  The paper addresses aggregation issues for composite (modular) solutions. A
systemic view point is suggested for various aggregation problems. Several
solution structures are considered: sets, set morphologies, trees, etc. Mainly,
the aggregation approach is targeted to set morphologies. The aggregation
problems are based on basic structures as substructure, superstructure,
median/consensus, and extended median/consensus. In the last case, preliminary
structure is built (e.g., substructure, median/consensus) and addition of
solution elements is considered while taking into account profit of the
additional elements and total resource constraint. Four aggregation strategies
are examined: (i) extension strategy (designing a substructure of initial
solutions as "system kernel" and extension of the substructure by additional
elements); (ii) compression strategy (designing a superstructure of initial
solutions and deletion of some its elements); (iii) combined strategy; and (iv)
new design strategy to build a new solution over an extended domain of solution
elements. Numerical real-world examples (e.g., telemetry system, communication
protocol, student plan, security system, Web-based information system,
investment, educational courses) illustrate the suggested aggregation approach.
