Transaction Support for DataWeb Applications - A Requirement\u27s Perspective

W eb-based purely providing read-only access to information in terms of static HTML pages. Rather, more and more web-based information systems store (part of) the information within a database system (DBS) and generate HTML pages on demand. Such information systems are often called DataWeb Applications. Different users interact with the system, and often they perform changes concurrently. As an example in the area of electronic commerce, consider a web-based tourism information system, where an unpredictable number of a priori unknown tourists are allowed to book various tourism facilities at the same time. Whereas financial and security issues of such electronic commerce transactions are extensively discussed in literature, very few work exists on the database transaction aspect in terms of consistency and reliability of electronic commerce transactions and of DataWeb applications in general. The objective of this paper is to discuss the specific requirements that different architectures of DataWeb applications and the web itself pose on transaction management, and to identify promising technologies for enabling web transaction services

Characterization of biochars produced from pyrolysis of pelletized agricultural residues

Biochars produced from pelletized grape vine (GV) and sunflower husk (SFH) agricultural residues were studied by pyrolysis in a batch reactor at 400 and 500°C. Chemical and physical evolution of the biomass under pyrolysis conditions was determined and the products were characterized, including the main gaseous organic components. . Results showed a decrease in solid biochar yield with increasing temperature. Biochar is defined as a "porous carbonaceous solid" produced by thermochemical conversion of organic materials in an oxygen depleted atmosphere, which has physiochemical properties suitable for the safe and long-term storage of carbon in the environment and, potentially, soil improvement. The aim of this work is to improve the knowledge and acceptability of alternative use of the biochar gained from agro-forestry biomass residuals, such as grape vine and sunflower husks, by means of modern chemical and physical characterization tools

The Benefits of Open Hypermedia Systems Using Advanced Database Concepts

Large engineering enterprises are just one application area of open hypermedia systems (OHS), which are characterized by both, open hyperbase and link server functionality. An open hyperbase allows besides others to store and retrieve an extensible set of hypermedia objects. A link server allows to store and retrieve connectivity information and supports consistency management thereof. To provide these functionalities, open hypermedia systems have to tackle several important issues such as interoperability, extensibility, and computation. Using advanced database concepts as OHS baseline architecture these issues can be elegantly resolved. In particular, this paper proposes an OHS architecture based on an active object-oriented database system as well as SGML/HyTime as standardized interchange formats. By using active object-oriented database systems extensibility and computation including consistency management are ensured. By using international standards interoperability of hypermedi..

Implementing Business Policies Based on a Framework of Rule Patterns

Introduction Application development has to cope with frequently changing requirements which are to a large extent due to changes in the business environment [Loucopoulos et al. 1991]. These facets of business environments are often referred to as business policies. They may be based on ethics, law, culture and organizational commitments by either prescribing a certain action or by constraining the set of possible actions [Odell 1994]. Two main problems arise in the context of implementing business policies. Firstly, business policies are often blurred with code for implementing the basic, unchanging functionality of an application. This makes it difficult to cope with their dynamic nature. This problem can be resolved by factorising out business policies from single applications and representing them in terms of Event/Condition/Action rules (ECA rules). These rules allow the designer to monitor situations represented by event

Coordination in Workflow Management Systems - A Rule-Based Approach

Coordination is a key requirement of software systems where different parts have to be adjusted in order to reach a common goal. A prominent example thereof are workflow management systems (WFMS). They in particular require flexible mechanisms to realize different kinds of coordination, which are called coordination policies. This need for flexibility emerges from the fact that coordination policies in WFMS are subject to frequent changes caused by the business environment. Flexibility is required in different directions, ranging from a dynamic evolution of existing policies to proper reactions to unpredictable situations. Active object-oriented database systems (AOODBS) along with their basic mechanism in terms of Event/Condition/Action (ECA) rules seem to be a promising technology in order to cope with these requirements. ECA rules allow for an event-driven realization of context- and time-dependent behavior which constitutes a major property of coordination policies. By encapsulatin..

Flue Gas Recirculation During Poultry Litter Combustion in a Fixed Bed Lab-Scale Batch Reactor

This study focuses on the combustion behaviour of poultry litter which was experimentally studied in a fixed bed lab-scale reactor. The combustion experiments not only provided useful insights pertaining to the thermal decomposition of poultry litter over time, release of main gaseous compounds and nitrogen (N) species, but also the release of elements found initially in the ash composition. The main gaseous species were released during the devolatilisation phase, whereas Ammonia (NH3) was found to be the most abundant compound of N-gaseous species (45%) followed by nitrogen oxide (NO) with a fraction of ~10%. Alkali metals showed moderate release rates, whilst Chlorine (Cl) was observed to have the highest one (90%) of the ash forming elements, depicting the high volatility of the specific compound

Rule Patterns for Designing Active Object-Oriented Database Applications

Active object-oriented database systems (AOODBSs) have become widely recognized for smoothly capturing the context-dependent and time-dependent organizational knowledge of large enterprises, also known as business policies. However, not least since the remarkable panel at the RIDE'94 workshop on active database systems [Wido94] the design issue of AOODBS applications is known as one of the most pressing open research problems. This is largely because of the expressive power and flexibility of existing active object-oriented data models together with a lack of design guidelines on how to apply these models. Learning from analogous problems in object-oriented system development and borrowing their solution metaphor we introduce rule patterns as generic rule-based solutions for realizing business policies. The advantages of rule patterns are their predefined, reusable, and dynamically customizable nature allowing the designer to reuse existing experience for building AOODBS applications..