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<a name="definition"><h2>Definition</h2></a>
<p class="Para">A viewpoint is a software perspective with all the conventions for constructing and using it.</p>
<a name="motivation"><h2>Motivation</h2></a>
<p class="Para">The notion of viewpoint is introduced to decouple the generation concerns from the logic of generation itself realized by a activities (factory components, tasks). For instance, instead of declaring a mapping in code, it is explicitly declared in a mapping viewpoint with a mapping model. A generation can use several complementary viewpoints. Conversely, all the complementary viewpoints must cover all the generation concerns.</p>
<p class="Para">Examples of viewpoints:</p>
<ul CLASS="UnorderedList">
<li CLASS="Item">Model to model mapping (e.g., eCore-to-ecore, ecore-to-UML mappings)</li>
<li CLASS="Item">Generation with patterns</li>
<li CLASS="Item">DSL (Domain-Specific Language)</li>
<li CLASS="Item">Functional description</li>
<li CLASS="Item">Non-functional description (e.g., performance, safety, security)</li>
<li CLASS="Item">Architecture decisions</li>
<li CLASS="Item">Software product line decisions</li>
<li CLASS="Item">Deployment</li>
<li CLASS="Item">Licensing</li>
<p class="Para">The structure of a specific viewpoint is presented in its own section. This section develops the generic concept of viewpoint and its relationship with the IEEE 1471-2000 <a href="#[1]">[1]</a> and ISO/IEC WD3 42010 - IEEE P42010/D3 <a href="#[2]">[2]</a> standards. The purpose of a viewpoint is to explicitly describe generation specifications and decisions. A viewpoint actually translates a generation concern and helps a software actor to express or understand a part of the generation description, and this without being polluted by implementation details. Regarding the software architecture description, generation description by viewpoint becomes a sub-part of the software architecture description.</p>
<a name="structure"><h2>Structure</h2></a>
<p class="Para">A viewpoint implements a software perspective with its own rationale, i.e. a purpose, choices and decisions, and practices. Several viewpoints can mutually implement the same perspective. For instance, the generation of a tool infrastructure requires mapping, non-functional (e.g., persistence), deployment viewpoints. A viewpoint is instatiated and stored in a model. The metamodel of this model formalizes a language, typically expressed with a DSL. Then, all the viewpoints jointly formalized the software architecture from the generation consideration.</p>
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<img src="./images/viewpointStructure.jpg" alt="Viewpoint structure"/>
<p align="center">
<i>Figure 1. Viewpoint Structure</i>
<a name="Extensibility"><h2>Extensibility</h2></a>
<p>The list of viewpoints is variable with the project concerns. This implies that the structure where the viewpoints are described must be extensible and to meet evolution of generation needs.</p>
<dt><a name="[1]">[1]</a> IEEE Standard 1471-2000, <i>IEEE Recommended Practice for Architectural Description of Software-Intensive Systems</i>, 21 September, 2000.</dt>
<dt><a name="[2]">[2]</a> ISO/IEC WD3 42010, IEEE P42010/D3, <i>Systems and software engineering - Architectural description</i>, 2008-09-14.</dt>