FOSD metamodels

<h2 id="metamodels">Metamodels</h2>
<p>A <a href="/facts/Metamodel/lA2nkA6J">metamodel</a> is a model whose instances are models.<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a> A <a href="/facts/Feature-oriented_programming/Ilc1y1nA">GenVoca</a> model of a product line is a tuple whose components are features (0-ary or 1-ary functions).  An extension (a.k.a. delta or refinement) of a model is a "meta-feature", which is a tuple of deltas that can modify an existing product line by modifying existing features and adding new features. As a simple example, consider GenVoca model M that contains three features a-c: 
</p>

M
        =
        [
        a
        ,
        b
        ,
        c
        ]
      
    
    {\displaystyle M=[a,b,c]}

<p>Suppose meta-model MM contains three meta-features AAA-CCC, each of which
is a tuple with a single non-identity feature:
</p>

M
                M
              
              
                
                =
                [
                A
                A
                A
                ,
                B
                B
                B
                ,
                C
                C
                C
                ]
              
            
            
              
              
                
                =
                [
                [
                a
                ,
                0
                ,
                0
                ]
                ,
                [
                0
                ,
                b
                ,
                0
                ]
                ,
                [
                0
                ,
                0
                ,
                c
                ]
                ]
              
            
          
        
      
    
    {\displaystyle {\begin{aligned}MM&=[AAA,BBB,CCC]\\&=[[a,0,0],[0,b,0],[0,0,c]]\end{aligned}}}

<p>where 0 is the null feature. Model M is constructed by adding the meta-features of MM, where + is the composition operation (see <a href="/facts/Feature-oriented_programming/Ilc1y1nA">FOSD</a>).
</p>

M
              
              
                
                =
                A
                A
                A
                +
                B
                B
                B
                +
                C
                C
                C
              
              
                
                  expression
                
              
            
            
              
              
                
                =
                [
                a
                ,
                0
                ,
                0
                ]
                +
                [
                0
                ,
                b
                ,
                0
                ]
                +
                [
                0
                ,
                0
                ,
                c
                ]
              
              
                
                  substitution
                
              
            
            
              
              
                
                =
                [
                a
                +
                0
                +
                0
                ,
                0
                +
                b
                +
                0
                ,
                0
                +
                0
                +
                c
                ]
              
              
                
                  composition
                
              
            
            
              
              
                
                =
                [
                a
                ,
                b
                ,
                c
                ]
              
              
                
                  simplification where 
                
                0
                +
                x
                =
                x
                +
                0
                =
                x
              
            
          
        
      
    
    {\displaystyle {\begin{aligned}M&=AAA+BBB+CCC&{\text{expression}}\\&=[a,0,0]+[0,b,0]+[0,0,c]&{\text{substitution}}\\&=[a+0+0,0+b+0,0+0+c]&{\text{composition}}\\&=[a,b,c]&{\text{simplification where }}0+x=x+0=x\end{aligned}}}

<p>MM models a product line of product lines (PL**2). That is, different MM expressions correspond to GenVoca models of different product lines..
</p>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Feature-oriented_programming/Ilc1y1nA">Feature-oriented programming</a> – basic overview</li>
<li><a href="/facts/FOSD_origami/D3pIk68V">FOSD origami</a></li>
<li><a href="/facts/FOSD_program_cubes/4ag1SC5d">FOSD program cubes</a> – multi-dimensional product lines</li>
<li>FOSD feature interactions – other operations on features, including an operation designating feature interaction</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>"Scaling Step-Wise Refinement" (PDF). <a href="ftp://ftp.cs.utexas.edu/pub/predator/TSE-AHEAD.pdf" target="_blank">ftp://ftp.cs.utexas.edu/pub/predator/TSE-AHEAD.pdf</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
</ol>

FOSD metamodels open-in-new

FOSD metamodels