docs: complete paragraph on meta information

Author: lonvia

docs/user_manual/01-First-Steps.md

@@ -140,7 +140,7 @@ out about the tags. It is also always useful to consult
 different keys and value in actual use.
 
 Tags are common to all OSM objects. After that there are three kinds of
-objects in OSM: nodes, ways and relations.
+object types in OSM: nodes, ways and relations.
 
 ### Nodes
 
@@ -187,7 +187,7 @@ backward references when talking about the dependencies between objects:
 
 * A __forward reference__ means that an object is referenced to by another.
   Nodes appear in ways. Ways appear in relations. And a node may even have
-  an indirect forward reference to a relation through a way it appear in.
+  an indirect forward reference to a relation through a way it appears in.
   Forward references are important when tracking changes. When the location
   of a node changes, then all its forward references have to be reevaluated.
 
@@ -198,6 +198,10 @@ backward references when talking about the dependencies between objects:
   to follow the backward references for ways and relations until we reach
   the nodes.
 
+Closely related to backward references is the concept of __reference
+completeness__. A dataset or file is considered reference complete when
+all backward references can be resolved.
+
 ## Order in OSM files
 
 OSM files usually follow a sorting convention to make life easier for

docs/user_manual/02-Extracting-Object-Data.md

@@ -14,7 +14,8 @@ Finally, there is a type for changesets, which contains information about
 edits in the OSM database. It can only appear in special changeset files
 and explained in more detail [below](#changeset).
 
-The FileProcessor may return any of these objects, when iterating over a file.
+When iterating over a file, then the FileProcessor may return any of these
+objects.
 Therefore, a script will usually first need to determine the type of object
 received. There are a couple of ways to do this.
 
@@ -83,7 +84,7 @@ You can simply test for this object type:
 ## Reading object tags
 
 Every object has a list of properties, the tags. They can be accessed through
-the `tags` property, which provides a simple dictionary-like view of the tags.
+the `tags` property. It provides a simple dictionary-like view of the tags.
 You can use the bracket notation to access a specific tag or use the more
 explicit `get()` function. Just like for Python dictionaries, an access by
 bracket raises a `ValueError` when the key you are looking for does not exist,
@@ -140,7 +141,23 @@ list into a Python dictionary:
 ## Other common meta information
 
 Next to the tags, every OSM object also carries some meta information
-describing its ID, version and information regarding the editor.
+which all can be accessed through read-only properties.
+
+The most important meta information is the object's ID in the `id` property.
+This is the ID used when object reference each other.
+
+The other meta information mostly relates when and by whom it was edited.
+The following table gives a quick overview over the properties:
+
+| Property  | Description |
+|-----------|--------------------------|
+| version   | Version of the object. A newly created object starts with version 1. |
+| deleted   | A boolean property saying if the object should be used or ignored. Only relevant for [change](08-Working-With-Change-Files.md) and [history](09-Working-With-History-Files.md) files. |
+| changeset | The ID of the change set this object was created with. A change set contains a set of edits that have been uploaded by an editor in a single session. |
+| timestamp | UTC time at which the object was created, or more precisely, added into the database. |
+| uid       | The ID of the user who created this version of the object. User IDs are univocal and prepetual. |
+| user      | The name of the user who created this version of the object. This is the name the user had when the object was created. User names may be changed over time. The same name in different objects doesn't necessarily mean that the change was made by the same user. |
+
 
 ## Properties of OSM object types