Crypt-equivalent algebraic specifications

Summary Equivalence is a fundamental notion for the semantic analysis of algebraic specifications. In this paper the notion of crypt-equivalence is introduced and studied w.r.t. two loose approaches to the semantics of an algebraic specification T: the class of all first-order models of T and the class of all term-generated models of T. Two specifications are called crypt-equivalent if for one specification there exists a predicate logic formula which implicitly defines an expansion (by new functions) of every model of that specification in such a way that the expansion (after forgetting unnecessary functions) is homologous to a model of the other specification, and if vice versa there exists another predicate logic formula with the same properties for the other specification. We speak of first-order crypt-equivalence if this holds for all first-order models, and of inductive crypt-equivalence if this holds for all term-generated models. Characterizations and structural properties of these notions are studied. In particular, it is shown that first order crypt-equivalence is equivalent to the existence of explicit definitions and that in case of positive definability two first-order crypt-equivalent specifications admit the same categories of models and homomorphisms. Similarly, two specifications which are inductively crypt-equivalent via sufficiently complete implicit definitions determine the same associated categories. Moreover, crypt-equivalence is compared with other notions of equivalence for algebraic specifications: in particular, it is shown that first-order cryptequivalence is strictly coarser than abstract semantic equivalence and that inductive crypt-equivalence is strictly finer than inductive simulation equivalence and implementation equivalence.     

Programming in a wide spectrum language: a collection of examples

The paper exemplifies programming in a wide spectrum language by presenting styles which range from non-operative specifications—using abstract types and tools from predicate logic as well as set theory—over recursive functions, to procedural program with variables. Besides a number of basic types, we develop an interpreter for parts of the language itself, an algorithm for applying transformation rules to program representations, a text editor, and a simulation of Backus' functional programming language.     

Natürliche geogene Grundwasserbeschaffenheit in Baden-Württemberg

In order to investigate natural groundwater quality in Baden-Württemberg, 250 water samples from wells and springs of catchments with only little anthropogenic influence were chemically analysed. The study focused on the quantitative analysis of trace elements from natural sources. To assess the influence of atmospheric deposition on groundwater quality over a period of one year, monthly precipitation samples obtained from five meteorologic stations were also analysed. The groundwater hydrochemical data were obtained from 15 different hydrogeochemical units. The analytical data from the precipitation samples provide valuable information regarding the concentration of several elements in the atmospheric deposition in Baden-Württemberg. For near-surface groundwater with only limited anthropogenic influence, concentration ranges for more than 50 hydrochemical parameters are now available. The results provide a reliable database of the natural variation of trace elements. Potential anthropogenic influences can thus be evaluated by comparing future data against this natural background. For illustration, the results from the trace elements cobalt and uranium are presented in more detail.     

An Ontology for Secure Web Applications

It is commonly known that most applications suffer from security holes that are sooner or later exploited. One reason is that for developers the term "security" is difficult to grasp. Many security properties exist and there are many methods to enforce them or to avoid implementing common vulnerabilities in applications. Ontologies can help to get an overview of web security and to structure this domain by relating relevant assets, methods, tools, security properties, vulnerabilities and threats (referred to as knowledge objects). In this paper, we present a novel ontology with a focus on secure web applications, called SecWAO. It is based on the Context model of SecEval, which is a domain model tailored to describe knowledge objects. By providing an overview, SecWAO supports teaching purposes and web developers when specifying security requirements or making design decisions.     

Hydrogeochemische Hintergrundwerte der Grundw?sser Deutschlands als Web Map Service

One of the main objectives of the EC water framework directive is to ensure good chemical status for all groundwater bodies. For this reason the geological surveys of Germany have produced a nationwide map of the background values of groundwater. Only naturally occurring inorganic parameters were taken into account, including the relevant major and trace elements. Based on the hydrogeological map of Germany at the scale of 1:200,000 (HüK 200), and its delimited hydrogeological regions, a total of 186 hydrogeochemical units were defined and mapped geochemically. This involved collection of more than 52,000 groundwater samples in a database and allocation to their appropriate hydrogeochemical units. In order to separate anomalies within the data-sets from the underlying normal population, probability nets were used as a statistical tool. The procedure allowed to determine the normal populations of the investigated parameters within the hydrogeochemical units and to quantify them in the form of percentiles. The resulting hydrogeochemical background values are accessible through an internet web map service that includes an online map application. The main intention of this technical note is to inform the reader about the existing internet service, which necessitates some web-site content duplication.     

Symptoms and complications of pertussis in adults

There is increasing evidence that pertussis occurs frequently in adults, but there is limited information on the clinical course of this disease beyond childhood. A household contact study on the efficacy of an acellular pertussis vaccine was used to study the symptoms of pertussis in adults. Among 257 patients with pertussis identified in 121 families during a two-year period in one study center with a low whole-cell pertussis-vaccine uptake, 79 (30.7%) were adults, aged 19-83 years (mean age: 36 years) with a 1:1.8 male to female ratio. Ninety-one percent of the adults suffered from coughing (mean duration: 54 days), and in 80% this cough lasted > or = 21 days. Whoops were rare (8%), whereas cough followed by vomiting and/or choking (53%) and cough disturbing sleep (52%) were common. This is the first report to describe sweating attacks as symptom of pertussis (14%). Pharyngeal symptoms (37%), influenza-like symptoms (30%), sneezing attacks (22%), hoarseness (18%), sinus pain (16%) and headaches (14%) were also observed. Various complications were seen in 23% of the patients. In order to minimize the spread of the organism, microbiological diagnostics should be vigorously applied to all symptomatic contacts of a patient with pertussis but also to all patients with long lasting cough-irrespective of age.     

Specification and refinement of mobile systems in MTLA and mobile UML

We define the spatio-temporal logic MTLA as an extension of Lamport's Temporal Logic of Actions TLA for the specification, verification, and formal development of systems that rely on mobile code. The formalism is validated by an encoding of models written in the mobile UML notation. We identify refinement principles for mobile systems and justify refinements of mobile UML state machines with the help of the MTLA semantics.