A Low-Overhead Script Language for Tiny Networked Embedded Systems

With sensor networks starting to get mainstream acceptance, programmability is of increasing importance. Customers and field engineers will need to reprogram existing deployments and software developers will need to test and debug software in network testbeds. Script languages, which are a popular mechanism for reprogramming in general-purpose computing, have not been considered for wireless sensor networks because of the perceived overhead of interpreting a script language on tiny sensor nodes. In this paper we show that a structured script language is both feasible and efficient for programming tiny sensor nodes. We present a structured script language, SCript, and develop an interpreter for the language. To reduce program distribution energy the SCript interpreter stores a tokenized representation of the scripts which is distributed through the wireless network. The ROM and RAM footprint of the interpreter is similar to that of existing virtual machines for sensor networks. We show that the interpretation overhead of our language is on par with that of existing virtual machines. Thus script languages, previously considered as too expensive for tiny sensor nodes, are a viable alternative to virtual machines

S-COL: A Copernican turn for the development of flexibly reusable collaboration scripts

Collaboration scripts are usually implemented as parts of a particular collaborative-learning platform. Therefore, scripts of demonstrated effectiveness are hardly used with learning platforms at other sites, and replication studies are rare. The approach of a platform-independent description language for scripts that allows for easy implementation of the same script on different platforms has not succeeded yet in making the transfer of scripts feasible. We present an alternative solution that treats the problem as a special case of providing support on top of diverse Web pages: In this case, the challenge is to trigger support based on the recognition of a Web page as belonging to a specific type of functionally equivalent pages such as the search query form or the results page of a search engine. The solution suggested has been implemented by means of a tool called S-COL (Scripting for Collaborative Online Learning) and allows for the sustainable development of scripts and scaffolds that can be used with a broad variety of content and platforms. The tool’s functions are described. In order to demonstrate the feasibility and ease of script reuse with S-COL, we describe the flexible re-implementation of a collaboration script for argumentation in S-COL and its adaptation to different learning platforms. To demonstrate that a collaboration script implemented in S-COL can actually foster learning, an empirical study about the effects of a specific script for collaborative online search on learning activities is presented. The further potentials and the limitations of the S-COL approach are discussed

Using SVG and XSLT for graphic representation

Using SVG and XSLT for graphic representation In this paper we will present an XML based framework that can be used to produce graphical visualisation of scientific data. The approach rather than producing ordinary histogram and function diagaram graphs, tries to represent the information in a more graphical appealing and easy to understand way. For examples the approach will give the ability to represent the temperature as the level of coulored fluid in a thermometer. The proposed framework is able to maintain the value of the datas strictly separated from the visual form of its representation (positions of element, colours, visual representation etc.). By defining appropriate data structures and expressing them using XML, the framework gives the user the ability to create graphic representations using standard SVG and XSLT. Since XML can be used for describing complex data information, we represent every level of the graphic representation with an XML structure. To describe our architecture we defined the following XML dialects, each one with different markup tags, reflecting the semantical values of the elements. Data definition level. Used to define the value of the datas that can be used in the graphic representation Data representation level. Used to define the graphic representation, it defines how the values expressed by the data definition level are represented. Both data representation and data definition files are based on a DTD to impose the constraints. Data representation level is the core of the system, and defines a powerful language for representation. Source primitives. Used to define for the source of the graphic elements, for example static file or SVG code. Modification primitives. Used to define the modifications that can affect a graphic element, for example rotation, scaling or repetition. Disposition primitives. Used to define the possible dispositions along x, y and z axes, for example to impose a order in the representation of elements. Action primitives. Used to define the possible actions that canbe activated by graphic elements for different user behaviours. For example a mouse action can activate a link to a different resource, or can change the value of any of the other primitives of the data structure, as image source or disposition, or can show a tooltip . XSLT is used to output a SVG file derived from the two files describing the graphic representation. Our aim is to provide an abstract language to be used to represent in different ways the same concept. In fact, we can link a data definition file with different data representation levels, providing different kinds and levels of complexity for the same concept. An example use could be the representation of the temperature described before, where the temperature itself could be represented either as the level of mercury in the termomether, or as the rotation of an arrow in a gauge. The transformation process is made from an XML source tree into an XML result tree, using XPath to define patterns. XSLT transformation process is based on templates, that define some actions (like adding or removing elements, or sorting them) to be performed when a part of the document matches a template. To implement some of the complex graphics operations we are using XSLT extensions that allow to perform mathematical operations. These XSLT extensions are not yet standard and require specific compliant parser, as Apache Xalan, that allows the developer to interface with Java classes in order to increase XSLT areas of application, from simple node transformations to quite complex operations