Validating XML input

The StreamServer can be instructed to validate the XML input before processing the data. The input can be validated against a DTD or XSD (XML Schema).

Validating against DTDs

The <!DOCTYPE...> tag in the XML input determines which DTD to validate against. For example:

<!DOCTYPE Music SYSTEM "C:\DTDS\musichits.dtd">

Validating against XSDs

You can use an XSD mapping table to determine which XSD to validate against. See XSD mapping table.

You can also use the schema location attributes prefix:noNamespaceSchemaLocation or prefix:schemaLocation in any element. For example:

xsi:schemaLocation="C:\DTDS\musichits.xsd"

The schema location attributes have the namespace URI http://www.w3.org/2001/XMLSchema-instance.

See the W3C XML schema recommendation for more information.

Relative paths to DTDs and XSDs

The path to a DTD or XSD can be relative, for example <!DOCTYPE Music SYSTEM "musichits.dtd"> or xsi:schemaLocation="musichits.xsd". If the XML input is polled using HTTP(S) Poll input connectors, the path is relative to the polled server’s URL. For all other types of input connectors, the path is relative to the Project’s export directory.

Validation levels

There are five levels of validation. To select which level to use, you must:

1	In the Design Center Message window, right-click the XMLIN Event and select Settings. The Event Settings dialog box opens.

2	On the Agent Settings tab, select Validation level and click OK.

 

Validation level
DTD + XSD strict validation	Validate and preprocess incoming XML against a DTD or XSD. This option decreases performance, but prevents the StreamServer from processing XML documents that are not well-formed or valid. When validating against an XSD, a root element that cannot found in any XSD will be treated as an error.
DTD + XSD lax validation	Same as above. The difference is that a root element that cannot found in any XSD will NOT be considered to be an error.
DTD validation	Validate and preprocess incoming XML against a DTD. This option decreases performance, but prevents the StreamServer from processing XML documents that are not well-formed or valid.
Preprocess	The StreamServer will preprocess the XML input. This option slightly decreases performance, but prevents the StreamServer from processing input that is not well formed. Documents that are not valid will be processed.
No validation/preprocessing	The StreamServer will not validate or preprocess the XML input. This option gives the best performance, but does not prevent the StreamServer from processing input that is not well formed or valid.

XSD mapping table

An XSD mapping table contains namespace to schema location mappings.

XSD mapping table description
Table syntax	namespace_URI schema_location load_option
namespace_URI	The namespace URI to map against a schema.
schema_location	The schema location. Relative to the export directory
load_option	Specifies when to load a schema. Can be either 0 or 1. If load_option is not specified, you must use the argument -xsdimport <0|1> to define when to load schemas. 0: The schema will be loaded when input related to the schema is received. The schema is read and parsed before validation. 1: The schema will be loaded at StreamServer start-up. The schema is always available, but occupies memory.

Example 24

XSD mapping table

 

//!multicolumn! http://www.streamserve.com/xsd/schema/one schemaone.xsd 1 http://www.streamserve.com/xsd/schema/two schematwo.xsd 0 http://foo.com ./grb/xsd001.xsd 1

 

If schema locations are specified both in the mapping table and by schema location attributes in the XML document (xsi:schemaLocation etc.), the following apply:

•	If the XSD is loaded at start-up, the mapping table will override the schema location attributes.

•	If the XSD is not loaded at start-up, the schema location attributes will override the mapping table.

Sending error messages

You can create a Message that sends an error message each time a validation error occurs. See Creating an XMLIN validation error Message.