Hazards of Design "[w]hen most successful, ritual performance works by a circular logic in which it creatively brings about a context and set of identities that it portrays as already existing." Such is also the case of computer system design, whose first step is the articulation of a grammar of action for the site whose activities the system is to represent (Agre 1994). Designers present this ontology and grammar as already existing in the site, as structures already immanent in that site's activities. And yet much of the work of implementing a new computer system is arranging for the activities actually to conform to the ontology and grammar of action that the system inscribes, and moreover to do so accountably -- and not just accountably to the site's members but also for purposes of capture by the machine. From keypunch data entry to barcode readers and wireless handheld transaction units, technical means are proliferating for maintaining a correspondence between the unfolding structures of human activity and the accumulating data structures of the machines. This correspondence can only be established, however, so long as the activity is accountably isomorphic to the formal structures that the design process has inscribed.