Not so long ago, software used in distribution centers fit into a couple of neat categories. There was the warehouse management system (WMS), the market's dominant application, which essentially ran the DC operation, overseeing activities like receiving, putaway, and picking. Then there was the warehouse control system (WCS). Designed for distribution centers that utilized automated material handling equipment, the WCS primarily served as an interface between the WMS and the automated devices.

Technically a type of application known as "middleware," the WCS essentially functioned as an intermediary, passing along instructions from the central software system to conveyors, sorters, and the like. In the past, the "sole function [of the WCS] was to manage transactions as they occurred in real time on a conveyor line, in a sortation system, or in a storage system, while the WMS did its thing," said John M. Hill, a director at the consulting firm St. Onge. Hill made his remarks at a recent meeting of the Supply Chain Execution (SCE) Systems and Technology Group of the Material Handling Industry of America, during a discussion on the changing nature of WMS and WCS applications.

Today, some 35 companies—mostly systems integrators—provide WCS for this purpose, according to Hill. But in recent years, a number of WMS software developers have expanded beyond their traditional niche and begun offering both a WMS and a WCS. One such vendor is business software giant SAP, which offers both a WMS and a WCS (along with a host of other business applications). Others include the longtime WMS vendor RedPrairie as well as a relative newcomer to the marketplace, Reddwerks.

As the boundaries between WCS and WMS applications have blurred, some industry experts like Hill worry that DC managers are getting confused as to what's needed to make their operations run smoothly. They're not sure whether they need a WCS, a WMS, or a hybrid, he said at the SCE forum. "That disturbs me because this market is continuing to emerge, and we want sophisticated, well-informed customers making the right kinds of decisions for their operations."

In response to those concerns, another speaker at the forum noted that in at least one important way, the selection process hasn't changed much. The choice of software type still depends on what the company is doing in its warehouse, said James F. LeTart, director of marketing at RedPrairie. LeTart noted that almost every type of warehouse needs a WMS, but not every warehouse needs a WCS—only those with automated equipment.

Although he acknowledged that customers are driving a convergence between WMS and WCS, LeTart noted that the trend is still in its early stages and that the future of hybrid systems remains up in the air. "You don't go from being a WCS to being a full WMS," he said. "To say WCS is going to get there—well, maybe it will happen in time, but it certainly is not there today."

Given what's happening in the marketplace, logistics managers will likely have to study their options a bit more closely when they go to determine which type of software is right for their operations. Although buyers will still follow the same basic selection process, "their choices are that much more difficult because there is the overlap [between WCS and WMS]," said LeTart.