【正文】 at XML does not have a fixed set of tags and elements that cover the needs of every application or user. Markup in an XML document describes the structure of the document along with the document’s semantics. XML allows the developers to define properly the elements required and to encode their associations. XML defines the syntax that markup languages of each knowledge domain, such as MusicML, MathML, GML and SVG must follow. Although it is quite flexible in the elements’ definition, it is rather strict in many other aspects. It provides grammar rules for the XML documents describing their proper structure, which allows for the development of XML parsers that can read any XML document. Documents that satisfy this grammar are considered as well formed (Elliotte and Means, 2021). . Geography markup language—GML GML is a markup language used to encode and integrate spatial information, spatial relationships and nonspatial information, especially when nonspatial data are XMLencoded. GML also aims to serve both data transport and data storage, in a widearea Inter context. GML exploits W3C standards to encode geographic information that can be readily shared in the Inter. In addition, GML provides a set of mon geographic modeling objects to enable interoperability of independently developed applications. It is designed to support interoperability and does so by providing basic geometry tags, a mon data model and a mechanism for creating and sharing application schemas. Although it is not the first metalanguage introduced to describe geographic information, it is the first that has been widely accepted by the GIS munity. An important characteristic of GML inherited from the XML specification is that it separates spatial and nonspatial content from presentation (Galdos, 2021). . Scalable vector graphics—SVG SVG stands for Scalable Vector Graphics, an XML grammar for stylable graphics used as an XML namespace. SVG is a language for the description of twodimensional graphics in XML and allows for the encoding of three types of objects: vector graphics, images and text. Graphic objects can be grouped, styled, transformed and posed into previously rendered objects. The feature set includes nested transformations, clipping paths, alpha masks, filter effects and template objects, which are applied during rendering. In general, SVG drawings can be interactive and dynamic. Animations can be defined and triggered either declaratively or via scripting (Ferraiolo, 2021). SVG graphics are scalable to different display resolutions. The same SVG graphic can be displayed at different sizes on the same Web page and reused at different sizes on different pages. SVG graphics are scalable because the same SVG content can be a standalone graphic or can be referenced or included in other SVG graphics, thereby allowing a plex illustration to be built up in parts, perhaps by several people. During rendering SVG also provides clientside raster filter effects so that moving to a vector format does not result to the loss of popular effects such as soft drop shadows (Ferraiolo, 2021). Other characteristics of SVG include a smaller file size and searchable text information. An SVG file—utilizing the elements provided by the specification—is usually smaller than a raster file for the same map resolution and thus can be transferred across the Inter more quickly. Text information inside SVG is still text and can be searchable, while text information inside the raster file bees integrated into the image and is no longer recognized as text. SVG is also particularly suitable for displaying intelligent maps, because geometric objects such as points, lines, and polygons are recognized as such and are identifiable. Raster images on the other hand contain information about every pixel, and points, lines and polygons that are no longer recognizable. Therefore, the user can directly work with spatial features on an SVG but not on a raster graphic image (Peng and Zhang, 2021). SVG is also based on XML and therefore conforms to other XMLbased standards and technologies, such as XML Namespace, XLink, and XPointer. XLink and XPointer allow for linking from within SVG files to other files on the Web, like a GML data element, HTML pages or other SVG files (Boye, 1999). . Extensible stylesheet language transformation—XSLT XSLT is a language that enables the user to convert XML documents into other XML documents or into almost any form an application or a user needs. XSLT provides an easy, W3C sanctioned, way to convert XML documents that conform to a schema into documents that conform to another, enabling the sharing of information between different systems. From another perspective XSLT is a programming language that describes the way and the methods to be followed for the transformation of a wellformed tree structure of an XML document to another. XSLT is not the only way to achieve these goals。 there are alternative ways to transform XML documents but XSLT has prevailed. The fact that XSLT is a W3C standard implies that XSLT plies with the specifications published by the W3C or those that will be announced in the future (Clark, 1999). Furthermore, the nonproprietary status of the specification and the platform independency, guarantee the prospects and the integrity of the specification. In addition, the fact that the XSLT document transformation instructions are stored as an XML document is an advantage since there is no need for using another syntax. The abovementioned characteristics justify the popularity of XSLT when it es to XML transformation (DuCharme, 2021). . Data model encoding The accurate representation of the plexity of the real world has been one of the fundamental problems in Geoma