COTS-Based Systems (CBS) Functional Density—A Heuristic for Better CBS Design

Abstract

Abstract. The conventional rationale for using COTS (commercial offthe-shelf) components is that the more a software system is built from COTS products, the lower the cost of initial development. Less understood is that during the long term sustainment phase -from deployment through retirement -the cost of maintenance of a COTS-based system generally increases as the number of COTS products used increases. There exists then a tension between the imperative to maximize the use of COTS components to ease CBS development yet minimize the use of COTS components to ease CBS maintenance. A heuristic called the "CBS Functional Density Rule" is proposed to reconcile these two conflicting views. A corresponding metric for characterizing the "efficiency" of a given CBS design relative to another called the "COTS Functional Density" is then suggested. The paper concludes with suggestions for additional research to further validate the empirical foundations of the proposed heuristic and associated metric.

Early detection of COTS component functional suitability

“…In this proposal, the number of components in the solution should be minimized and the contribution of functionality should be maximized to satisfy the CBS Functional Density Rule of Thumb: ''Maximize the amount of functionality in your system provided by COTS components but using as few COTS components as possible'' [5]. However, there is no further detail on what ''amount of functionality'' is.…”

“…Finally, our measures on functional suitability might provide a more precise indicator when calculating the maintenance equilibrium value as introduced by Abts in [5]. In this proposal, the number of components in the solution should be minimized and the contribution of functionality should be maximized to satisfy the CBS Functional Density Rule of Thumb: ''Maximize the amount of functionality in your system provided by COTS components but using as few COTS components as possible'' [5].…”

“…We only have to look at our case study and the componentSource catalogue again 5 . From there and browsing the Web, we realized that the Bahs Software company is not a component supplier any more, and consequently AcceptOnline, CCProcessing, (6) Classification is not straightforward.…”

“…Then, we mirror some efforts in literature [5][6][7], meaning that functionality is our main concern, but addressing how functional suitability might be quantified at early stages of the selection process. Differently from those proposals, our metrics [8] are defined considering that only a high-level description of the COTS components is available, without further details on data and control execution.…”

A decision making model for software design

“…COTS-based Integrated System Development (CISD) [5] consists of three phases: identification, evaluation and integration. Identification includes collecting and understanding system requirements and identifying and classifying COTS software products.…”