document collected XSD element research notes

Collected notes include information on:
 * global/local XSD elements
 * qualified/unqualified XSD elements
 * XSD element's target namespace

notes/xsd_elements.rst

@@ -0,0 +1,59 @@
+==========================
+XSD element research notes
+==========================
+:Authors: Jurko Gospodnetiæ
+:Date: 2014-06-29
+
+
+Global/local elements
+---------------------
+
+XSD schema elements are separated into two disjunct groups:
+
+_`global`
+  top-level elements and non-top-level reference elements (such references may
+  only reference top-level elements, whether from the same or another schema)
+
+_`local`
+  non-top-level non-reference elements
+
+
+_`Qualified`/_`unqualified` elements
+------------------------------------
+
+An XSD element is considered qualified if and only if one of the following
+holds:
+
+* it is `global`_
+* its ``form`` attribute is set to ``qualified``
+* its ``form`` attribute is unset and its schema's ``elementFormDefault``
+  attribute is set to ``qualified``
+
+**suds implementation note:** The only allowed ``form`` & ``elementFormDefault``
+attribute values are ``qualified`` & ``unqualified`` but ``suds`` interprets any
+value other than ``qualified`` as ``unqualified``.
+
+
+Element's _`target namespace`
+-----------------------------
+
+An XSD element may have a `target namespace`_ assigned.
+
+If an XSD element has a `target namespace`_ assigned then an XML element
+corresponding to this XSD element must belong to that namespace.
+
+If an XSD element does not have a `target namespace`_ assigned then an XML
+element corresponding to this XSD element must not belong to any namespace.
+
+Whether an XSD element has a `target namespace`_ assigned depends on whether it
+is `qualified`_ or not, whether it is a reference and on its or its referenced
+element schema's ``targetNamespace`` attribute:
+
+* an `unqualified`_ element never has a `target namespace`_ assigned
+* a non-reference `qualified`_ element collects its `target namespace`_ from its
+  schema's non-empty ``targetNamespace`` attribute or has no `target namespace`_
+  if its schema does not have a non-empty ``targetNamespace`` attribute value
+  specified
+* a reference element (such elements are always `qualified`_) collects its
+  `target namespace`_ in the same way but used its referenced element schema
+  instead of its own