Vendor Comments
Editor's Note: It is the policy of OR/MS Today to allow developers of software an opportunity to clarify and/or comment on the review article. Following are comments from Bob Whitehair, president of Probots, Inc.
We appreciate the thoughtful review of NETWK by Professor Donohue. With respect to potential improvements, on-line help and documentation are currently in progress. The node naming problem she encountered has been fixed and validation on node and group names has been improved. In addition, changes to existing group names automatically ripple through affected groups and constraints. One technical issue, due to documentation imprecision on our part, is that the proportionality relationship applies only to link groups in the current release; extension to node groups is straightforward and its absence has no affect on the generality of problems that can be formulated and solved. A significant use for this relation is in constructing variable proportion production functions.
A simple example of use of the required relation is the fixed cost investment decision; no output from a proposed new plant can flow to market unless the recovery of the total fixed cost of the plant leads to greater operational profitability. To represent this, create a link with its cost equal to the fixed cost; place each output link from the factory in a NETWK "Required" relation with the fixed cost link. This will force the fixed cost link to be used and its cost incurred before any product flows from the factory.
I will end by noting that the program scales to problems with thousands of variables. The use of metanodes, for example, allows representation of very complex networks that would be impossible to otherwise represent graphically in a Windows environment.
Product Information
NETWK is available from Probots, Inc., 189 Russell St., Hadley, MA 01035; phone: (413) 586-8929; fax: (413) 585-5707; E-mail: probots@wimsey.com.
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