Post-development change requests are user requirements for information systems changes after development. Conflicts might occur as contradictive or inconsistent relationships between requests and existing system design. Detecting conflicts in post-developmenet change requests is an important task during requests management processes. To address this topic, this article proposes an ontology-based blog for automatically discovering conflicts in the extended use-case models of requests from users. This study proposed an information system maintenance process. The proposed approach applies ontologies to represent domain knowledge. A set of rules are used to detect conflicts. This study developed a prototype and invited two companies to evaluate it. Usage feedback opinions about ontology-based blog from two companies indicated the usefulness. The ontology-based blog is a relatively new approach which bridge requirements blogs with a formal and machine interpretable representational model. The automatic conflicts detection capability of the ontology-based blog can reduce the labor cost in requirements analysis phase.