NAME
XML::RelaxNG::Compact::DataModel - RelaxNG Compact http://relaxng.org/compact-tutorial-20030326.html schema expressed in perl
VERSION
Version 0.15
DESCRIPTION
This is a user's guide module for documentation only. It describes the perlish expression of the RelaxNG Compact schema. Some limitations are (please see RelaxNG standard for reference):
there is no datatyping,
there is no support for minLength,maxLength xsd:string constraints, although conditional logic is supported
there is no support for annotations
support for includes and
inheritare provided by the data model developer, means you can split your model in different packages and inherit it. Just remember that PXB object model is based on references to hashes and arrays. See below.
Everything else can be expressed by perl constructs and will be supported by the created data binding API. Every element from the schema can be expressed as perl hash reference:
<element-variable> = '{ attrs => {' <attributes-definition> ', '
'xmlns => ' <namespace-prefix> '},'
'elements => [' <elements-definition> '],'
'text =>' <text-content> ','
'sql => {' <sql-mapping-definition or any other mapping to external data model> '}'
'}' Where each <xxxx-definition> can be expressed in EBNF as:
<attributes-definition> = (attribute-name '=>' attribute-value) ( ',' <attributes-definition>)*
attribute-name = string
namespace-id = string
attribute-value = 'scalar' | ('enum:'(attribute-name ( ',' attribute-name)*))
<elements-definition> = ( '[' element-name '=>' (
<element-variable> |
’'[' ‘ <element-variable> '’]’' |
’'[‘' ( <element-variable> '’,'’)+’ ']’' |
'’[‘' ('['‘ <element-variable> '’]’,'’?)+ ’']'’ )
',' conditional-statement? ']’')*
conditional-statement = ('unless'|'if')':'(registered-name (',' registered-name)*)
registered-name = attribute-name|element-name
element-name = string
<text-content> = 'scalar'|conditional-statement
<sql-mapping-definition> = (sql-table-name '=> {' sql-table-entry '}' ) ( ',' <sql-mapping-definition>)*
sql-table-entry = (sql-entry-name '=> {' entry-mapping '}' ) ( ',' sql-table-entry )*
sql-table-name = string
sql-entry-name = string
entry-mapping = 'value' '=>'( element-name|( '[' element-name (',' element-name)+ ']')) ( ',' if-condition)?
if-condition = 'if => ( ' attribute-name ':' attribute-value | '[' (' attribute-name ':' attribute-value ',' )+ ']' )In the attributes definition the xmlns attribute is reserved for the namespace prefix. This name must be registered within Namespace class in order to provide some level of validation. This constraint will be fixed in future releases. Its recommended to have unique id attribute in each element, it will allow to utilize mapping by id for the complex element types.
There is some conditional logic allowed for attributes. An attribute value can be scalar which stays for scalar string or enumerated list of the allowed names. The list of elements is represented as array reference. The choice between several possible elements is introduced as array reference to the list and having multiple elements of one kind is represented as reference to array consisted with single element variable of that kind.
For example:
-
elements => [parameter => $parameter] - defines single "parameter" sub-element -
elements => [parameter => [$parameter]] - defines list of "parameter" sub-elements -
elements => [parameters => [$parameters, $select_parameters]] - defines choice between two single "parameters" sub-elements of different type -
elements => [datum => [[$pinger_datum],[$result_datum]] ] - defines choice between two lists of "datum" sub-elements of different type
In elements-definition the third member is an optional conditional statement which represents validation rule. For example unless:value conditional statement will be translated into the perl's conditional statement && !($self->value) where value must be registered attribute or sub-element name and this condition will be placed in every piece of code where perl object is serialized into the XML DOM object or from it.
