A clinical practice guideline is a knowledge uptake instrument that supports evidence-based decision making by clinicians. It represents a model of a clinical process that describes the sequence of actions, decisions and their outcomes, and the interface with other processes beyond the scope of a guideline. In domains outside healthcare, the computerization of business processes via information systems follows a very rigorous design labeled as the system development life cycle. Our argument is that the computerization of a clinical practice guideline is the equivalent of building an information system for a clinical process and therefore should follow a similarly rigorous design method. One of the first and also one of the most important steps in the system development life cycle is learning about user information requirements. This paper is about a user requirements elicitation and definition process customized to clinical practice guideline. We propose the novel ActCPG conceptual framework for elicitation of basic user requirements for developing computer-interpreted guidelines. This framework relies on Activity Theory to structure and decompose information coming from a clinical practice guideline and associated narrative. We illustrate operation of the ActCPG framework with an example of a practice guideline for a management of clinically obese children enrolled in the Children's Hospital of Eastern Ontario obesity program.