A b s t r a c t . Formal Concept Analysis, developed during the last fifteen years, has been based on the dyadic understanding of a concept constituted by its extension and its intension. The pragmatic philosophy of Charles S. Peirce with his three universal categories, and experiences in data analysis, have suggested a triadic approach to Formal Concept • C Y which is maximal with respect to component-wise inclusion. The triadic concepts are structured by three quasiorders given by the inclusion order within each of the three components. In analogy to the dyadic case, we discuss how the ordinal structure of the triadic concepts of a triadic context can be analysed and graphically represented. A basic result is that those structures can be understood order-theoretically as "complete trilattices" up to isomorphism. Triadic C o n t e x t sFormal Concept Analysis views concepts as means of intersubjective understanding in situations of purpose-oriented action. The formalization of concepts and concept systems shall especially support the interpretation and communication of conceptual relationships in different situations. This requires that the formalization of concepts has to be transparent and simple, but also comprehensive so that all main aspects of a concept may have explicit references in the formal model.The extensional and the intensional aspect, which were made explicit first by the "Port Royal Logic" [AN62] in the 17th century, are basic for the developed dyadic approach to Formal Concept Analysis. This approach starts with the primitive notion of a formal context as a triple (G, M, I) where G is a set of (formal) objects and M is a set of (formal) attributes, while I is a relation between G and M indicating when an object g of G has a certain attribute m of M. Formal contexts are often described by a two-dimensional cross table with a cross in position (g, m) if the relationship gIm holds, i.e., if the object g has the attribute m. A formal concept of a formal context (G, M, I) is defined as

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Carcinoembryonic antigen (CEA) levels were determined in 114 patients with confirmed lung cancer at the time of diagnosis using the CEA Ire-Sorin radioimmunoassay. Elevated CEA values were found in 47%. Most of the patients with high CEA levels had clinically detectable metastases. Ferritin was detectable by the Laurell-electrophoresis in the serum of 58 out of 81 (72%) of the patients with confirmed lung cancer at the time of diagnosis. Ferritin levels were significantly higher in patients with metastases. Serial measurements of CEA and ferritin during radio- and chemotherapy showed that the assay may be useful to evaluate the effects of therapy. Because of some false negative results both CEA and ferritin determinations should be used only in context with other clinical and laboratory findings.

An immunoprecipitation procedure is presented for the measurement of rat intestinal alkaline phosphatase (I-AP) in feces. Controls exhibit a logarithmic normal distribution of fecal I-AP. Single administration of an agent toxic for small intestinal mucosa like bleomycin or triparanol induces an increase of fecal I-AP on the 1st day and a marked reduction of I-AP activity on the following 3 days. After the 5th day, abnormal high fecal I-AP activities were observed during regeneration. In parallel, morphometry and measurements of I-AP activity in the homog-enate of small intestinal mucosa were performed. Rat fecal I-AP excretion proved to be a simple, non-invasive, sensitive marker for toxic damage of the small intestinal mucosa.