Towards the algebraic analysis of hyperlink structures

Structuring media objects such as text, graphics etc. by means of XML is a broadly discussed issue in hypermedia modeling. Thereby, an entire hypermedia document is not only arranged in such a way different developers may interchange data and have easy access to the inner structure of media objects by means of powerful tools available in the XML scene. Moreover, utilizing a given document structure to find new possibilities of linking documents is a major concern. Formal approaches, however, rarely appear in this context. In this paper, we contribute to formally structuring media objects and their linkage, thereby aiming at analyzing hyperlink structures. That is, properties of hyperlinks between media objects underlie a mathematical verification in advance of encoding the concrete hyperdocument. Algebraic specifications serve as a formal model allowing to obtain algebras reflecting hyperlink structures open to analysis

An Approach to Algebraic Semantics of Object-Oriented Languages

Studying the semantics of programming languages has a long tradition in computer science. Various approaches use various formalisms with various objectives. In the last two decades, algebraic specifications have requently been used to study functional as well as imperative languages, and, in particular, object-orientated ones, thereby often focusing on specific aspects and concepts of this programming paradigm. In this paper, we follow this tradition and develop an algebraic semantics of a sample object-oriented language. We thereby distinguish between the object-oriented concepts of the language to structure code, and the imperative ones to implement functionality and thus the algorithmic parts of the language. Therefore, our approach encompasses two steps: first, we develop an algebraic semantics of basic object-oriented principles, into which, secondly, the semantics of the language s imperative parts is embedded. Static semantic aspects are captured by structured algebraic specifications, whereas dynamic ones are reflected by many-sorted algebras. These aspects are treated as "second order" concepts and are thus interpreted within a model class of the underlying specification. The approach elaborated here can be employed to formalize the semantics of "standard" object-oriented languages such as Eiffel, Java, or C++

Message sequence charts in the software engineering process

The software development process benefits from the use of Message Sequence Charts (MSC), which is a graphical language for displyaing the interaction behaviour of a system. We describe canonical applications of MSC independent of any software development methodology. We illustrate the use of MSC with a case study: the Meeting Scheduler

Inductive Verification of Data Model Invariants for Web Applications ∗

Modern software applications store their data in remote cloud servers. Users interact with these applications using web browsers or thin clients running on mobile devices. A key issue in dependability of these applications is the correctness of the actions that update the data store, which are triggered by user requests. In this paper, we present techniques for automatically checking if the actions of an application preserve the data model invariants. Our approach first automatically data store, from a given application using instrumented execution. The abstract data store identifies the sets of objects and relations (associations) used by the application, and the actions that update the data store by deleting or creating objects or by changing the relations among the objects. We show that checking invariants of an abstract data store corresponds to inductive invariant verification, and can be done using a mapping to First Order Logic (FOL) and using a FOL theorem prover. We implemented this approach for the Rails framework and applied it to three open source applications. We found four previously unknown bugs and reported them to the developers, who confirmed and immediately fixed two of them