[GitHub] [jena-site] kinow commented on a diff in pull request #139: Update system-initialization.md

[GitBox <gi...@apache.org>]

kinow commented on code in PR #139:
URL: https://github.com/apache/jena-site/pull/139#discussion_r1064026267


##########
source/documentation/notes/system-initialization.md:
##########
@@ -2,54 +2,76 @@
 title: Apache Jena Initialization
 ---
 
-Jena has a simple initialization sequence that is
+Jena has an initialization sequence that is
 used to setup components available at runtime.
 
 Application code is welcome to also use this mechanism. This
-must be done with care. Java initialization can lead to
-visibility of uninitialized data.
+must be done with care. During Jena initialization, there can be 
+visibility of uninitialized data in class static members.
 
 The standard initialization sequence is  
 Core -> RIOT -> ARQ -> TDB -> other (including jena text)
 
-The sequence from core to TDB should be executed before application
-components. See below for how to control the order.
+The sequence from 0 to level 500 is the Jena platform
+initialization. Application may use the jena initialization mechanism and it is
+recommended to place initialzation code above level 500.
 
 Initialization occurs when `JenaSystem.init()` is first called.  Jena ensures that this
 is done when the application first uses any Jena code by using class
 initializers.
 
+Application can call `JenaSystem.init()`. 
+
 See [notes on repacking Jena code](jena-repack.html) for how to deal
-with ServiceLoader files in repacked jars.
+with `ServiceLoader` files in repacked jars.
 
 ## Initialization code
 
-Initialization code is an implementation of `JenaSubsystemLifecycle`.
-For use in the default initialization, the class must have a zero-argument constructor
+Initialization code is an implementation of `JenaSubsystemLifecycle` which
+itself extends `SubsystemLifecycle`.
+
+For use in the default initialization, the class must have a zero-argument
+constructor and implement:
 
+```java
     public interface JenaSubsystemLifecycle {
         public void start() ;
         public void stop() ;
         default public int level() { return 9999 ; }
     }
+```
 
-The code also supply a level, indicating its place in the order of initialization.
+The code should supply a level, indicating its place in the order of initialization.
 The levels used by Jena are:
 
 * 0 - reserved
 * 10 - Used by jena-core
+* 15 - CLI Commands registry
 * 20 - RIOT
 * 30 - ARQ
-* 40 - TDB
-* 9999 - other
+* 40 - Text indexing
+* 40 - TDB1
+* 42 - TDB2
+* 60 - Additional HTTP configuration
+* 60 - RDFPatch
+* 96 - SHACL
+* 96 - ShEx
+* 101 - Fuseki
+* 9999 - Default.
+
+Levels up to 500 are considered to be "Jena system level", Application code
+should use level above 500.
+
+Fuseki initialization includes [Fuseki
+Modules](/documentation/fuseki2/fuseki-modules) which uses `SubsystemLifecycle`
+with a different Java interface.
 
 ## The Initialization Process
 
-The process followed by `JenaSystem.init()` is to obtain an instance of
-`JenaSubsystemRegistry`, ask it to `load()` initialization code, then call
-that code in an order based on declared level. The order of invocation
-of different initialization code within the same level is undefined
-and may be different from run to run.
+The process followed by `JenaSystem.init()` is to load all java `ServiceLoader`
+regsitered `JenaSubsystemLifecycle`, sort into level order, then call `init` on

Review Comment:
   s/regsitered/registered



##########
source/documentation/notes/system-initialization.md:
##########
@@ -2,54 +2,76 @@
 title: Apache Jena Initialization
 ---
 
-Jena has a simple initialization sequence that is
+Jena has an initialization sequence that is
 used to setup components available at runtime.
 
 Application code is welcome to also use this mechanism. This
-must be done with care. Java initialization can lead to
-visibility of uninitialized data.
+must be done with care. During Jena initialization, there can be 
+visibility of uninitialized data in class static members.
 
 The standard initialization sequence is  
 Core -> RIOT -> ARQ -> TDB -> other (including jena text)
 
-The sequence from core to TDB should be executed before application
-components. See below for how to control the order.
+The sequence from 0 to level 500 is the Jena platform
+initialization. Application may use the jena initialization mechanism and it is
+recommended to place initialzation code above level 500.

Review Comment:
   s/initialzation/initialization



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