144,230 research outputs found
Web-GIS models: accomplishing modularity with aspects
Spatial concerns of Web geographical information systems (Web-GIS) are inherently crosscutting and volatile: crosscutting because they affect multiple functionalities of Web-GIS systems, and volatile because their status may change often. If these concerns are not modularized properly, the quality of Web-GIS services, particularly with regard to adaptation and evolution, can be severely compromised. This paper uses aspect-orientation to model crosscutting and volatile spatial concerns. By modeling both types of concerns, crosscutting and volatile, as candidate aspects, one can use dynamic weaving to add or remove them from a system at runtime. The aspect-oriented approach proposed starts with the identification and specification of crosscutting concerns and follows by composing these using modeling aspects using a transformation approach, an aspect-oriented modeling technique. The conflicts that can emerge due to the composition order are also taken into consideration. Finally, this paper proposes a set of reusable GIS crosscutting concerns, documenting them in a concern catalogue.Laboratorio de Investigación y Formación en Informática Avanzad
Identifying and Modelling Complex Workflow Requirements in Web Applications
Workflow plays a major role in nowadays business and therefore its
requirement elicitation must be accurate and clear for achieving the solution
closest to business’s needs. Due to Web applications popularity, the Web is becoming
the standard platform for implementing business workflows. In this
context, Web applications and their workflows must be adapted to market demands
in such a way that time and effort are minimize. As they get more popular,
they must give support to different functional requirements but also they
contain tangled and scattered behaviour. In this work we present a model-driven
approach for modelling workflows using a Domain Specific Language for Web
application requirement called WebSpec. We present an extension to WebSpec
based on Pattern Specifications for modelling crosscutting workflow requirements
identifying tangled and scattered behaviour and reducing inconsistencies
early in the cycle
A Peer-to-Peer Middleware Framework for Resilient Persistent Programming
The persistent programming systems of the 1980s offered a programming model
that integrated computation and long-term storage. In these systems, reliable
applications could be engineered without requiring the programmer to write
translation code to manage the transfer of data to and from non-volatile
storage. More importantly, it simplified the programmer's conceptual model of
an application, and avoided the many coherency problems that result from
multiple cached copies of the same information. Although technically
innovative, persistent languages were not widely adopted, perhaps due in part
to their closed-world model. Each persistent store was located on a single
host, and there were no flexible mechanisms for communication or transfer of
data between separate stores. Here we re-open the work on persistence and
combine it with modern peer-to-peer techniques in order to provide support for
orthogonal persistence in resilient and potentially long-running distributed
applications. Our vision is of an infrastructure within which an application
can be developed and distributed with minimal modification, whereupon the
application becomes resilient to certain failure modes. If a node, or the
connection to it, fails during execution of the application, the objects are
re-instantiated from distributed replicas, without their reference holders
being aware of the failure. Furthermore, we believe that this can be achieved
within a spectrum of application programmer intervention, ranging from minimal
to totally prescriptive, as desired. The same mechanisms encompass an
orthogonally persistent programming model. We outline our approach to
implementing this vision, and describe current progress.Comment: Submitted to EuroSys 200
Shuttle on-orbit contamination and environmental effects
Ensuring the compatibility of the space shuttle system with payloads and payload measurements is discussed. An extensive set of quantitative requirements and goals was developed and implemented by the space shuttle program management. The performance of the Shuttle system as measured by these requirements and goals was assessed partly through the use of the induced environment contamination monitor on Shuttle flights 2, 3, and 4. Contamination levels are low and generally within the requirements and goals established. Additional data from near-term payloads and already planned contamination measurements will complete the environment definition and allow for the development of contamination avoidance procedures as necessary for any payload
Exploiting a Goal-Decomposition Technique to Prioritize Non-functional Requirements
Business stakeholders need to have clear and realistic goals if they want to meet commitments in application development. As a consequence, at early stages they prioritize requirements. However, requirements do change. The effect of change forces the stakeholders to balance alternatives and reprioritize requirements accordingly. In this paper we discuss the problem of priorities to non-functional requirements subjected to change. We, then, propose an approach to help smooth the impact of such changes. Our approach favors the translation of nonoperational specifications into operational definitions that can be evaluated once the system is developed. It uses the goal-question-metric method as the major support to decompose non-operational specifications into operational ones. We claim that the effort invested in operationalizing NFRs helps dealing with changing requirements during system development. Based on\ud
this transformation and in our experience, we provide guidelines to prioritize volatile non-functional requirements
A Framework for Evaluating Model-Driven Self-adaptive Software Systems
In the last few years, Model Driven Development (MDD), Component-based
Software Development (CBSD), and context-oriented software have become
interesting alternatives for the design and construction of self-adaptive
software systems. In general, the ultimate goal of these technologies is to be
able to reduce development costs and effort, while improving the modularity,
flexibility, adaptability, and reliability of software systems. An analysis of
these technologies shows them all to include the principle of the separation of
concerns, and their further integration is a key factor to obtaining
high-quality and self-adaptable software systems. Each technology identifies
different concerns and deals with them separately in order to specify the
design of the self-adaptive applications, and, at the same time, support
software with adaptability and context-awareness. This research studies the
development methodologies that employ the principles of model-driven
development in building self-adaptive software systems. To this aim, this
article proposes an evaluation framework for analysing and evaluating the
features of model-driven approaches and their ability to support software with
self-adaptability and dependability in highly dynamic contextual environment.
Such evaluation framework can facilitate the software developers on selecting a
development methodology that suits their software requirements and reduces the
development effort of building self-adaptive software systems. This study
highlights the major drawbacks of the propped model-driven approaches in the
related works, and emphasise on considering the volatile aspects of
self-adaptive software in the analysis, design and implementation phases of the
development methodologies. In addition, we argue that the development
methodologies should leave the selection of modelling languages and modelling
tools to the software developers.Comment: model-driven architecture, COP, AOP, component composition,
self-adaptive application, context oriented software developmen
A Buffer Stocks Model for Stabilizing Price of Commodity under Limited Time of Supply and Continuous Consumption
Staple foods, in developing countries especially in Indonesia, have extremely volatile among harvest
and planting season caused by inelastic of supply-demand and price disparity. When a staple food is shortage
in market, it will trigger crisis of economics, political and social because it concerns with food security. This
paper develops a buffer stock model for stabilizing price of commodity under limited time of supply and
continuous consumption. The performance criterion of model will consider financial loss of producer, consumer
and government side when market is interfered by price-stabilization program and price-support program
simultaneously. The price fluctuation will be stabilized by market operation where buffer stocks are bought
from domestic and import supply point. This paper provides a price band policy that attempts to bound
domestic price variation between a set of upper and lower bounds on the level of domestic prices. We consider
three sets of problems reflecting different three prices elasticity from 4 period of supply and demand.
Numerical examples are found to be consistent with empirical estimates regarding the relationship price
elasticity with price band and with government budget for the agenda of assisting household to assure
availability a staple food with enough amounts at rational prices.
Keywords: buffer stocks, price band, stabilization, limited time of supply, staple foods
House Price Volatility and Housing Ownership over the Lifecycle
We develop and test a model on the effects of spatial housing price risk on housing choice. Housing price risk can be substantial but, unlike other risky assets which people can avoid, most people want to eventually own their home thereby creating an insurance demand for housing ownership early in life. With increasing demographic needs over the life cycle, our model predicts that people living in places with higher housing price risk should own their first home at a younger age, should live in larger homes, and should be less likely to refinance. These predictions are shown to hold using comparable panel data from the United States and United Kingdom. (JEL D12, D91
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