Web template system

A Web template system describes the software and methodologies used to produce web pages and for deployment on websites and delivery over the Internet. Such systems process web templates, using a template engine. It is a web publishing tool present in content management systems, software frameworks, HTML editors, and many other contexts.

File:TempEngWeb016.svg

The basic process: content (from a database), and "presentation specifications" (in a web template), are combined (through the template engine) to mass-produce web documents.

Overview

A web template system is composed of:

• A Template engine: the primary processing element of the system;
• Content resource: any of various kinds of input data streams, such as from a relational database, XML files, LDAP directory, and other kinds of local or networked data;
• Template resource: web templates specified according to a Template language;

The template and content resources are processed and combined by the template engine to mass-produce web documents. For purposes of this article, web documents include any of various output formats for transmission over the web via HTTP, or another internet protocol.

Motivations and typical uses

Mass-production

Various agencies and organizations use web template systems for mass-production of content when slower production alternatives prove unfeasible.

For an introductory overview, a news website is used as example. Suppose a "static website", where all web pages are static, and built by a web designer, that need to add and update pages every day.
A typical strategy to automate the web-designer's "repetitive work" is:

1. choose a web template system to maintain the website;
2. group news items with different presentation needs;
3. specify the "presentation standards" through web templates, for each group of news;
4. specify a content resource to generate or update the content of each news item.

Separation of concerns

Main article: Separation of concerns

For the web designer, when each web page comes from a web template, he/she can think about a modular web page structured with components that can be modified independently of each other. These components may include a header, footer, global navigation bar (GNB), local navigation bar, and content well.

For programmers the template language offers a more restricted logic, only for presentation adaptations and decisions and not for doing complex (business model) algorithms.

For other members of the "site team", a template system frees webmasters to focus on technical maintenance, content suppliers to focus on content, and for all of them more reliability.

Moreover, it has the following advantages to its use:

• Ease of design change: presentation variations on templates are "content invariant", web designer can update presentation without another preoccupations.
• Ease of interface localization: menus and other presentation standards are ease to make uniform, for users browsing on the site.
• Possibility to work separately on design and code by different people at one and the same time.

Formal characterization

File:WebTemplate mathRepres.gif

Elements (C,T,P,R) on the dataflow representation.

Kinds of template systems

There are many public software and commercial packages promoted as being web templates and template engines, but there are a high diversity of disperse kinds of solutions. To select and group them in a systematic way, the first step is to characterize them as template systems.

A second step is to group and identify main properties of each characterized system:

• The architecture of these systems, into a client-server reference model, is the main division criteria for group then -- although the use of diverse modern web cache strategies, architectures can be characterized. There are, as illustrated, three groups: Outside server systems, Server-side systems, and Distributed systems.
• Main attributes:
  • Template languages may be:
    • Embedded or Event-driven.
    • Simple, Iterable, Programmable, or Complex.
    • Specification possession: the standards of the language are controlled by a public or not-public. The possession strategy and the ownership indicate the stability and credibility of the specification. Note that in most jurisdictions language specification cannot be copyrighted, so the possession is not absolute.
  • Template engine possession: it is public or not (ownership rights), indicating if source codes of the template engine are open, or not.

Outside server systems

File:StaticTemplates.gif

Outside server template system architecture.

Web templates in this context produce only static web pages, and can be viewed as a ready-made web design, used to mass-produce "cookie-cutter" websites for rapid deployment.

HTML editors are the typical systems using outside server subsystems. They also commonly include themes in place of CSS styles. In general the template language is to be used only with the editor's software.

FrontPage and Dreamweaver are the most popular editors with template sub-system. A Flash web template uses Macromedia Flash to create visually appealing sites.

System label/name	Platform/editor	Notes
Dreamweaver	Macromedia	HTML authoring. Embedded iterable language.
Flash	Macromedia	Flash authoring.
FrontPage	Microsoft	HTML authoring. Embedded iterable language.
Nvu	Linux/Nvu	HTML authoring.

Many server-side template systems have the option to publish the output pages on the server, where the published pages will be static. It is a common feature on content management systems, like Vignette. But this does not have to be considered an out-server generation.

