This paper builds an abductive argument for the existence of a working model personal to each knowledge worker which it bases on long-established cybernetic principles of control and regulation. The paper demonstrates what a working model needs to encompass, notably the individual herself as she crafts her personal work system PWS and her supporting personal information management system PIMS. The essential characteristics of a PIMS are identified. Conceprocity, concept process reciprocity, models are introduced and the example of the first author is used as a means of illustrating a Working Model. An appendix presents further details of the Conceprocity modelling language.