Ensemble Virtual Documents
Controlling Message Validation
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For virtual documents other than ASTM documents, Ensemble can provide message validation, with an option to include a business host to handle bad messages. You can also override the validation logic, if wanted. This chapter describes the details. It includes the following topics:

Introduction to Message Validation
For virtual documents other than ASTM documents, one or more of the specialized business host classes include the Validation setting, which you use to specify how that business host should validate messages that it receives, before attempting further work.
If the message does not fail validation, the business host sends the message to the specified normal target or targets.
If the document does fail validation, the details are different depending on the kind of business host:
Basic Validation Options and Logic
This topic describes the allowed values for the Validation setting and describes how Ensemble validates a message. (Note that HL7 Version 2 has an additional flag related to Z-segments and has additional logic; see the Ensemble HL7 Version 2 Development Guide.)
Value Meaning
d Validation examines the DocType property of the document to see if it has a value.
m Validation verifies that the document segment structure is well formed, and that it can be parsed using the schema identified in the DocType property of the document.
dm For most virtual document formats, this is the default setting. Both d and m are active.
1 Same as dm, for backward compatibility with previous releases.
(a blank string) The routing process skips validation and routes all documents as given in the associated routing rule set.
The d Validation Flag
If the d flag is present in the Validation string, Ensemble examines the Schema Category specified in the message (as set by the business service) and compares it with the message DocType. If the Schema Category in the message is blank, the message is automatically declared bad. However, if Schema Category is not blank, but does not match the message DocType, validation can continue, as long as there are more Validation flags defined, such as m.
The m Validation Flag
If the m flag is present in the Validation string, Ensemble searches for a way to either validate the message, or declare it bad The details depend upon the virtual document type.
Overriding the Validation Logic
The virtual document routing process (EnsLib.MsgRouter.VDocRoutingEngine), and its subclasses provide default validation logic. Most of the specialized virtual document business service and operation classes also provide validation logic. You can override the validation logic; to do so, create and use a subclass of the applicable class.
Overriding the Validation Logic in a Routing Process Class
If you create a subclass of an Ensemble class and then override the OnValidate() method, you can:
When you override the OnValidate() method, you may also override the Validation property definition in the same subclass. Pay careful attention to the following details:
Overriding the Validation Logic in a Business Service or Operation Class
The virtual document business service and operation classes each provide a Validation property and OnValidate() method that you can override. By default, this property is not exposed as a setting for any of these business services or business operations, and by default, no OnValidate() activity ever occurs in these classes. You can change this if you want to validate documents at the incoming or outgoing sides of the interface, rather than at the routing engine as is the usual case. To accomplish this, follow these steps:
  1. Use the instructions for overriding Validation and OnValidate() provided above.
  2. If you want your users to be able to choose a type of validation, also add the Validation property as a setting. See Adding and Removing Settings in Developing Ensemble Productions.
Defining Bad Message Handlers
A routing process has the setting Bad Message Handler. The purpose of this setting is to indicate the business host to which the process should send messages that are found to be bad, according to the Bad Message Handler of the business process. To define a bad message handler, first decide how you want to handle the bad message. Typically you create a business operation. This business operation could do either or both the following, for example:
Note that the business process sends the bad message to this business host instead of its usual target for validated messages.
If a message is bad and if the Bad Message Handler setting is not specified, the routing process simply stops the validation sequence and does not send the message.

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