Interactions between systems constitute a common source of difficulty and complication in building, implementing, and maintaining IT-reliant work systems in organizations. Although a great deal has been published about systems analysis and design, most of the attention in that literature focuses on creating software specifications for a specific IT system. Relatively little attention focuses on direct and/or indirect interactions and conflicts between the IT-reliant work systems through which organizations operate. This paper proposes that work system co-existence, alignment, and coordination should receive more attention in systems analysis and design. Its main contribution is an initial set of taxonomies related to work system co-existence, alignment, and coordination. Key concepts include system interactions, intentionality of interactions, directness of interactions, explicitness of interactions, persistence of interactions, alignment of work systems, and congruence of work systems.