At the beginning of the practice-oriented legal informatics of the seventies, it was undertaken to apply programming techniques also for the representation of legal content. Wolfgang Kahlig's attempt to see the concepts of housing law in a formal scheme can be understood from this methodological approach. Its central element is to bring about a decision controlled by conditions. This is not a visualisation of housing law in a narrower sense, as the terms of this area of law are not presented simultaneously in a visible context, but rather a formal meta-level procedure to sequentially clarify the applicability of the terms of housing law for subsuming the facts of the case, a highly important procedure in practice. There are two prerequisites for the decision, on the one hand the facts of the case (the legal situation) and on the other hand the facts of the case (the factual situation). The decision itself first cognitively establishes the relational third party in subsumption by structurally weighing the two in order to then cognitively-volitively make the decision. The practical significance of Kahlig notation lies in the fact that only in very few cases has it been possible to prepare the legal decision-making activity on a formal basis, supported by explicit logical methods, to build a bridge, as it were, between the textual shore of the law and the situational shore of legal reality (before and after the decision). The concern of legal visualisation, however, goes beyond a conceptual decision-making process on the meta-level, as demonstrated in the legal visualisation session of IRIS. The spectrum of visualisation possibilities here ranges from a formal deepening of conceptual structures, to factual visual representations, to the additional integration of virtual worlds.