configuration Management
- Software Configuration Management is a project function with the goal to make technical and managerial activities more effective
- Software Configuration Management can be administered in several ways:
- • Organization-wide
- • Project-specific
- • Distributed among the project members
- • Mixture of all of the above.
Configuration Management Roles
- Configuration Manager
- Responsible for identifying configuration items
- Also often 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.
Configuration Management Activities
- Configuration item identification
- Modeling the system as a set of evolving components
- Promotion management
- The creation of versions for other developers
- Release management
- The creation of versions for clients and users
- Change management
- The handling, approval & tracking of change requests
- Branch management
- The management of concurrent development
- Variant management
- The management of coexisting versions
Configuration Item
Configuration Item: An aggregation of software, hardware, or both, designated for configuration management and treated as a single entity in the configuration management process.
- Software configuration items: source files, models, tests, binaries, documents, configurations
- Hardware configuration items: e.g. CPUs, bus speed frequencies, sensors, actuators
Configuration Item Identification
- Not every entity needs to be under configuration management control all the time
- Two Issues:
- What: Selection of Configuration Items
- What should be under configuration control?
- What: Selection of Configuration Items
- When: When do you start to place entities under
- configuration control?
- • In early days, it was an activity
- • Nowadays it should be a project function (from beginning to end of the project)
Configuration Item Identification
- Selecting the right configuration items is a skill that takes practice
- Very similar to object modeling
- Use techniques similar to object modeling for findingvconfiguration items:
- Identify the configuration items
- Findrelationshipsbetweentheconfigurationitems.
Terminology: Version
Version: The initial release or re-release of a configuration item associated with a complete compilation or recompilation of the item. Different versions have different functionality.
Terminology: SCM Directories
- Programmer’s Directory (IEEE 1042: Dynamic Library)
- • Library for holding newly created or modified software entities
- • The programmer’s workspace is controlled by the programmer only
- Master Directory (IEEE 1042: Controlled Library)
- • Manages the current baseline(s) and for controlling
- changes made to them
- • Changes must be authorized
- Software Repository (IEEE 1042: Static Library)
- • Archive for the various baselines released for general use
- • Copies of these baselines may be made available to requesting organizations.
Promotion and Release Management
- • Promotion: The internal development state of a software is changed
- • Release: A changed software system is made visible outside the development organization
Terminology: Version vs. Revision
- Release: The formal distribution of an approved version
- 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.
Terminology: Baseline
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 changed only be through formal change control procedures.
• Examples:
- • Baseline A: The API has been completely been defined;
- the bodies of the methods are empty
- • Baseline B: All data access methods are implemented and tested
- • Baseline C: The GUI is implemented.
Types of Baselines
As systems are developed, a series of baselines is developed, usually after a review (analysis review, design review, code review, system testing, …)
- • Developmental baseline
- • Functional baseline
- • Product baseline
Branch Management allows to transition between these baselines
Branch Management Model
- Example of a Branching Model (e.g. in Git)
- Master Branch: External Release (e.g. Product Increment)
- Development Branch: Internal Release
- Feature Branches: Incremental development and explorations
Architectural Styles for Version Control
- Monolithic (Standalone)
- Repository Style (Client-Server)
• Peer-to-peer
Monolithic Architecture for Version Control
Programmer has a simple local database that keeps all the changes to files under revision control.
Example of Monolithic Version Control Architecture: RCS. Still distributed with many computers today.
Repository Architecture for Version Control
A single server contains all the versioned files
Programmers check out files from to the server to their computer, change them and check them back into the server
Administrators have fine-grained control over who can do what
Problem:
• Single point of failure in the Central VCS Server: Possibility of loosing all the versions and their history if the server crashes.
Peer-to-Peer Architecture for Version Control
Addresses the single point of failure problem
Each programmer’s directory (Computer A, Computer B,…) fully mirrors the master directory (Server Computer)
Programmers can work offline on their own branches
If the server dies and a programmer has a full copy of the master directory, it can be copied back to the Server computer
Example: Git.
Change management
- Change management is the handling of change requests
- The general change management process:
- The change is requested
- The change request is assessed against requirements and
- project constraints
- Following the assessment, the change request is accepted or rejected
- If it is accepted, the change is assigned to a developer and implemented
- The implemented change is audited.
Change Policies
- The purpose of a change policy is to guarantee that each promotion or release conforms to commonly accepted criteria
- Examples for change policies:
- “No developer is allowed to promote source code which was compiled with errors or warnings.”
- “No baseline can be released without having been beta- tested by at least 500 external persons.”
Change Management Activities and Responsibilities
- Configuration Control: Managing a Change Request
- Configuration Status Accounting
- Configuration Audits and Reviews
- Interface Control
Configuration Control
- Define a change request form
- Define management procedures for:
- • Identification of the need for a change request
- • Analysis and evaluation of a change request
- • Approval or disapproval of a change request
- • Implementation, verification and release of the change
Configuration Status Accounting
Answers the following questions:
- What elements are to be tracked and reported for
- baselines and changes?
- What types of status accounting reports are to be generated? What is their frequency?
- How is information to be collected, stored and reported?
- How is access to the configuration management status data controlled?
