Add text-valued <title> element child of <feature> per Maps4HTML/MapM…

…L.js#316.

Change mapml vocabulary to the xhtml namespace.

Fix error in URL introduced in previous commit.

schema/README.md

@@ -1,25 +1,22 @@
 # MapML
 
-[Map Markup Language](http://maps4html.github.io/MapML/spec/) is  'MicroXML' vocabulary for maps. 
+[Map Markup Language](https://maps4html.org/MapML/spec/) is a proposed HTML vocabulary for maps. 
 Although document validity is not a concept that can be strictly enforced on the internet, 
 the documents in this directory are an attempt to provide guidance to map authors on what 
 constitutes markup that is understood as being within scope of the MapML specification.
 
-In principle, a MapML document should be parseable with an HTML-like parser, because
-many of the elements are copied from the HTML vocabulary and are intended to have 
-identical processing semantics to their counterpart in HTML.
+In principle, a MapML document should be parseable the HTML parser, because
+many of the elements are extended from the HTML namespace and are intended to have 
+identical processing semantics to their counterpart in HTML apart from extensions specified in MapML.
 
-In practice, no such MapML parser exists at the time of writing, and it should be good enough to encode
-a MapML document in [MicroXML](https://dvcs.w3.org/hg/microxml/raw-file/tip/spec/microxml.html) syntax so that an XML parser can be used.  When such a parser is used,
+In practice, no such MapML/HTML parser exists at the time of writing, and it should be good enough to encode
+a MapML document in HTML5 XML syntax so that Web browsers' XML parsers can be used.  When such a parser is used,
 it should be possible to use the schema / schematron documents in this directory to validate certain
 rules of MapML documents.  The schemas / schematron files in this directory are intended to 
-evolve as the concept of MapML evolves, and perhaps at some point when enough people
-get involved we will be able to 'fork' the nu validator / parser for HTML to provide a similarly
-robust parsing and validation service online. 
+evolve as the concept of MapML evolves. 
 
 ## Instructions
 
-The files microxml.sch (a single [schematron](http://schematron.com/) validation rule for MicroXML syntax),
 mapml.rnc (a [RelaxNG](http://www.relaxng.org/compact-tutorial-20030326.html) compact syntax schema) and mapml.sch (post-schema validation MapML
 schematron rules) are intended to be applied in that order.
 

schema/mapml.rnc

@@ -1,4 +1,5 @@
 datatypes xsd = "http://www.w3.org/2001/XMLSchema-datatypes" 
+default namespace = "https://www.w3.org/1999/xhtml/"
 start = mapml 
 mapml = element mapml { head?, attribute lang {text}?, body }
 head = element head { headContent }
@@ -78,7 +79,7 @@ feature = element feature {
     attribute id { text }?,
     attribute class { text }?,
     attribute zoom { text }?,
-    (geometry? & properties?)
+    (geometry? & properties? & title?)
 }
 tile = element tile {
     attribute col { xsd:integer },
@@ -89,6 +90,7 @@ bbox = element bbox { twoPositions }
 image =    element image { ImageModel }
 geometry = element geometry { GeometryContent }
 properties = element properties { PropertyContent }
+title = element title { text? }
 
 ImageResourceMetadataAttributes =  
     attribute src { text },