Baseline (configuration management)
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Configuration management is the process of managing change in hardware, software, firmware, documentation, measurements, etc. As change requires an initial state and next state, the marking of significant states within a series of several changes becomes important. The identification of significant states within the revision history of a configuration item is the central purpose of baseline identification.
Typically, significant states are those that receive a formal approval status, either explicitly or implicitly (approval statuses may be marked individually, when such a marking has been defined, or signified merely by association to a certain baseline). Nevertheless, this approval status is usually recognized publicly. Thus, a baseline may also mark an approved configuration item, e.g. a project plan that has been signed off for execution. In a similar manner, associating multiple configuration items with such a baseline indicates those items as being approved.
- Generally, a baseline may be a single work product, or set of work products that can be used as a logical basis for comparison. A baseline may also be established (whose work products meet certain criteria) as the basis for subsequent select activities. Such activities may be attributed with formal approval.
Conversely, the configuration of a project often includes one or more baselines, the status of the configuration, and any metrics collected. The current configuration refers to the current status, current audit, current metrics, and latest revision of all configuration items. Similarly, but less frequently, a baseline may refer to all items associated with a specific project. This may include all revisions of all items, or only the latest revision of all items in the project, depending upon context, e.g. "the baseline of the project is proceeding as planned."
A baseline may be specialized as a specific type of baseline. Some examples include:
- Functional Baseline: initial specifications established; contract, etc.
- Allocated Baseline: state of work products once requirements are approved
- Developmental Baseline: state of work products amid development
- Product Baseline: contains the releasable contents of the project
- others, based upon proprietary business practices
Capabilities of Baselines 
While marking approval status covers the majority of uses for a baseline, baselines may also be established merely to signify the progress of work through the passage of time. In this case, a baseline is a visible stake through an endured collective effort, e.g. a developmental baseline. Baselines may also mark milestones; albeit some milestones also signify approval.
Baselines themselves are valued not only for their ability to identify the notable state of work product(s) but also provide particular importance in their ability to be retrieved. Once retrieved, the state of the work product(s) in that subset share the same significance in their history of changes that this significance was observed. The baseline is then regarded with poignant qualities (either favorably or disfavorably). For this reason, baseline identification, monitoring, and retrieval are critical to the success of configuration management. However, the ease of retrieving any given baseline varies according to the system employed for performing configuration management which may use a manual, automated, or hybrid approach. Once retrieved, the baseline may be compared to a particular configuration or another baseline.
Most baselines are established at a fixed point in time and serve to continue to reference that point (identification of state). However, some baselines are established to carry forward as a reference to the item itself regardless of any changes to the item. These latter baselines evolve with the progression of the work effort but continue to identify notable work products in the project.
Baselining Configuration Items 
In the process of performing configuration management, configuration items (or work products) may be baselined so as to establish them with a certain status to interested parties. In this sense, to baseline a work product may require certain change(s) to the work product to ensure its conformance to the characteristics associated with the baseline referenced. This varies upon context, but in many cases this has the implication that the work product is "reset" to an initial (possibly inherently approved) state from which work may proceed.
Baseline Control 
In many environments, baselines are controlled such that certain subsequent activities against work products in that baseline are either prohibited or permitted. These activities are carefully selected and controlled, and again, depending upon the configuration management system, are also monitored. Consequently, baselines are ordinarily subjected to configuration management audits. Configuration Audits may include an examination of specific actions performed against the baseline, identification of individuals involved in any action, an evaluation of change within the baseline, (re-)certification for approval, accounting, metric collection, comparison to another baseline, or all of these.
Though common in software revision control systems as labels or tags, the existence of baselines is found in several other technology-related domains. Baselines can be found in UML modeling systems and business rule management systems, among others.
In addition to the field of hardware and software engineering, baselines can be found in medicine (e.g. monitoring health progress), politics (e.g. statistics), physics and chemistry (e.g. observations and changes), finance (e.g. budgeting), and others.
See also 
- CMMI Product Team, "Chpt 7, Maturity Level 2: Managed, Configuration Management, SP 1.3," in Capability Maturity Model Integration, Version 1.1 (CMMI-SE/SW/IPPD/SS, V1.1): Staged Representation, Carnegie Mellon Software Engineering Institute.
- IEEE Computer Society, "Chpt 7, 2.1.5. Baseline," in Guide to the Software Engineering Body of Knowledge, 2004 Version, Edited by Deborah Plummer. IEEE Computer Society Press, 2005. ISBN 0-7695-2330-7