Bad news on decision problems for patterns

We study the inclusion problem for pattern languages, which is shown to be undecidable by Jiang et al. (J. Comput. System Sci. 50, 1995). More precisely, Jiang et al. demonstrate that there is no effective procedure deciding the inclusion for the class of all pattern languages over all alphabets. Most applications of pattern languages, however, consider classes over fixed alphabets, and therefore it is practically more relevant to ask for the existence of alphabet-specific decision procedures. Our first main result states that, for all but very particular cases, this version of the inclusion problem is also undecidable. The second main part of our paper disproves the prevalent conjecture on the inclusion of so-called similar E-pattern languages, and it explains the devastating consequences of this result for the intensive previous research on the most prominent open decision problem for pattern languages, namely the equivalence problem for general E-pattern languages

Bad news on decision problems for patterns

We study the inclusion problem for pattern languages, which - due to Jiang et al. (Journal of Computer and System Sciences 50, 1995) - is known to be undecidable. More precisely, Jiang et al. demonstrate that there is no effective procedure deciding the inclusion for the class of all pattern languages over all alphabets. Most applications of pattern languages, however, consider classes over fixed alphabets, and therefore it is practically more relevant to ask for the existence of alphabet-specific decision procedures. Our first main result states that, for all but very particular cases, this version of the inclusion problem is also undecidable. The second main part of our paper disproves the prevalent conjecture on the inclusion of so-called similar E-pattern languages, and it explains the devastating consequences of this result for the intensive previous research on the most prominent open decision problem for pattern languages, namely the equivalence problem for general E-pattern languages

Inclusion problems for patterns with a bounded number of variables

We study the inclusion problems for pattern languages that are generated by patterns with a bounded number of variables. This continues the work by Freydenberger and Reidenbach [D.D. Freydenberger, D. Reidenbach, Bad news on decision problems for patterns, Information and Computation 208 (1) (2010) 83-96] by showing that restricting the inclusion problem to significantly more restricted classes of patterns preserves undecidability, at least for comparatively large bounds. For smaller bounds, we prove the existence of classes of patterns with complicated inclusion relations, and an open inclusion problem, that are related to the Collatz Conjecture. In addition to this, we give the first proof of the undecidability of the inclusion problem for NE-pattern languages that, in contrast to previous proofs, does not rely on the inclusion problem for E-pattern languages, and proves the undecidability of the inclusion problem for NE-pattern languages over binary and ternary alphabets. © 2012 Elsevier Inc

Disclosure of Maternal HIV Status to Children: To Tell or Not To Tell . . . That Is the Question

HIV-infected mothers face the challenging decision of whether to disclose their serostatus to their children. From the perspective of both mother and child, we explored the process of disclosure, providing descriptive information and examining the relationships among disclosure, demographic variables, and child adjustment. Participants were 23 mothers and one of their noninfected children (9 to 16 years of age). Sixty-one percent of mothers disclosed. Consistent with previous research, disclosure was not related to child functioning. However, children sworn to secrecy demonstrated lower social competence and more externalizing problems. Differential disclosure, which occurred in one-third of the families, was associated with higher levels of depressive and anxiety symptoms. Finally, knowing more than mothers had themselves disclosed was related to child maladjustment across multiple domains. Clinical implications and the need for future research are considered

The impact of political announcements on expectations concerning the starting date of the EMU - A microeconometric approach to the detection of event-dependent answering patterns in business surveys

This paper examines German business survey data to uncover the influence of political news on expectations concerning the starting date of the European Monetary Union (EMU). In this survey the participants were asked to indicate whether they expect a punctual or a delayed start of the EMU. Alternatively, they could also tick a don't know category. It is shown that political news actually influence answering patterns. While good news have a negative impact on the probability to cross don't know, they do not influence the probability to expect a delayed EMU start. Bad news, such as the heated debate about the convergence criteria at the Amsterdam EU summit, have a positive impact on the probability to expect a delayed start. The empirical results show that survey results generally have to be carefully interpreted if news about the topic which is investigated in the survey occur. If answering patterns are actually influenced by such news, the usual way to interprete survey responses - treating them as if they were sent back at the very same day - can lead to severe misunderstandings. In this paper a simple microeconometric technique is suggested which makes it possible to detect if survey responses are affected by news. --Binomial probit model,Expectations,European Monetary Union,Event-dependent answering patterns,Survey data

To Trade or Not to Trade: The Strategic Trading of Insiders around News Announcements

We argue that insiders' decisions to trade in short windows before news announcements are likely to result from a trade-off between the incentives to capitalize on the foreknowledge of the disclosure and the risk of regulatory scrutiny and lost reputation. We provide evidence that insider buying is driven by the trade-off, while selling is primarily influenced by the deterring effect of the regulatory and reputation risks. We show that insiders strategically choose the amount of shares bought ahead of good news announcements. They increase their purchases as the price impact of the news goes up, but we find that the amount of shares purchased levels off as the news becomes extreme. In contrast, we find that the probability of insider selling significantly decreases with the price impact of the forthcoming bad news. To further support our arguments on the importance of incentives and disincentives to trade, we show that the strategic trading is mainly observed in the most price-sensitive groups of news announcements, it is clearly pronounced for best informed executives (CEOs), and that trading patterns change with changes in regulations, and insiders with higher reputation at risk limit their trading ahead of bad news.insider trading, private information, information disclosure, regulation