In the majority of the cases, this "publish option" not interferes with the template system, and it can be made by external software, as Wget.

Server-side systems

File:ServerSideTemplates.gif

Server-side template system.

Server-side dynamic pages began generated by templates with pre-existent software adaptated for this task. This early software was the preprocessors and macro languages, adapted for the web use, running on CGI. Next, a simple but relevant technology was the direct execution made on extension modules, started with SSI.

A lot of template systems are typically used as server-side template systems:

System label/name	Platform/framework	Notes
Amrita Template Library	Ruby	Public. Embedded complex language.
CheetahTemplate	Python	Public. Embedded complex language.
Chip	PHP	Public.
ClearSilver	C, Java, Perl, Python, Ruby	Public. Embedded complex language.
Django	Python	Use the "Django template language".
Evoque Templating	Python including Python 3.0	Embedded simple language.
FreeMarker	Java	Public.
Genshi	Python	Public
Grantlee Template system	C++, Qt_(toolkit)	Port of the Django template system to Qt.
Haml	Ruby or Other	Public.
Hamlets	Java	Public.
HTML::Template	Perl	Public.
Kid	Python
Lasso	LassoSoft, LLC	Proprietary. Interpreted Programming Language and Server
Basic Server Side Includes (SSI)	The basic directives fix a "standard".	Embedded simple language, if exclude exec directive.
Basic Edge Side Includes (ESI)	A SSI-like and alternative "basic language".	Embedded simple language.
Smarty	PHP	Public. Embedded complex language.
Template Alloy	Perl	Public. Embedded complex language. Supports various languages including Template::Toolkit, HTML::Template, Text::Tmpl, as well as Velocity Template Language
Template Power	PHP	Public. Web template#Complex templates.
Template Toolkit	Perl	Public. Embedded complex language.
StringTemplate	Python	Public. Embedded iterable language.
Template Attribute Language (TAL)	Zope, Python, Java, Perl, PHP, XSLT	Public; a.k.a. Zope Page Templates (ZPT); see also TAL Expression Syntax (TALES), Macro Expansion TAL (METAL)
Topsite	Python	Public.
PHPlib	PHPlib	Public. Embedded iterable language.
WebMacro	Java	Public. Embedded iterable language.
WebObjects	Java	Use the WebObjects Builder as engine.
Velocity (Jakarta/Apache)	Java	Public. Use VTL - Velocity Template Language.
Vignette	Proprietary.	Commercial solution. Embedded complex language.
VlibTemplate	PHP	Public.
XSLT (standard language)	Any with an XSLT parser	Standard. Event-driven programmable language.
XQuery (standard language)	Any with an XQuery parser	Standard. Embedded programmable language.
Merge On Browse	AJAX compatible browser	Public. Cross browser, client side templating language which uses AJAX and DHTML to pull together dynamic content and static document structure

Technically, the methodology of embedding programming languages within HTML (or XML, etc.), used in many "server-side included script languages" are also templates. All of them are embedded complex languages.

System label/name	Notes
Active Server Pages (ASP)	Proprietary (Microsoft platform). See also: VBScript, Javascript, PerlScript, etc. extensions for ASP.
eRuby	Public (Ruby).
ColdFusion (CFM)	Proprietary.
JavaServer Pages (JSP)	Public, Java platform.
Active Perl	Public.
PHP	Public.
OpenACS	Public (Tcl).

There are also preprocessors used as server-side template engines. Examples:

Preprocessor	Notes
C preprocessor	Public. Embedded iterable language.
M4	Public. Embedded complex language.

Client-Side Systems

File:ClientSideTemplates.gif

Client-side and distributed (decentralized) template system.

Many web browsers support applying XSLT stylesheets to XML data in the browser itself, providing template functionality in the browser.
Other systems implement template functionality in-browser using JavaScript or other in-browser scripting language :

• jQote - jQuery templating engine
• Jenner
• Pure
• Mjt.Template

Distributed systems

The more simple form are transclusions (HTML frames). In other cases it need Dynamic web pages to run.

Examples:

• Ajax (programming)
• Rich Internet application.

 

See also

• Template (disambiguation)
• Template system
• Web template
• Web template engine
• XSLT