Architectural conservation describes the process through which the material, historical, and design integrity of humanity's built heritage are prolonged through carefully planned interventions. The individual engaged in this pursuit is known as an architectural conservator-restorer. Decisions of when and how to engage in an intervention are critical to the ultimate conservation-restoration of cultural heritage. Ultimately, the decision is value based: a combination of artistic, contextual, and informational values is normally considered. In some cases, a decision to not intervene may be the most appropriate choice.