My Four
Preferences

My Four
Preferences
in my Perl Web practice

Architecture and music

Danube

My Four
Preferences
in my Perl Web practice

1. Parsing URLs with grammar
2. .ini configuration files
3. WWW::Page
4. XSLT

0.
Perl 5.10

1.
Parsing URLs with grammar

URL is . . .

URL is . . .
a string

URL is . . .
a string,
a set of parts

URL is . . .
a string,
a set of parts,
a container of parameters

Blog URL scheme

Blog URL scheme
/

Blog URL scheme
/
/message‐uri/

Blog URL scheme
/
/message‐uri/
/tag/tag‐name/

Blog URL scheme
/
/message‐uri/
/tag/tag‐name/
/post/

Blog URL scheme
/
/message‐uri/
/tag/tag‐name/
/post/
/message‐uri/post/

Blog URL scheme
/
/message‐uri/
/tag/tag‐name/
/post/
/message‐uri/post/
/message‐uri/comments/

How to parse?

How to parse?
RewriteRules in .htaccess

How to parse?
RewriteRules in .htaccess
^$ /index.pl?page=home

How to parse?
RewriteRules in .htaccess
^$ /index.pl?page=home
^post/?$ /post.pl

How to parse?
RewriteRules in .htaccess
^$ /index.pl?page=home
^post/?$ /post.pl
^([^/]+)/? /index.pl?page=$1

How to parse?
RewriteRules in .htaccess
^$ /index.pl?page=home
^post/?$ /post.pl
^([^/]+)/? /index.pl?page=$1
etc.

How to parse?
RewriteRules in .htaccess
Bad: involves programming
outside Perl

How to parse?
Regular expressions

How to parse?
Regular expressions
given ($uri) {
when (/^\\/$/) {...}
}

How to parse?
Regular expressions
given ($uri) {
when (/^\\/$/) {...}
when (/^\\/post\\/?/) {...}
}

How to parse?
Regular expressions
given ($uri) {
when (/^\\/$/) {...}
when (/^\\/post\\/?/) {...}
# (regexes as in .htaccess)
}

How to parse?
Regular expressions
Bad: rules are not obvious

How to parse?
split builtin

How to parse?
split builtin
@parts = split m{/}, $uri;
given (scalar @parts) {
when (1) {...}
when (2) {...}
}

How to parse?
split builtin
Bad: boring

How to parse?
Grammars

How to parse?
Grammars
Cool!

How to parse?
Grammars
Cool!
Easy to maintain

How to parse?
Grammars
Cool!
Easy to maintain
But might be slow

How to parse?
Grammars
Cool!
Easy to maintain
But might be slow . . .
up to 100 times over regexes.

Gramars
Parse::RecDescent
today
Perl 6 grammars
tomorrow

Gramars
Parse::RecDescent
today
Perl 6 grammars
after Christmas

uri : post EOL
| view EOL

uri : post EOL
| view EOL
post : post‐message
| post‐comment

uri : post EOL
| view EOL
post : post‐message
| post‐comment
view : view‐message
| view‐tag

uri : post EOL
| view EOL
post : post‐message
| post‐comment
view : view‐message
| view‐tag
view‐message : ‘/’ word ‘/’

uri : post EOL
| view EOL
post : post‐message
| post‐comment
view : view‐message
| view‐tag
view‐message : ‘/’ word ‘/’
view‐tag : ‘/tag/’ word ‘/’

uri : post EOL
| view EOL
post : post‐message
| post‐comment
view : view‐message
| view‐tag
view‐message : ‘/’ word ‘/’
view‐tag : ‘/tag/’ word ‘/’
word : /\\w+/

uri : post EOL
| view EOL
post : post‐message
| post‐comment
view : view‐message
| view‐tag
view‐message : ‘/’ word ‘/’
view‐tag : ‘/tag/’ word ‘/’
word : /\\w+/
post‐message : ‘/post/’

uri : post EOL
| view EOL
post : post‐message
| post‐comment
view : view‐message
| view‐tag
view‐message : ‘/’ word ‘/’
view‐tag : ‘/tag/’ word ‘/’
word : /\\w+/
post‐message : ‘/post/’
post‐comment : view‐message ‘/post/’

