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"Freedom" Service-Oriented Methodology
Abstraction Levels

Overview  Process      Levels  Models  Definitions  Papers  Training

Unlike most software methodologies, which consist mainly of a process and associated rules or guidelines, Freedom is based on levels of abstraction for software methodologies as advocated by Dr. Charles McKay. A methodology constructed according to abstraction levels has at its foundation mathematically valid models, concepts, or principles. Higher-level abstractions are then based on, or derived from, this firm foundation. While the resulting methodology cannot, of course, be guaranteed to be perfect, the fact that it derives from a firm base bodes well for its ability to endure over time.

The Freedom methodology consists of six abstraction levels:

Level 6
Level 5
Level 4
Level 3
Level 2
Level 1

Level 1: Concept Models

Underlying the entire Freedom methodology is the concept that software may be viewed using box-structured models, as noted by Dr. Harlan Mills. Box-based models have been proven valid and effective in other engineering disciplines such as avionics, systems engineering, and electrical engineering. Freedom is founded on three box-structured concept models -- the black box model, gray box model, and white box model.

Level 2: Definitions

The concept model foundation offers a firm basis from which to derive definitions for key terminology. Freedom derives definitions for the key terms of requirements, design, and implementation from the models. This terminology serves to segregate software engineering information into three groups or categories.

Level 3: Principles

Principles are assertions regarding good software engineering practice that are backed by solid rationale. Definitions and principles guide creation of a robust rational process. The Freedom process is based on principles for build versus buy, requirements, object design, implementation and test, release, and evolution,

Level 4: Processes

With software system information categorized based on the definitions, processes for developing this information, and notations for recording it, are specified consistent with the stated principles. The definition-based information categorization determines precisely which information is within the scope of which processes.

Level 5: Products

Freedom applies different semantics to its process than other methodologies. Freedom's process charts do not specify rigorous steps that a developer must take when creating software. Rather, they follow the principle described in the 1986 Parnas paper "A Rational Design Process: How and Why To Fake It". This paper states that rational processes are impossible to follow rigorously, so do not try. Rather, developers should "fake" the process by producing the desired work products any way they can. The only caveat is the products delivered to the customer must be the same as would have been produced had the rational process been followed rigorously. When viewed from this perspective, processes do not exist to control people, but to more clearly define the nature of the work products to be produced.

Level 6: Tools

One of the most common mistakes made by developers of software engineering tools is developing such tools in isolation from a specific software development process or methodology. The result is tools that attempt to be process or methodology independent. While tools can be developed in this manner, in general they are not as powerful or high-leverage as tools targeted to a specific methodology. Thus, Freedom reserves the uppermost abstraction level for tools specific to Freedom's notations and processes. Sets of tools constructed in this way integrate well and are very high-leverage.

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