Map Layer

Map layers are an abstraction that is implemented by the Web-Map-Custom-Element library as HTML primitives (elements).  <br/><br/>Map content comes in various types, or flavours, including images, image tiles, vector features and vector tiles.  <br/><br/>The intention of the MapML specification is to represent all these types as elements, adding new elements to the HTML vocabulary where necessary.<br/><br/>MapML will specify a #lt;layer#gt; element which will enable network-based (fetch) access to map content, or inline DOM content as MapML/HTML.<br/><br/><u>Background</u><br/><br/>HTML stands for "Hyper Text Markup Language", and as such, hypertext represents the fundamental media type of the Web, allowing, as it does, the linking of content together in a way that partitions the infoshpere into manageable chunks collectively and abstractly known as "resources".<br/><br/>Resources are a fundamental abstraction of the Web, and they are addressable by Uniform Resource Locators, or URLs, which are Web "addresses".  Hypertext allows documents to embed these Web addresses in a way that enables browsers and crawlers to load resource "representations" either embedded inline (e.g. #lt;img src="..."#gt;) or as separate documents for direct presentation to the user (e.g. #lt;a href="..."#gt;my other doc#lt;/a#gt;).<br/><br/>A map layer is an abstract resource that only has meaning in the coordinate system context of a map.  Its representation may be loaded via a URL encoded in hypertext, or layer content may be included inline in the host document. In the former case, no DOM access beyond the layer interface itself is anticipated; in other words, in this instance the layer will be a content container with program access to the container only.  When layer content is represented inline, as MapML markup (part of HTML), DOM access and programmability of all MapML / HTML content is anticipated and in scope for this specification.<br/>