Actions in grammars

uri : post EOL
| view EOL

uri : post EOL {
$action = ‘post’;
}
| view EOL

uri : post EOL {
$action = ‘post’;
}
| view EOL {
$action = ‘view’;
}

view‐message : ‘/’ word ‘/’
view‐tag : ‘/tag/’ word ‘/’

view‐message : ‘/’ word ‘/’ {
$msg_sid = $item{word};
}
view‐tag : ‘/tag/’ word ‘/’

view‐message : ‘/’ word ‘/’ {
$msg_sid = $item{word};
}
view‐tag : ‘/tag/’ word ‘/’ {
$action = ‘view‐tag’;
$tag = $item{word};
}

http://example.com/twincity/
$action = ‘view’;
$msg_sid = ‘twincity’;

http://example.com/twincity/
$action = ‘view’;
$msg_sid = ‘twincity’;
http://example.com/tag/workshop/
$action = ‘view‐tag’;
$tag = ‘workshop’;

my %uri = (
'/' => {
'type' => 'index',
},
'/alpha/' => {
'type' => 'section',
'sectionUri' => 'alpha',
'sectionPage' => 1,
},
'/beta‐2/34/14/' => {
'type' => 'message',
'sectionUri' => 'beta',
'sectionPage' => 2,
'threadID' => 34,
'threadPage' => 1,
'messageID' => 14,
},
'/‐/' => {
'type' => '404',
});

for $uri (keys %uri) {
$parser‐>parse($uri);
cmp_deeply(
$parser‐>{data},
$uri{$uri},
$uri
);
}

Grammars are
logical

Grammars are
logical,
easy to extend

Grammars are
logical,
easy to extend,
cacheable

Grammars are
logical,
easy to extend,
cacheable,
easy to test

2.
.ini configuration files

Application =
code + configuration

Example: blog
number of messages per page

#!/usr/bin/perl
my $MSG_PER_PAGE = 10;

#!/usr/bin/perl
my $MSG_PER_PAGE = 10;

Load configuration
from external file

Load configuration
from external non-Perl file

<config>
<page_length>10</page_length>
</config>

Question:
XML
or
JSON
or
YAML
?

Answer:
Windows INI

[page]
length=10

[section]
page_length=10
[thread]
page_length=10
[obsene]
replacement=***
[preview]
last_posts=31
last_message_length=200

global.ini local.ini

global.ini local.ini
[page]
length=10
[db] [db]
host=db.int host=localhost
port=3333 port=3306

use Config::INI::Access;
config‐>load(\"conf/config.ini\");

use Config::INI::Access;
config‐>load(\"conf/config.ini\");
config‐>load(\"conf/local.ini\");

use Config::INI::Access;
config‐>load(\"conf/config.ini\");
config‐>load(\"conf/local.ini\");
say config‐>db‐>host;

[db]
host=localhost
port=3306
say config‐>db‐>host;

3.
WWW::Page

WWW::Page
is a kinda MVC

http://example.com/some/page

http://example.com/some/page
/www/example.com/some/page/index.xml

http://example.com/some/page
/www/example.com/some/page/index.xml
XML

http://example.com/some/page
/www/example.com/some/page/index.xml
XML
Perl
XML

http://example.com/some/page
/www/example.com/some/page/index.xml
XML
Perl
XML
XSLT
HTML

http://example.com/some/page
/www/example.com/some/page/index.xml
XML
Perl
XML
XSLT
HTML
Browser

<?xml version=\"1.0\" encoding=\"UTF‐8\"?>
<page
import=\"Import::Client\"
transform=\"view.xsl\"
xmlns:page=\"urn:www‐page\">
<manifest>
<title>WWW::Page Web‐Site</title>
<locale>en‐gb</locale>
<page:keyword‐list/>
</manifest>
<content>
<page:month‐calendar/>
</content>
</page>

use WWW::Page;
use encoding 'utf‐8';
my $page = new WWW::Page ({
'xslt‐root' => \"../data/xsl\",
});
print $page‐>as_string();

<?xml version=\"1.0\" encoding=\"UTF‐8\"?>
<page
import=\"Import::Client\"
transform=\"view.xsl\"
xmlns:page=\"urn:www‐page\">
<manifest>
<title>WWW::Page Web‐Site</title>
<locale>en‐gb</locale>
<page:keyword‐list/>
</manifest>
<content>
<page:month‐calendar/>
</content>
</page>

<?xml version=\"1.0\" encoding=\"UTF‐8\"?>
<page
import=\"Import::Client\"
transform=\"view.xsl\"
xmlns:page=\"urn:www‐page\">
<manifest>
<title>WWW::Page Web‐Site</title>
<locale>en‐gb</locale>
<page:keyword‐list/>
</manifest>
<content>
<page:month‐calendar/>
</content>
</page>

