A ubiquitous Knowledge Base (u-KB) is a distributed and decentralized knowledge base where the factual knowledge (i.e. individuals) is scattered among objects disseminated within the environment with no centralized coordination. This paper presents an extended framework to enable u-KBs in mobile scenarios where a semantic discovery is carried out using metadata stored in RFIDs without fixed repositories. A dissemination protocol allows an on-demand retrieval of suitable descriptions directly from tags located on the objects. Such a vision allows to build a truly pervasive environment where autonomous objects compose a self-organized evolving discovery architecture suitable for u-Commerce purposes