In the legal domain, ontologies enjoy quite some reputation as a way to model normative knowledge about laws and jurisprudence. Several methods have been used and are well-known qua ontological methods. However, no previous attempt to construct ontologies based on professional knowledge exists, capturing judicial practical expertise. This paper shows the preliminary ontology development for the second version of the prototype Iuriservice, a web based intelligent FAQ for judicial use, containing a repository of professional judicial knowledge. The iFAQ system will focus on such knowledge and will base on OPLK -Ontology of Professional Legal Knowledge- developed by UAB. Profesional Legal Knowledge refers to the core of professional work that contains the experience of the daily treatment of cases and is unevenly distributed within individuals as a result of their professional and personal experiences. The knowledge acquisition process has been based on an ethnographic process designed by the UAB team and the Spanish School of the Judiciary within the national SEC project, to efficiently obtain useful and representative information from questionnaire-based interviews. Nearly 800 competency questions have been extracted from these interviews and the ontology is being modelled from the selection of relevant terms. Regarding ontology modelling issues, we have followed the DILIGENT argumentation methodology to control the discussion and trace the arguments used in favor or against the introduction of a concept X as part of the domain ontology. This paper presents the preliminary Ontology of Professional Judicial Knowledge (OPJK) that has been extracted manually from the selection of relevant terms from nearly 200 competency questions and affirms that the modelling of this professional judicial knowledge demands the description of this knowledge as it is perceived by the judge and the abandonment of dogmatic legal categorizations.