<?xml version=\"1.0\" encoding=\"UTF‐8\"?>
<page
sub Import::Client::keywordList
transform=\"view.xsl\"
xmlns:page=\"urn:www‐page\">
<manifest>
<title>WWW::Page Web‐Site</title>
<locale>en‐gb</locale>
<page:keyword‐list/>
</manifest>
<content>
<page:month‐calendar/>
</content>
</page>

package Import::Client;
sub keywordList
{
my ($this, $page, $node, $args) = @_;
my $sth = $dbh‐>prepare(
\"select keyword, uri from keywords\");
$sth‐>execute();
while (my ($keyword, $uri) = $sth‐>fetchrow_array())
{
my $item =
$page‐>{'xml'}‐>createElement ('item');
$item‐>appendText($keyword);
$item‐>setAttribute('uri', $uri);
$node‐>appendChild($item);
}
return $node;
}

package Import::Client;
sub keywordList
{
my ($this, $page, $node, $args) = @_;
my $sth = $dbh‐>prepare(
\"select keyword, uri from keywords\");
$sth‐>execute();
while (my ($keyword, $uri) = $sth‐>fetchrow_array())
{
my $item =
$page‐>{'xml'}‐>createElement ('item');
$item‐>appendText($keyword);
$item‐>setAttribute('uri', $uri);
$node‐>appendChild($item);
}
return $node;
}

package Import::Client;
sub keywordList
{
my ($this, $page, $node, $args) = @_;
my $sth = $dbh‐>prepare(
\"select keyword, uri from keywords\");
$sth‐>execute();
while (my ($keyword, $uri) = $sth‐>fetchrow_array())
{
my $item =
$page‐>{'xml'}‐>createElement ('item');
$item‐>appendText($keyword);
$item‐>setAttribute('uri', $uri);
$node‐>appendChild($item);
}
return $node;
}

package Import::Client;
sub keywordList
{
my ($this, $page, $node, $args) = @_;
my $sth = $dbh‐>prepare(
\"select keyword, uri from keywords\");
$sth‐>execute();
while (my ($keyword, $uri) = $sth‐>fetchrow_array())
{
my $item =
$page‐>{'xml'}‐>createElement ('item');
$item‐>appendText($keyword);
$item‐>setAttribute('uri', $uri);
$node‐>appendChild($item);
}
return $node;
}

<?xml version=\"1.0\" encoding=\"UTF‐8\"?>
<page
import=\"Import::Client\"
transform=\"view.xsl\"
xmlns:page=\"urn:www‐page\">
<manifest>
<title>WWW::Page Web‐Site</title>
<locale>en‐gb</locale>
<page:keyword‐list/>
</manifest>
<content>
<page:month‐calendar/>
</content>
</page>

<?xml version=\"1.0\" encoding=\"UTF‐8\"?>
<page
import=\"Import::Client\"
transform=\"view.xsl\"
xmlns:page=\"urn:www‐page\">
<manifest>
<title>WWW::Page Web‐Site</title>
<locale>en‐gb</locale>
<page:keyword‐list/>
</manifest>
<content>
<page:month‐calendar/>
</content>
</page>

<keyword‐list>
<item uri=\"http://perl.org/\">Perl</item>
<item uri=\"http://dev.perl.org/\">Perl 6</item>
<item uri=\"http://bbc.co.uk/\">Perl on rails</item>
</keyword‐list>

<?xml version=\"1.0\" encoding=\"UTF‐8\"?>
<page
import=\"Import::Client\"
transform=\"view.xsl\"
xmlns:page=\"urn:www‐page\">
<manifest>
<title>WWW::Page Web‐Site</title>
<locale>en‐gb</locale>
<keyword‐list> . . . </keyword‐list>
</manifest>
<content>
<month‐calendar> . . . </month‐calendar>
</content>
</page>

XML
XSLT
HTML
Browser

Possible improvements

<?xml version=\"1.0\" encoding=\"UTF‐8\"?>
<page
import=\"Import::Client\"
transform=\"view.xsl\"
xmlns:page=\"urn:www‐page\">
<manifest>
<page:keyword‐list remote=\"host2\">
</manifest>
<content>
<page:month‐calendar/>
</content>
</page>

