1084067
On exceptions as first-class objects in Ada 95
This short position paper argues that it might be beneficial to try to bring the exception model of Ada 95 more in-line with the object-oriented model of programming. In particular, it is felt that exceptions --- being such an important concept for the development of fault-tolerant software --- have deserved a promotion to first-class objects of the language. It is proposed to resolve the somewhat awkward dichotomy of exceptions and exception occurrences as it exists now in Ada 95 by treating exceptions as (tagged) types, and exception occurrences as their instances.
41947706
Secure Communication in Distributed Ada
This document describes an implementation of secure communication for distributed applications in Ada 95. It explains the basics of cryptography and introduces the problem of key exchange. After a brief description of distributed systems in Ada 95, the modular structure of the implementation and the way it handles key distribution is presented.
196094
Integrating object-oriented programming and protected objects in Ada 95
Integrating concurrent and object-oriented programming has been an active research topic since the late 1980's. There is a now a plethora of methods for achieving this integration. The majority of approaches have taken a sequential object-oriented language and made it concurrent. A few approaches have taken a concurrent language and made it object-oriented. The most important of this latter class is the Ada 95 language, which is an extension to the object-based concurrent programming language Ada 83. Arguably, Ada 95 does not fully integrate its models of concurrency and object-oriented programming. For example, neither tasks nor protected objects are extensible. This article discusses ways in which protected objects can be made more extensible.
23941957
Model Checking
Die Gewährleistung der korrekten
Funktionsweise von Hard- und Software ist ein entscheidender
Faktor bei der heutigen Systementwicklung. Dies trifft ganz
besonders auf das Gebiet der sog. „sicherheitskritischen“
Systeme zu, bei dem ein Systemversagen Menschenleben gefährden
kann.
45184054
A package for the analytic investigation and exact solution of differential equations
To find exact solutions of differential equations fDEs) one usually performs a variety of tests and ansaetze as e.g. the symmetry ansatz, separation ansatz, ansaetze for first integrals. When carrying through these ideas one h a s to solve overdetermined systems of partial DEs fPDEs). Whereas the formulation of the overdetermined system f o r each ansatz is achieved by different programs we use one program to investigate the overdetermined sys~. This program CRAOKSTAR contains three basic modules for the deooupling of DEs, for the integration of exact DEs and f o r separation. They are explained by examples. With these new a b i l i t i e s i t becomes poss ib le f o r CRACKSTAR to so lve systems of DEs which are sore difficult, i.e. the ansatz to be carried through ma y be less restrictive. An example shows that in this way not only point s y m m e t r i e s b u t a l s o m o r e g e n e r a l d y n a m i c a l s y m m e t r i e s o f o r d i n a r y DEs ( O D E s ) c a n b e d e t e r m i n e d . F o r t h e I n v e s t i g a t i o n o f L l e s ~ t r i e s o f systems of PDEs an interval strategy is applied which reduces the effort f o r GKACKSTM~ c o n s i d e r a b l y . F u r t h e r t w o new c o n c e p t s , a n i n t e g r a l a n s a t z f o r ODEs and a generalized separation ansatz f o r PDEs are described as w e l l a s t h e p r o g r a m s w h i c h g e n e r a t e o v e r d e t e r m i n e d s y s t e m s for e a c h ansatz.
19107527
Investigating DEs with CRACK and related programs
The aim of the package to be described is to try modularizing the investigation of differential equations for which there are no complete algorithms available yet. All, that is available for such problems are algorithms for special situations, e.g. when first integrals with a simple structure exist (e.g. polynomial in first derivatives) or when the problem has infinitesimal symmetries. In all such cases, finally a system of differential equations has to be solved which is overdetermined in the sense that more conditions have to be satisfied than there are unknown functions. To do a variety of such investigations efficiently, like a symmetry analysis, application of symmetries, determination of first integrals, differential factors, equivalent Lagrangians, the strategy is to have one package (CRACK) for simplifying DEs and solving simple DEs as effective as possible and to use this program as the main tool for all the above mentioned investigations. For each investigation there is then only a short program necessary to just formulate the necessary conditions in form of an overdetermined DE-system and to call CRACK to solve this, possibly in a number of successive calls. The examples below shall indicate the range of possible applications.
43214033
Ein neuer Ansatz zur Lösung der Phasenentfaltungsproblematik
Ein durch eine harmonische Intensitatsverteilung beschreibbares Streifenmuster soll ausgewertet werden. Dabei mus fur jeden Punkt des Musters die Phasenlage bestimmt werden. Mit auto-matischen Phasenauswertemethoden last sich im allgemeinen die Phase nur im sich periodisch fortsetzenden Werteintervall [−π, π] bestimmen (Sagezahnbild). Das Zusammensetzen zur Gesamtphase wird als Phasenentfaltung bezeichnet. Die Anwendung des Streifenprojektions-verfahrens [Breu93] zur Konturbestimmung von Schaumstoffoberflachen in Kombination mit der Phasenshifttechnik fuhrt zu einem Sagezahnbild, dessen automatische Entfaltung bei Anwendung von ublichen Methoden zu erheblichen Fehlern fuhrt. Oftmals ist nur eine interaktive Phasenkorrektur durch den Benutzer moglich. Mit Hilfe der Fuzzy-Logik kann man das menschliche Expertenwissen in einer vom Computer verarbeitbaren Form fur die automatische Phasenentfaltung zur Verfugung stellen.
3233905
Programs for applying symmetries
In this paper the programs APPLYSYM, QUASILINPDE and DETRAFO are described which aim at the utilization of infinitesimal symmetries of differential equations. The purpose of QUASILINPDE is the general solution of quasilinear PDEs. This procedure isusedby APPLYSYM fortheapplication of point symmetries for either Q calculating simila,rity variables toperform a point transformation which lowers the order of an ODEoreffectiveiy reduces the number of explicitly occuringindependent variablesin aPDE(-system) or for . generalizing given special solutions of ODEs/PDEs with new constant parameters. The program DETRAFO performs arbitrary pointand contact transformations of ODEs/PDEs and is applied if similarity and symmetry variables have been found. The program APPLYSYM is used in connection with the program LIEPDE for formulating and solving the conditions for pointand cent act symmetries which is described in [4]. The actual problem solving is done in all these programs through a call to the package CRACK for solving overdetermined PDE systems.