fix a diagram and add alt text

documentation/src/main/asciidoc/introduction/Entities.adoc

@@ -934,16 +934,17 @@ An association between entity classes may be either:
 - _unidirectional_, navigable from `E` to `F` but not from `F` to `E`, or
 - _bidirectional_, and navigable in either direction.
 
-In this diagram, we can see the sorts of associations which are possible.
+In this example data model, we can see the sorts of associations which are possible:
 
-image::images/associations.png[]
+image::images/associations.png[Example data model,align="center",pdfwidth=90%]
 
 [TIP]
 // .One-to-one associations and subtyping
 ====
-An astute observer of the diagram above might notice that the relationships we've represented as unidirectional one-to-one associations could reasonably be represented in Java using subtyping.
+An astute observer of the diagram above might notice that the relationship we've presented as a unidirectional one-to-one association could reasonably be represented in Java using subtyping.
 This is quite normal.
 A one-to-one association is the usual way we implement subtyping in a fully-normalized relational model.
+It's related to the `JOINED` <<mapping-inheritance,inheritance mapping>> strategy.
 ====
 
 There are three annotations for mapping associations: `@ManyToOne`, `@OneToMany`, and `@ManyToMany`.

documentation/src/main/asciidoc/introduction/Interacting.adoc

@@ -48,7 +48,7 @@ Thus, an entity instance may be in one of three states with respect to a given p
 2. _persistent_ — currently associated with the persistence context, or
 3. _detached_ — previously persistent in another session, but not currently associated with _this_ persistence context.
 
-image:images/entity-lifecyle.png[width=800,align="center"]
+image::images/entity-lifecyle.png[Entity lifecycle,width=800,align="center"]
 
 At any given moment, an instance may be associated with at most one persistence context.
 

documentation/src/main/asciidoc/introduction/Introduction.adoc

@@ -57,7 +57,7 @@ We can think of the API of Hibernate in terms of three basic elements:
 - a _native API_ exposing the full set of available functionality, centered around the interfaces `SessionFactory`, which extends `EntityManagerFactory`, and `Session`, which extends `EntityManager`, and
 - a set of _mapping annotations_ which augment the O/R mapping annotations defined by JPA, and which may be used with the JPA-defined interfaces, or with the native API.
 
-image::images/api-overview.png[width=700,align="center"]
+image::images/api-overview.png[API overview,width=700,align="center"]
 
 As an application developer, you must decide whether to:
 

documentation/src/main/asciidoc/introduction/Tuning.adoc

@@ -108,7 +108,7 @@ fundamental rule of thumb in ORM is:
 of a session/transaction, and fetch it immediately in one or two queries,
 - and only then start navigating associations between persistent entities.
 
-image:images/fetching.png[width=700,align="center"]
+image::images/fetching.png[Fetching process,width=700,align="center"]
 
 Without question, the most common cause of poorly-performing data access
 code in Java programs is the problem of _N+1 selects_. Here, a list of N