The concept of information retrieval (IR) could be extended towards an open information retrieval (Open IR) approach. Open IR gives users a wider range of access methods when retrieving business objects (e.g. projects, products, skills, people, deliverables...) using Web applications. Open IR is based on the concept of the "entity", as defined in the hypertopic model. The hypertopic model is a knowledge representation language we propose for mediating various "socio-semantic Web" applications, using topic maps co-constructed by members of a community. We briefly describe in this paper how hypertopic "entities" can be viewed "semiotically", depending on various topics and points of view. We describe how entity-based hypertopic maps can be used to facilitate users' search efforts. For this purpose, we illustrate Open IR in the field of e-commerce: we examine complex features which could be proposed on electronic market places to describe/retrieve entities such as products proposed by multiple providers.