SYNOPSIS
## for example lets define some RelaxNG schema in Compact notation and then express it as perl data structures
# this is a base schema from the L<http://ogf.org/schema/network/topology/base> namespace
#
# start =
# (
# element nmwg:message {
# MessageContent
# }
# )
#
# MessageContent =
# Identifier? &
# MessageIdentifierRef? &
# Type &
# Parameters? &
# (
# Metadata
# )+
#
# Identifier = attribute id { xsd:string }
#
# IdReference = attribute idRef { xsd:string }
#
# Type = attribute type { xsd:string }
# MetadataIdentifierRef = attribute metadataIdRef { xsd:string }
#
# MessageIdentifierRef = attribute messageIdRef { xsd:string }
#
# Metadata =
# element nmwg:metadata {
# (
# Identifier &
# MetadataIdentifierRef? &
# MetadataContent
# )
# }
#
# MetadataBlock =
# Parameters?
#
# MetadataContent =
# (
# MetadataBlock
# ) &
# EventType? &
#
# EventType = element nmwg:eventType { xsd:string }
#
# Parameters =
# element nmwg:parameters {
# ParametersContent
# }
#
# ParametersContent =
# Identifier &
# Parameter+
#
# Parameter = element nmwg:parameter {
# attribute name {
# "count" | "packetInterval" | "endTime"|
# "packetSize" | "ttl" | "startTime" |
# "valueUnits"
# } &
# (
# attribute value { text } |
# text
# )
# }
#----------------------------------------------------------------------------
# Lets start from the bottom of our schema
#
# "parameter" element is the most elemental one
# it has no sub-elements , handful of attributes and text content which is set only if value attribute is not
$parameter = {attrs => {name => 'enum:count,packetInterval,packetSize,ttl,valueUnits,startTime,endTime',
value => 'scalar',
xmlns => 'nmwg'},
elements => [],
text => 'unless:value',
};
#
# the first complex element with more than one "parameter" sub-element
#
$parameters = {attrs => {id => 'scalar',
xmlns => 'nmwg'},
elements => [
[parameter => [$parameter]],
],
};
#
# another layer of comlexity with added evetType sub-element, since this is a text content only element then
# there is no need to define it separately
#
$metadata = {attrs => {id => 'scalar', metadataIdRef => 'scalar',
xmlns => 'nmwg'},
elements => [
[parameters => $parameters],
[eventType => 'text']
],
};
#
# this is the top most element of the schema
#
$message = {attrs => {id => 'scalar', type => 'scalar', xmlns => 'nmwg'},
elements => [
[parameters => [$parameters]],
[metadata => [$metadata]],
[data => [$data]]
],
};
## this is it, as you can see it takes even less code to express the same RelaxNG compact schema
## and of course that means even less code in case of XML schema
# more elaborate examples could be found below
SQL MAPPING
After ( or at the time of ) defining your elements you can set your sql mapping. Actually, it could be mapping to any external data model. Lets see how we can map parameters from parameter element into some fields from some SQL DB table
# take C<$parameter> element from the previous example $parameter->{sql} =
# for example this statement will map 'count' field of the metadata table to be populated
# from attribute 'value' or text when attribute 'name' == 'count'
#
# actually it will return this structure:
# metaData => { count => <value> }
#
#
{metaData => {count => { value => ['value' , 'text'], if => 'name:count'},
packetInterval=> { value => ['value' , 'text'], if => 'name:packetInterval'},
packetSize=> { value => ['value' , 'text'] , if => 'name:packetSize'},
ttl=> { value => ['value' , 'text'] , if => 'name:ttl'},
protocol => { value => ['value' , 'text'] , if => 'name:protocol'},
transport => { value => ['value' , 'text'] , if => 'name:transport'},
},
# next statement will define where to get time range and will return it as 'time' range data structure
# for example: time => { 'ge' => '111111111', 'le' => '222222222' }
#
# that means you absolutely free on how to use this mapping
time => { 'ge' => { value => ['value' , 'text'], if => 'name:startTime'},
'le' => { value => ['value' , 'text'], if => 'name:endTime'},
},
}; DEVELOPING DATA MODELS
The best design pattern would be consisted of writing your data model by following your schema design. Create DataModel.pm package for the base schema and export all necessary data structures and then somewhere in the building script add any extra sql mapping or even redefine some elements by replacing particular element definitions with new data structure. Of course you can mix elements with the same names from the different namespaces, just name them differently but it would be easier to define them in separate data model packages.
Note: You have to define element bottom-to-top in order for them to "know" about each other. The most common design pattern here is to define your base schema with some strategically placed schema extending containers. For example:
package MyBase;
use strict;
use warnings;
use Exporter ();
use base qw/Exporter/;
our @EXPORT_OK = qw/$extended $base_parameter $parameters/;
our($base_parameter, $parameters);
$base_parameter = {attrs => {name => 'enum:name1,name2', value => 'scalar', xmlns => 'nsid'},
elements => [],
text => 'unless:value',
};
# addExtra is closure based callback, intialized with $base_parameter
sub addExtra {
my $extras = [[$base_parameter]];
return sub {
push @{$extras}, [@_] if @_;
return $extras
}
}
# define $parameters with $extended placeholder for adding extra variations of the parameter
our $extended = addExtra();
$parameters = {attrs => { xmlns => 'nsid'},
elements => [
parameter => $extended->()],
],
};
package ExtendedBase1;
use strict;
use warnings;
use Exporter ();
use base qw/Exporter MyBase/;
our @EXPORT_OK = qw/$extended $parameters/;
### notice different namespace, if you set the same one it will overwrite the former one.
$extended->({attrs => {ext_name => 'scalar', ext_value => 'scalar', xmlns => 'nsid1'},
elements => [],
text => 'unless:ext_value',
});
package ExtendedBase2;
use strict;
use warnings;
use Exporter ();
use base qw/Exporter ExtendedBase1/;
our @EXPORT_OK = qw/$extended $parameters/;
### notice different namespace, if you set the same one it will overwrite the former one.
$extended->({ attrs => {another_name => 'scalar', another_value => 'scalar', xmlns => 'nsid2'},
elements => [],
text => 'unless:another_value',
});
package main;
use strict;
use warnings;
use Data::Dumper;
use POD::Credentials;
use XML::RelaxNG::Compact::PXB;
use base qw/ExtendedBase2/;
## adding some sql mapping for base_parameter
$base_parameter->{sql} = { tableName => { field1 => { value => ['value' , 'text'],
if => 'name:name1'
},
field2 => { value => ['value' , 'text'],
if => 'name:name2'},
}
};
#
# creating API
#
my $api_builder = XML::RelaxNG::Compact::PXB->new({
top_dir => './',
datatypes_root => "XMLTypes",
project_dir => 'MyAPI',
nsregistry => { 'nsid1' => 'http://some.org/nsURI'},
schema_version => '1.0',
test_dir => 't',
footer => POD::Credentials->new({author=> 'Joe Doe'}),
});
$api_builder->buildAPI({name => 'myParameters', element => $parameters});
1;
AUTHOR
Maxim Grigoriev, maxim at fnal_gov
LICENSE
Fermitools license (open source, modified BSD type), see http://fermitools.fnal.gov/about/terms.html
COPYRIGHT
Copyright (C) 2007-2011 by Fermitools, Fermilab
1 POD Error
The following errors were encountered while parsing the POD:
- Around line 66:
Non-ASCII character seen before =encoding in '’'[''. Assuming CP1252