Model-Based Design for Embedded Systems- P31: This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. | 266 Model-Based Design for Embedded Systems of decisions taken at a higher level of abstraction. Critical decisions instead involve the abstraction levels and semantics with which the functionality and the architecture are defined. Design Parameters for PBD In the PBD refinement-based design process platforms should be defined to eliminate large loop iterations for affordable designs. They should restrict the design space via new forms of regularity and structure that surrender some design potential for a lower cost and first-pass success. The library of functional and communication components is the design space that we are allowed to explore at the appropriate level of abstraction. Establishing the number location and components of intermediate platforms is an essential part of the PBD. Designs with different requirements and specifications may use different intermediate platforms hence different layers of regularity and designspace constraints. The trade-offs involved in the selection of the number and characteristics of platforms relate to the size of the design space to be explored and the accuracy of the estimation of the characteristics of the solution adopted. Naturally the larger the step across platforms the more difficult it is to predict the performance and provide tight bounds on the performance. In fact the design space for this approach may actually be smaller than the one obtained with smaller steps because it becomes more difficult to explore meaningful design alternatives and these restrictions on search impede design-space exploration. Ultimately predictions abstrac-tions may be so inaccurate that design optimizations are misguided and the bounds are incorrect leading to multiple design iterations. The identification of precisely defined layers where the mapping processes take place is an important design decision and should be agreed upon at the top design-management level. Each layer supports a design stage where the performance .
