README.md in aixm-0.1.3 vs README.md in aixm-0.2.0

@@ -29,17 +29,17 @@
 
 You can initialize all elements either traditionally or by use of shorter
 AIXM class methods:
 
 ```ruby
-AIXM::Feature::Airspace.new(...)
 AIXM.airspace(...)
+AIXM.airspace(...)
 ```
 
 ### Fundamentals
 
-All fundamentals are bundled at the root of the module `AIXM`.
+All fundamentals are subclasses of `AIXM::Base`.
 
 ### Document
 
 The document is the root container of the AIXM snapshot file to be generated.
 It's essentially a collection of features:
@@ -75,18 +75,24 @@
 #### Altitude and Heights
 
 Altitudes and heights exist in three different forms:
 
 ```ruby
-AIXM.z(alt: 1000, code: :QFE)   # height: 1000ft above ground
-AIXM.z(alt: 2000, code: :QNH)   # altitude: of 2000ft above mean sea level
-AIXM.z(alt: 45, code: :QNE)     # altitude: flight level 45
+AIXM.z(1000, :qfe)   # height: 1000ft above ground
+AIXM.z(2000, :qnh)   # altitude: of 2000ft above mean sea level
+AIXM.z(45, :qne)     # altitude: flight level 45
 ```
 
+#### Frequency
+
+```ruby
+AIXM.f(123.35, :mhz)
+```
+
 ### Features
 
-All features are subclasses of `AIXM::Feature`.
+All features are subclasses of `AIXM::Feature::Base`.
 
 #### Airspace
 
 * AIXM.airspace
   * name: String
@@ -95,13 +101,76 @@
   * schedule = AIXM.schedule
   * geometry << AIXM.point, AIXM.arc, AIXM.border or AIXM.circle
   * class_layers << AIXM.class_layer
   * remarks = String
 
+#### Navigational Aids
+
+##### Designated Point
+
+* AIXM.designated_point
+  * id: String
+  * name: String
+  * xy: AIXM.xy
+  * z: AIXM.z or *nil*
+  * type: :icao, :adhp, :coordinates or :other
+  * remarks = String
+
+##### DME
+
+* AIXM.dme
+  * id: String
+  * name: String
+  * xy: AIXM.xy
+  * z: AIXM.z or *nil*
+  * channel: String
+  * remarks = String
+
+##### NDB
+
+* AIXM.ndb
+  * id: String
+  * name: String
+  * xy: AIXM.xy
+  * z: AIXM.z or *nil*
+  * f: AIXM.f
+  * remarks = String
+
+##### Marker
+
+* AIXM.marker
+  * id: String
+  * name: String
+  * xy: AIXM.xy
+  * z: AIXM.z or *nil*
+  * remarks = String
+
+##### TACAN
+
+* AIXM.tacan
+  * id: String
+  * name: String
+  * xy: AIXM.xy
+  * z: AIXM.z or *nil*
+  * channel: String
+  * remarks = String
+
+##### VOR and DVOR
+
+* AIXM.vor
+  * id: String
+  * name: String
+  * xy: AIXM.xy
+  * z: AIXM.z or *nil*
+  * type: :vor or :vordme
+  * f: AIXM.f
+  * north: :geographic or :magnetic
+  * remarks = String
+
 ### Components
 
-All components are subclasses of `AIXM::Component`.
+All components are subclasses of `AIXM::Component::Base`.
 
 #### Schedule
 
 * AIXM.schedule
   * code: String or Symbol
@@ -146,20 +215,25 @@
 * at least three points, arcs or borders (the last of which a point with
   identical coordinates as the first)
 
 ## Validation
 
-* Use `AIXM::Document#complete?` to check whether all mandatory information is
+Use `AIXM::Document#complete?` to check whether all mandatory information is
 present. Airspaces, geometries etc have `complete?` methods as well.
-* Use `AIXM::Document#valid?` to validate the resulting AIXM against the XSD
-schema. If any, you find the errors in `AIXM::Document#errors`.
 
+Use `AIXM::Document#valid?` to validate the resulting AIXM against the XSD
+schema. If any, you find the errors in `AIXM::Document#errors`. Since the data
+model is not fully implemented, some associations cannot be assigned and have
+to be left empty. The resulting validation errors are silently ignored:
+
+* OrgUid - organizations may be empty tags
+
 ## Rendering
 
 ```ruby
 document.to_xml         # render AIXM 4.5 compliant XML
-document.to_xml(:OFM)   # render AIXM 4.5 + OFM extensions XML
+document.to_xml(:ofm)   # render AIXM 4.5 + OFM extensions XML
 ```
 
 ## Constants
 
 * `AIXM::GROUND` - height: 0ft above ground
@@ -168,17 +242,21 @@
 
 ## Refinements
 
 By `using AIXM::Refinements` you get the following general purpose methods:
 
+* `Hash#lookup(key, default)`<br>Similar to `fetch` but falls back to values
 * `String#indent(number)`<br>Indent every line of a string with *number* spaces
 * `String#uptrans`<br>upcase and transliterate to match the reduced character set for names
 * `String#to_dd`<br>Convert DMS angle to DD or `nil` if the format is not recognized
 * `Float#to_dms(padding)`<br>Convert DD angle to DMS with the degrees zero padded to *padding* length
 * `Float#trim`<br>Convert whole numbers to Integer and leave all other untouched
 * `Float#to_km(from: unit)`<br>Convert a distance from *unit* (:km, :m, :nm or :ft) to km
 
+See the [source code](https://github.com/svoop/aixm/blob/master/lib/aixm/refinements.rb)
+for more explicit descriptions and examples.
+
 ## Extensions
 
 ### OFM
 
 This extension adds proprietary tags and attributes (most of which are prefixed
@@ -192,9 +270,11 @@
 
 ## References
 
 * [AIXM](http://aixm.aero)
 * [AIXM on Wikipedia](https://en.wikipedia.org/wiki/AIXM)
+* [AIXM 4.5 Specification](http://aixm.aero/document/aixm-45-specification)
+* [AICM 4.5 Entity-Relationship](https://www.ead.eurocontrol.int/SystemHelp/mergedProjects/SDO/aixm/)
 * [Open Flightmaps](https://openflightmaps.org)
 
 ## Tests
 
 Some tests are very time consuming and therefore skipped by default. To run the