Many concurrency control algorithms have been proposed for use in distributed database systems. Despite the large number of available algorithms, and the fact that distributed database systems are becoming a commercial reality, distributed concurrency control performance tradeoffs are still not well understood. In this paper we attempt to shed light on some of the important issues by studying f...

In the social sciences, performance of two groups is frequently compared based on a cognitive test involving binary items. Item response models are often utilized for comparing groups. However, presence differential item functioning (DIF) can impact group comparisons. order to avoid biased estimation groups, appropriate statistical methods handling required. This article compares performance-re...

BACKGROUND We tested the properties of the 18 Household Food Security Survey (HFSS) items, and the validity of the resulting food security classifications, in an English-speaking middle-income country. METHODS Survey of primary school children in Trinidad and Tobago. Parents completed the HFSS. Responses were analysed for the 10 adult-referenced items and the eight child-referenced items. Ite...

This study investigates the performance of estimation methods for multidimensional IRT models with dichotomous and polytomous data in two well-known programs: SAS PROC mirt package R. A simulation was used to compare on a simple structure Rasch model, complex 2PL bifactor graded response model. Under RMSE bias criteria regarding item parameter recovery, showed nearly identical condition. When u...

Over the years several locking protocols have been proposed for coordinating the concurrent use of a data base by multiple transactions. Of these, the non-two-phase locking (non-2PL) protocols form a large class. The Pitfall Protocol (PP) is one of the non-2PL protocols. While the rules of PP assure serializability, they do not prevent deadlocks from occurring. Resolution of a deadlock by parti...

This introduction to the R package plink is a (slightly) modified version of Weeks (2010), published in the Journal of Statistical Software. The R package plink has been developed to facilitate the linking of mixed-format tests for multiple groups under a common item design using unidimensional and multidimensional IRT-based methods. This paper presents the capabilities of the package in the co...

Database systems for real-time applications must satisfy timing constraints associated with transactions, in addition to maintaining data consistency. In addition to real-time requirements, security is usually required in many applications. Multilevel security requirements introduce a new dimension to transaction processing in real-time database systems. In this paper, we argue that because of ...

The present study aims to compare the Kernel equating and local methods in observed score equating. Functions error estimates regarding difference between raw equated scores by Stocking-Lord Haebara true-score were examined Item Response Theory Observed Score Equating. Therefore, 5, 10, 15 external anchor items used, obtained from two forms based on 2PL model. R (version 3.5.3.) programming sof...

Multiversion two-phase locking (MV2PL) provides on-line serializable queries without introducing the long blocking delays that can occur with conventional two-phase locking (2PL). MV2PL requires indexing structures, however, that are capable of supporting multiple versions of data. In this paper, we present several options for extending single-version indexing schemes for use with MV2PL. These ...