In her book "Electronic Performance Support Systems" published in 1991, Gloria Gery, defined EPSS as

"an integrated electronic environment that is available to and easily accessible by each employee and is structured to provide immediate, individualized on-line access to the full range of information, software, guidance, advice and assistance, data, images, tools, and assessment and monitoring systems to permit job performance with minimal support and intervention by others."

EPSS (Electronic Performance Support Systems) are systems that provide employees with the services, processes, information, advice and learning experiences they need to do their job and get up to speed as quickly as possible with the minimum of support from other people.

PCD infuses tools with knowledge, structures tasks, and enables performers to achieve the required level of performance as quickly as possible – at the very most, within a day -- with minimum support from other people.

Software that is designed around performance is intuitive to its users and enables them to perform their normal work with obvious gains in speed and efficiency without ever attending training classes or looking things up in books. It reflects their own conceptualization of their work and incorporates their language, idioms, metaphors, and understanding of how to perform tasks.

Intuit's Quicken is a good example. Virtually every user approaching the program and seeing a blank check on the screen knows intuitively what information needs to be input and where it goes. The same with the ledger and reconciliation. The program builds on knowledge its users already have.

Another way of grasping this central point is to consider how software is constructed. Winslow and Bramer of Andersen Consulting explain it like this:

Traditional transaction-based systems are designed with an emphasis on process and data modeling. In a way, they are designed inside-out. The user interface modeling is derived from the process and data structures. For example, the layout of screens is often a reflection of a record structure, and the menus of the system reflect the functional structure.

Performance systems are more interactive, and more oriented toward actual work circumstances. Thus, these systems need to be designed from the outside-in. The character of process and data modeling in itself does not change so much, but the (outside) user interface modeling drives the (internal) process modeling and data modeling.

In simpler terms, begin with what your workers are doing, with what you want them to do, and what support they need to be successful. Everything else about the system flows from that basic orientation. (1994, p. 62f.)

Or, as Gery puts it, "When designers have the point of the view of the performer situated in a real work context, success is inevitable. If the point of view does not closely match the situation, usability and performance problems are inevitable." (1995b, p. 31)

References - General

References - Instructional Technology

References - Commercial