Central Interface Design Options

There are several design choices for the CI. The following is a description of these options along with the advantages and disadvantages of each one.

• The CI is responsible for any changes in the system and no other subsystem can perform any changes, but they can make suggestions to the CI. This means that the design subsystem is part of the CI. The advantages of this are:
  • More control on the design process.
  • No infinite cycles can happen.

  The disadvantages of this option are:

  • The user interface for the CI is more complicated.
  • More data should be kept in the global database, such as performance requirements, objective functions, etc.
  • A highly skilled user is required. This user should be able to perform both design and coordination at the same time.
  • An optimal design subsystem cannot be used in the system.
• The design subsystem gives initial values for some of the parameters and the CI supplies the rest of the parameters and also can override some of the parameters supplied by the optimal design subsystem. The advantages are:
  • Any optimization packedge can be used to obtain the initial values.
  • Some quick changes can be done from the CI directly.

  The disadvantages are:

  • The user interface for the CI is complicated.
  • Skilled users are required at both the design subsystem and the CI.
• No changes can be done by the CI, and the CI is only informed of any changes and reports them to the other subsystems. Also, the CI is responsible for checking the constraints and applying the update rules. The advantages are:
  • The user of the CI does not need to know much about the design details and technicalities.
  • Any design subsystem can be used by writing the required SSI for it and including it in the system.
  • The infinite design cycles are eliminated since the design constraints will be checked in the CI.

  The disadvantages are:

  • The CI has no control on the design parameters and any required changes should be done through one of the subsystems.
  • This scheme requires heavy use of interprocess communication which needs more sophisticated protocols to maintain reliable data transmission.

The last option has been chosen for our design. Thus, the CI will not change any of the parameters directly; however some of the parameters will be changed by the CI only when applying the update rules. For example, the link mass is calculated as the link length times the link cross-sectional area times the material density. So if any of the three parameters (length, area, density) is changed (usually by the design subsystem), then the mass will change by the corresponding update rule. The update rules should be cycle-free, i.e., any derived parameter must not change -- either directly or indirectly -- any of the parameters that are used in its calculations.