for the ArsDigita Community System
To ensure consistency (and its collateral benefit, maintainability), we define and adhere to standards in the following areas:

File Naming

Under the page root (and the template root if using the Style package): In the Tcl library directory:


File names also appear within pages, as linked URLs and form targets. When they do, always use abstract URLs (e.g., user-delete instead of user-delete.tcl), because they enhance maintainability.

Similarly, when linking to the index page of a directory, do not explicitly name the index file (index.tcl, index.adp, index.html, etc.). Instead, use just the directory name, for both relative links (subdir/) and absolute links (/top-level-dir/). If linking to the directory in which the page is located, use the empty string (""), which browsers will resolve correctly.

File Headers and Page Input

Include the appropriate standard header in all scripts. The first line should be a comment specifying the file path relative to the ACS root directory. e.g.
# /www/index.tcl
# /tcl/module-defs.tcl

For static content files (html or adp), include a CVS identification tag as a comment at the top of the file, e.g.

<!-- standards.adp,v 2000/07/29 20:36:34 ron Exp -->

Using ad_page_contract

For non-library Tcl files (those not in the private Tcl directory), use ad_page_contract after the file path comment (this supersedes set_the_usual_form_variables and ad_return_complaint). Here is an example of using ad_page_contract, which serves both documentation and page input validation purposes:

# www/register/user-login-2.tcl

ad_page_contract {
    Verify the user's password and issue the cookie.
    @param user_id The user's id in users table.
    @param password_from_from The password the user entered.
    @param return_url What url to return to after successful login.
    @param persistent_cookie_p Specifies whether a cookie should be set to keep the user logged in forever.
    @author John Doe (
    @cvs-id standards.adp,v 2000/07/29 20:36:34 ron Exp
} {
    {return_url {[ad_pvt_home]}}
    {persistent_cookie_p f}

Salient features of ad_page_contract:


Using ad_library

For shared Tcl library files, use ad_library after the file path comment. Its only argument is a doc_string in the standard (javadoc-style) format, like ad_page_contract. Don't forget to put the @cvs-id in there. Here is an example of using ad_library:

# tcl/wp-defs.tcl

ad_library {
    Provides helper routines for the Wimpy Point module.

    @author John Doe (
    @cvs-id standards.adp,v 2000/07/29 20:36:34 ron Exp


Non-Tcl Files

For SQL and other non-Tcl source files, the following file header structure is recommended:

-- path relative to the ACS root directory
-- brief description of the file's purpose
-- author
-- created
-- $Id$
Of course, replace "--" with the comment delimiter appropriate for the language in which you are programming.


Page Construction

Construct the page as one Tcl variable (name it page_content), and then send it back to the browser with one call to doc_return, which will call db_release_unused_handles prior to executing ns_return, effectively combining the two operations.

For example:

set page_content "[ad_header "Page Title"]

<h2>Page Title</h2>



db_foreach get_row_info {
    select row_information 
    from bar
} {
    append page_content "<li>row_information\n"

append page_content "</ul>


doc_return 200 text/html $page_content

The old convention was to call ReturnHeaders and then ns_write for each distinct chunk of the page. This approach has the disadvantage of tying up a scarce and valuable resource (namely, a database handle) for an unpredictable amount of time while sending packets back to the browser, and so it should be avoided in most cases. (On the other hand, for a page that requires an expensive database query, it's better to call ad_return_top_of_page first, so that the user is not left to stare at an empty page while the query is running.)

Local procedures (i.e., procedures defined and used only within one page) should be prefixed with "module_" and should be used rarely, only when they are exceedingly useful.

All files that prepare HTML to display should end with [ad_footer] or [module_footer]. If your module requires its own footer, this footer should call ad_footer within it. Why? Because when we adapt the ACS to a new site, it is often the case that the client will want a much fancier display than the ACS standard. We like to be able to edit ad_header (which quite possibly can start a <table>) and ad_footer (which may need to end the table started in ad_footer) to customize the look and feel of the entire site.

Tcl Library Files

Further standards for Tcl library files are under discussion; we plan to include naming conventions for procs.

Data Modeling

Under discussion; will include: standard columns, naming conventions for constraints.


Under discussion.