Web template system

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Web template systems
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.
Web template system Web template Template engine

A Web template system describes the software and methodologies used to produce web pages and for deployment on websites and delivery over the Internet.^{[citation needed]} 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.

Overview

A web template system is composed of^{[citation needed]}:

• 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.^{[citation needed]}

For an introductory overview, a news website is used as example. Consider a "static website", where all web pages are static, built by a web designer, and that needs 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, they 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, not for complex (business model) algorithms.^{[citation needed]}

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", meaning a web designer can update the presentation without wider infrastructural preoccupations.^{[citation needed]}
• Ease of interface localization: menus and other presentation standards are easy to make uniform, for users browsing on the site.^{[citation needed]}
• Possibility to work separately on design and code by different people at the same time.^{[citation needed]}

Formal characterization

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 is a great diversity 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.

Many template systems are a component of a platform or framework. They are referred to as the "platform's template system".

Many template systems have options for change (plug) the template language or for change the template engine.

Outside server systems

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" doesn't interferes with the template system, and it can be made by external software, as Wget.

Server-side systems

Server-side template system

Server-side dynamic pages began to be generated by templates with pre-existent software adapted 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.

Many template systems are typically used as server-side template systems:

System label/name	Platform/framework	Notes
Amrita Template Library	Ruby	Public. Embedded complex language.
Teng	C++, Python, PHP	Public. Opensource project, written in C++. High performance. Embedded complex language.
CheetahTemplate	Python	Public. Embedded complex language.
Chip	PHP	Public.
ClearSilver	C, Java, Perl, Python, Ruby	Public. Embedded complex language.
Closure Templates	Java, JavaScript	Public. Embedded complex language
Dermis	Classic ASP/VBScript	Port of the Smarty template system to Classic ASP/VBScript. Public. Embedded complex language.
Django	Python	Use the "Django template language".
Evoque Templating	Python including Python 3.0	Embedded simple language.
FreeMarker	Java	Public.
Facelets	Java EE	Public. Part of JavaServer Faces
FigDice	PHP	Public. XML-based template directives.
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.
jin-template	Java, PHP	Public.
Jinja2	Python	Public. Embedded complex language.
JScore	PHP + JS	Proprietary. Dependency-Driven programmable language. Along with HTML output, generates JS that dynamically manipulates DOM structure on the client side when variables are changed.
HTML::Template	Perl	Public.
Kid	Python
Lasso	LassoSoft, LLC	Proprietary. Interpreted Programming Language and Server
Mustache	ActionScript, C++, Clojure, CoffeeScript, ColdFusion, D, Erlang, Fantom, Go, Java, server-side JavaScript, Lua, .NET, Objective-C, Perl, PHP, Python, Ruby, Scala	Public.
Basic Server Side Includes (SSI)	The basic directives fix a "standard".	Embedded simple language, if exclude exec directive.
Smarty	PHP	Public. Embedded complex language.
ATal	PHP	Public. Embedded complex language. Smarty/TAL hybrid
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. Embedded complex language.
Template Toolkit	Perl	Public. Embedded complex language.
StringTemplate	Java, C#, 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)
Thymeleaf	Java	Public.
Topsite	Python	Public. "As of 2008-02-20, this project is no longer under active development."
PHPlib	PHPlib	Public. Embedded iterable language.
Psttt! template engine	PHP	Public. External selector value css like file.
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 Markup Language (CFM)	Public (Railo, OpenBD). Proprietary (Adobe ColdFusion).
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.

Edge-side systems

Edge-Side template and inclusion systems. “Edge-side” refers to web servers that reside in the space between the client (browser) and the originating server. They are often referred to as “reverse-proxy” servers. These servers are generally tasked with reducing the load and traffic on originating servers by caching content such as images and page fragments, and delivering this to the browser in an efficient manner.

Basic Edge Side Includes (ESI) is an SSI-like language. ESI has been implemented for content delivery networks. The ESI template language may also be implemented in web browsers using JavaScript and Ajax, or via a browser "plug-in".

Client-Side Systems

Client-side and distributed (decentralized) template system.

Many web browsers can apply an XSLT stylesheet to XML data that transforms the data into an XHTML document, thereby providing template functionality in the browser itself.
Other systems implement template functionality in the browser using JavaScript or another client-side scripting language, including:

• Closure Templates
• EJS
• Jenner
• jQote2
• jTemplates
• Mjt.Template
• Mustache
• Pure
• Tempo JSON templates
• webJS
• Yeast templates
• Merge On Browse

Distributed systems

The most simple form is transclusions (HTML frames). In other cases dynamic web pages are needed.

Examples:

• Ajax
• Rich Internet application.

See also

• Dynamic web page
• Smarty
• TBBS
• Template
• Template system
• UIML (User Interface Markup Language)
• Web template
• Web template engine
• XML Sapiens
• XSLT

External links

• JavaScript template libraries comparison from 2009