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diff --git a/more/feature_model_diagrams.htm b/more/feature_model_diagrams.htm new file mode 100644 index 0000000000..2ca017a933 --- /dev/null +++ b/more/feature_model_diagrams.htm @@ -0,0 +1,112 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> +<html> + +<head> +<meta http-equiv="Content-Type" content="text/html; charset=windows-1252"> +<meta name="GENERATOR" content="Microsoft FrontPage 5.0"> +<meta name="ProgId" content="FrontPage.Editor.Document"> +<title>Feature Model Diagrams</title> +</head> + +<body bgcolor="#FFFFFF" text="#000000"> + +<p><img border="0" src="../boost.png" alt="Boost logo" width="277" height="86"></p> +<h1>Feature Model Diagrams in text and HTML</h1> +<p>By <a href="../people/beman_dawes.html">Beman Dawes</a></p> +<h2>Introduction</h2> +<p>In their seminal book, Generative Programming, Czarnecki and Eisenecker (<a href="#Generative%20Programming">C&E</a>)) +describe how to build feature models [C&E 4.4] consisting of a feature +diagram plus semantic, rationale, and other attributes. Feature models are +then used to drive design cycles which eventually lead to manual or automatic +assembly of configurations.</p> +<p>Feature models provide a language to describe the library variability that is +often such an issue in boost.org discussions. The Whorf hypothesis that +"Language shapes the way we think, and determines what we can think +about" seems to apply. In discussion of library variability issues, +we have been crippled by lack of a good language. With feature models we now +have a language to carry on the dialog.</p> +<p>The graphical feature diagrams presented by C&E are not in a suitable +form for the email discussions boost.org depends upon. The hierarchical nature +of feature diagrams can be represented by a simple text-based feature diagram +language. A feature model can also take advantage of the hyperlinks +inherent in HTML.</p> +<h2><a name="Grammar">Grammar</a></h2> +<p>The grammar for the feature diagram language is expressed in Extended +Bakus-Naur Form; ::= represents productions, [...] represents options, {...} +represents zero or more instances, and represents | alternatives.</p> +<blockquote> + <pre>feature-model ::= concept-name details { feature }</pre> + <pre>feature ::= feature-name [details]</pre> + <pre>details ::= "(" feature-list ")" // required features + | "[" feature-list "]" // optional features</pre> + <pre>feature-list ::= element { "|" element } // one only + | element { "+" element } // one or more + | element { "," element } // all + // [a+b] equivalent to [a,b]</pre> + <pre>element ::= feature + | details</pre> + <pre>concept-name ::= name</pre> + <pre>feature-name ::= name</pre> +</blockquote> +<p>The usual lexical conventions apply. Names are case-insensitive and consist +of a leading letter, followed by letters, digits, underscores or hyphens, with +no spaces allowed.</p> +<p>At least one instance of each name should be hyperlinked to the corresponding +<a href="#FeatureDescriptions">Feature Description</a>.</p> +<p>While the grammar is intended for written communication between people, it +may also be trivially machine parsed for use by automatic tools.</p> +<h2><a id="FeatureDescriptions" name="FeatureDescriptions"></a></h2> +<p>Descriptive information is associated with each concept or feature. According +to [C&E 4.4.2] this includes:</p> +<ul> + <li>Semantic descriptions.</li> + <li>Rationale.</li> + <li>Stakeholders and client programs.</li> + <li>Exemplar systems.</li> + <li>Constraints and default dependency rules.</li> + <li>Availability sites, binding sites, and binding mode.</li> + <li>Open/Closed attribute.</li> +</ul> +<h2>What is a Feature?</h2> +<p>A feature [C&E 4.9.1] is "anything users or client programs might +want to control about a concept. Thus, during feature modeling, we +document no only functional features ... but also implementation features, ..., +various optimizations, alternative implementation techniques, and so on."</p> +<h2>Example</h2> +<blockquote> + <pre>special-container ( organization, + performance, + interface ) // all required</pre> + <pre>organization [ ordered + indexed ] // zero or more (4 configurations)</pre> + <pre>indexed [ hash-function ] // zero or one (2 configurations)</pre> + <pre>performance ( fast | small | balanced ) // exactly one (3 configurations)</pre> + <pre>interface ( STL-style + cursor-style ) // one or more (3 configurations)</pre> +</blockquote> +<p>There should be feature descriptions for <code>some-container, organization, +ordered, indexed, hash-function, performance, fast, small, balanced, interface, +STL-style, and cursor-style</code>.</p> +<p>The number of possible configurations is (2 + 2*2) * 3 * 3 = 54, +assuming no constraints.</p> +<p>There are equivalent representations. For example:</p> +<blockquote> + <pre>special-container ( organization[ ordered+indexed[ hash-function ]], + performance( fast|small|balanced ), + interface( STL-style+cursor-style ) )</pre> +</blockquote> +<h2>References</h2> +<p>Krzysztof Czarnecki and Ulrich W. Eisenecker, <a href="http://www.generative-programming.org">Generative +Programming</a>, Addison-Wesley, 2000, ISBN 0-201-30977-7</p> +<hr> +<p>Revised <!--webbot bot="Timestamp" s-type="EDITED" s-format="%d %B %Y" startspan -->26 August 2004<!--webbot bot="Timestamp" endspan i-checksum="32277" --></p> +<p>© Copyright Beman Dawes, 2000</p> + +<p> + Distributed under the Boost Software License, Version 1.0. (See + accompanying file <a href="../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or copy + at <a href= + "http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>) +</p> + +</body> + +</html> |