A domain-independent platform of spoken dialogue systems is presented. It assumes that information query is done by a sequence of key-phrases corresponding to search keys, which can be defined by a domain database. A GUI is incorporated to display typical phrase patterns for guidance and to promptly present recognition and query results for confirmation. The platform consists of general-purpose speech understanding modules and task specification tools that semi-automatically derive a lexicon and dialogue management rules from the domain database. It is applied to two different domains: hotel search system and literature search system. It drastically saves the labor cost and time in developing the prototype systems. And the strategy of key-phrase-based dialogue is even more effective than the conventional tuned system.