<?xml version=\"1.0\" encoding=\"UTF‐8\"?>
<page
import=\"Import::Client\"
transform=\"view.xsl\"
xmlns:page=\"urn:www‐page\">
<manifest>
<page:keyword‐list remote=\"host2\">
</manifest>
<content>
<page:month‐calendar cache=\"memcached\"/>
</content>
</page>

<?xml version=\"1.0\" encoding=\"UTF‐8\"?>
<page
import=\"Import::Client\"
transform=\"view.xsl\"
xmlns:page=\"urn:www‐page\">
<manifest>
<page:keyword‐list remote=\"host2\">
</manifest>
<content>
<page:month‐calendar cache=\"xml\"/>
</content>
</page>

<?xml version=\"1.0\" encoding=\"UTF‐8\"?>
<page
import=\"Import::Client\"
transform=\"view.xsl\"
xmlns:page=\"urn:www‐page\">
<manifest>
<page:keyword‐list remote=\"host2\">
</manifest>
<content>
<page:month‐calendar transform=\"other.xsl\"/>
</content>
</page>

4.
XSLT

Not .WHAT XSLT is
but .WHY I use it

4a.
XSLT: divide and power

website =
logic + layout

website =
Perl-code + HTML

website =
Perl-code + XML+XSLT

website =
Perl-code + XML+XSLT
Perl programmer XSLT coder

website =
Perl-code + XML+XSLT
Perl programmer XSLT coder

4b.
XSLT: multiple languages

en.xml
<strings>
<months>
<item>January</item>
<item>February</item>
. . .
<item>December</item>
</months>
</strings>

de.xml
<strings>
<months>
<item>Januar</item>
<item>Februar</item>
. . .
<item>Dezember</item>
</months>
</strings>

at.xml
<strings>
<months>
<item>Jänner</item>
<item>Februar</item>
. . .
<item>Dezember</item>
</months>
</strings>

<xsl:variable name=\"str\">
<xsl:copy‐of select=\"
document(
concat($lang, ‘.xml’)
)\"/>
</xsl:variable>

<xsl:variable name=\"str\">
<xsl:copy‐of select=\"
document(
concat($lang, ‘.xml’)
)/strings\"/>
</xsl:variable>

<date day=\"7\" month=\"11\" year=\"2008\"/>

<date day=\"7\" month=\"11\" year=\"2008\"/>
<xsl:value‐of select=\"@day\"/>

<date day=\"7\" month=\"11\" year=\"2008\"/>
<xsl:value‐of select=\"@year\"/>

<date day=\"7\" month=\"11\" year=\"2008\"/>
<xsl:value‐of
select=\"$str/months/item[@month]\"/>

4b.
XSLT: multiple layouts

<?xml version=\"1.0\" encoding=\"UTF‐8\"?>
<page
import=\"Import::Client\"
transform=\"view.xsl\"
xmlns:page=\"urn:www‐page\">
<manifest>
<title>WWW::Page Web‐Site</title>
<locale>en‐gb</locale>
<page:keyword‐list/>
</manifest>
<content>
<page:month‐calendar/>
</content>
</page>

<?xml version=\"1.0\" encoding=\"UTF‐8\"?>
<page
import=\"Import::Client\"
transform=\"pda/view.xsl\"
xmlns:page=\"urn:www‐page\">
<manifest>
<title>WWW::Page Web‐Site</title>
<locale>en‐gb</locale>
<page:keyword‐list/>
</manifest>
<content>
<page:month‐calendar/>
</content>
</page>

<?xml version=\"1.0\" encoding=\"UTF‐8\"?>
<page
import=\"Import::Client\"
transform=\"iphone/view.xsl\"
xmlns:page=\"urn:www‐page\">
<manifest>
<title>WWW::Page Web‐Site</title>
<locale>en‐gb</locale>
<page:keyword‐list/>
</manifest>
<content>
<page:month‐calendar/>
</content>
</page>

<?xml version=\"1.0\" encoding=\"UTF‐8\"?>
<page
import=\"Import::Client\"
transform=\"rss/view.xsl\"
xmlns:page=\"urn:www‐page\">
<manifest>
<title>WWW::Page Web‐Site</title>
<locale>en‐gb</locale>
<page:keyword‐list/>
</manifest>
<content>
<page:month‐calendar/>
</content>
</page>

website =
Perl-code + XML+XSLT
Perl programmer XSLT coder

website =
Perl-code + XML+XSLT
Perl programmer XSLT coder
XSLT coder
XSLT coder
XSLT coder

__END__
Andrew Shitov
http://andy.sh | mail@andy.sh