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Specification of Reactive Hardware/Software Systems - Electronic ...

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11.2 SHE Context and Phases 339<br />

11.2.4 Implementation<br />

Milestone 3 indicates the start <strong>of</strong> the actual implementation <strong>of</strong> a system. This implies<br />

detailed design <strong>of</strong> hardware and s<strong>of</strong>tware and possible other implementation technologies.<br />

The concrete activities in the implementation phase are for instance design on a<br />

Register Transfer Level (RTL) for hardware and programming in a language such as<br />

C++ for s<strong>of</strong>tware. In the future we foresee the automatic generation <strong>of</strong> for instance C++<br />

and VHDL.<br />

11.2.5 Overlap <strong>of</strong> <strong>Specification</strong> and Design<br />

Figure 11.4 shows the four phases and milestones again. This figure shows that our<br />

method aims at combining specification and design. On the right side we show the<br />

Preparation<br />

phase<br />

Modelling<br />

phase<br />

(SHE)<br />

Actual<br />

implementation<br />

phase<br />

Phase 1:<br />

Initial Requirements<br />

Description<br />

Milestone 1:<br />

Goal and purpose are formulated;<br />

Assignment for creation<br />

<strong>of</strong> Essential <strong>Specification</strong>.<br />

Phase 2:<br />

Essential <strong>Specification</strong><br />

Milestone 2:<br />

Conceptual solution implemented<br />

in Essential <strong>Specification</strong>;<br />

Assignment for Extended <strong>Specification</strong>.<br />

Phase 3:<br />

Extended <strong>Specification</strong><br />

Milestone 3:<br />

Extended <strong>Specification</strong> incorporates<br />

consequences <strong>of</strong> implementation technology<br />

Assignment for final design and implementation<br />

Phase 4:<br />

Implementation<br />

Figure 11.4: Overlap in <strong>Specification</strong> and Design<br />

<strong>Specification</strong><br />

Design<br />

overlap between specification and design. The specification <strong>of</strong> a system starts with a<br />

preparation phase (phase 1). The following phase is the SHE modelling phase which falls<br />

apart into two phases: Essential <strong>Specification</strong> phase (phase 2) and Extended <strong>Specification</strong><br />

phase (phase 3). Our method incorporates design activities on the appropriate levels <strong>of</strong><br />

abstraction. This means incorporation <strong>of</strong> high level architecture design in the Essential<br />

<strong>Specification</strong> phase, and incorporation <strong>of</strong> implementation technology decisions and<br />

their consequences for structure and behaviour in the Extended <strong>Specification</strong> phase.<br />

The extended modelling phase is a preparation for the actual implementation phase (phase<br />

4).

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