add validation

adr-provs/ddd-validation.md

@@ -0,0 +1,24 @@
+# ddd-validation
+
+## Status
+
+to be discussed
+
+## Context
+
+We want express validity on domain objects. Clear described validity helps on 
+* avoid many redundant and unnecessary (null-)checks spread around in the code
+* collects all validity constraints to one defined place
+
+### Principles affected
+
+* Check the domain borders
+* Do not tie validation to object creation / serialization
+* propagate validation through aggregates
+
+![ddd-validation](ddd-validation.png)
+
+### see also:
+* [Fowler] Do not use exceptions for validation: https://martinfowler.com/articles/replaceThrowWithNotification.html
+* [Fowler] Contextual Validation: https://martinfowler.com/bliki/ContextualValidation.html
+* [Vladimir Khorikov] Some ideas for validation in DDD: https://enterprisecraftsmanship.com/posts/validation-and-ddd/

adr-provs/partial-execution.md

@@ -25,5 +25,3 @@ We want to be able to execute single provision steps to apply partial installati
   * Vorbehalt2: entscheiden, was in der domain testbar sein muss
 
 * Wir nutzen nur einschichtige Konfiguration, da wir nur noch uns selbst als Nutzerkreis ansehen.
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