A Model Driven Approach to the Analysis of Timeliness Properties

Abstract. The need for a design language that is rigorous but accessible and intuitive is often at odds with the formal and mathematical nature of languages used for analysis. UML and Petri Nets are a good example of this dichotomy. UML is a widely accepted modelling language capable of modelling the structural and behavioural aspects of a system. However UML lacks the mathematical foundation that is required for rigorous analysis. Petri Nets on the other hand have a strong mathematical base that is well suited for analysis of a system but lacks the appeal and ease-of-use of UML. Design in UML languages such as Sequence Diagrams and analysis in Petri Nets require on one hand some expertise in potentially two incompatible systems and their tools, and on the other a seamless transition from one system to the other. One way of addressing this impediment is to focus the software development mainly on the design language system and to facilitate the transition to the formal analysis by means of a combination of automation and tool support. The aim of this paper is to present a transformation system, which takes UML Sequence Diagrams augmented with time constraints and generates semantically equivalent Petri Nets that preserve the timing requirements. A case study on a small network is used in order to illustrate the proposed approach and in particular the design, the transformation and the analysis processes.

Quantitative Verification: Formal Guarantees for Timeliness, Reliability and Performance

Computerised systems appear in almost all aspects of our daily lives, often in safety-critical scenarios such as embedded control systems in cars and aircraft or medical devices such as pacemakers and sensors. We are thus increasingly reliant on these systems working correctly, despite often operating in unpredictable or unreliable environments. Designers of such devices need ways to guarantee that they will operate in a reliable and efficient manner. Quantitative verification is a technique for analysing quantitative aspects of a system's design, such as timeliness, reliability or performance. It applies formal methods, based on a rigorous analysis of a mathematical model of the system, to automatically prove certain precisely specified properties, e.g. ``the airbag will always deploy within 20 milliseconds after a crash'' or ``the probability of both sensors failing simultaneously is less than 0.001''. The ability to formally guarantee quantitative properties of this kind is beneficial across a wide range of application domains. For example, in safety-critical systems, it may be essential to establish credible bounds on the probability with which certain failures or combinations of failures can occur. In embedded control systems, it is often important to comply with strict constraints on timing or resources. More generally, being able to derive guarantees on precisely specified levels of performance or efficiency is a valuable tool in the design of, for example, wireless networking protocols, robotic systems or power management algorithms, to name but a few. This report gives a short introduction to quantitative verification, focusing in particular on a widely used technique called model checking, and its generalisation to the analysis of quantitative aspects of a system such as timing, probabilistic behaviour or resource usage. The intended audience is industrial designers and developers of systems such as those highlighted above who could benefit from the application of quantitative verification,but lack expertise in formal verification or modelling

Preliminary Evidence of the Effects of the Adoption of the Impairment-Only Approach to Goodwill Accounting in Sweden

We examine the effects of the implementation of the impairment-only approach to goodwill accounting on the financial reporting quality in Sweden after the adoption of IFRS. Using accounting data from public companies in Sweden, we test the value relevance and timeliness of the accounting information before and after the switch to IFRS. We compare the value relevance of accounting information between 2004 and 2005 to investigate the effects of the switch from goodwill amortization to the impairment-only approach. We find some weak evidence of an increase in the value relevance of accounting information among companies with substantial goodwill balances in proportion to total assets. However, we find no statistically significance in the incremental value relevance related to amortization charges, impairment charges, or intangible assets, on share prices between the two periods. Moreover, we find no evidence of increased timeliness or any association between timeliness in reported earnings in 2005 and impairment charges made in that year

Model-driven performance evaluation for service engineering

Service engineering and service-oriented architecture as an integration and platform technology is a recent approach to software systems integration. Software quality aspects such as performance are of central importance for the integration of heterogeneous, distributed service-based systems. Empirical performance evaluation is a process of measuring and calculating performance metrics of the implemented software. We present an approach for the empirical, model-based performance evaluation of services and service compositions in the context of model-driven service engineering. Temporal databases theory is utilised for the empirical performance evaluation of model-driven developed service systems

COMPREHENSIVE INCOME IN EUROPE: VALUATION, PREDICTION AND CONSERVATIVE ISSUES

The IASB comprehensive income project extends the ââ¬Ëfair value’ measurement conceptfrom the balance sheet into the income statement. This article extends prior research, primarilybased on Anglo-Saxon countries, by using a comprehensive data set of 56,700 European firm yearsover sixteen countries. We find that other comprehensive income provides incremental informationto investors ââ¬â due to unrealised available-for-sale securities component ââ¬â and affects analysts’decision to revise price estimates. On the other hand, traditional operating net income dominatesaggregated comprehensive income as a valuation metric and in predicting cash flows. Results arerobust to pooled and country specific regressions, controls for non-linearities, impact of reportingincentives, and the underlying accounting framework (local GAAP, US GAAP, IFRS). We also findthat aggregated comprehensive income switches the conservative attributes of income towards amore timely recognition of good news over bad news, reducing the conservative agency contractingrole. One possible explanation is the mixing of different concepts of operating capital incrementswith unrealised gains and realised historic net income. An agenda item for the IASB is how incomereporting should be disaggregated with a clear delineation on capital increments, conservativeoperating income, and unrealised financial gains. This is especially important in ContinentalEurope which relies to a greater extent on debt capital and has an under-developed corpus ofequity financial analysts.comprehensive income, value relevance, analyst forecast revisions, European IFRS, accountingconservatism

Board of directors' characteristics and conditional accounting conservatism : Spanish evidence.

Using a sample of Spanish listed firms for the period 1997-2002 we find that firms where the CEO has low influence over the functioning of the board of directors show a greater degree of accounting conservatism. We measure the influence of the CEO over the board of directors using two aggregate indexes combining 6 (8) characteristics of the functioning of the board of directors and its monitoring committees: board size, proportion of non-executive directors, proportion of independent directors, whether the chairman of the board is an executive director, the number of board meetings, and the existence of an audit committee, a nomination/remuneration committee and an executive committee. We define conservatism as the asymmetric recognition speed of good and bad news in earnings, and we measure it following Basu (1997) and Ball and Shivakumar (2005). Our results are robust to alternative specifications and specific controls for investment opportunities and for the endogenous nature of corporate governance and earnings quality. Overall, our evidence shows that firms with strong boards use conservative accounting numbers as a governance tool, even in an institutional setting with low litigation risk such as SpainConservatism; Governance; CEO; Board of Directors; Earnings Timeliness; Spain;