Template Guide

Table of Contents

1. Introduction

Interchange is designed to build its pages based on templates from a database. This document describes how to build templates using the Interchange Tag Language (ITL) and explains the different options you can use in a template.

1.1. Overview

The search builder can be used to generate very complex reports on the database or to help in the construction of ITL templates. Select a "Base table" that will be the foundation for the report. Specify the maximum number of rows to be returned at one time, and whether to show only unique entries.

The "Search filter" narrows down the list of rows returned by matching table columns based on various criteria. Up to three separate conditions can be specified. The returned rows must match all criteria.

Finally, select any sorting options desired for displaying the results and narrow down the list of columns returned if desired. Clicking "Run" will run the search immediately and display the results. "Generate definition" will display an ITL tag that can be placed in a template and that will return the results when executed.

To build complex order forms and reports, Interchange has a complete tag language with over 80 different functions called Interchange Tag Language (ITL). It allows access to and control over any of an unlimited number of database tables, multiple shopping carts, user name/address information, discount, tax and shipping information, search of files and databases, and much more.

There is some limited conditional capability with the [if] tag, but when doing complex operations, use of embedded Perl/ASP should be strongly considered. Most of the tests use Perl code, but Interchange uses the Safe.pm module with its default restrictions to help ensure that improper code will not crash the server or modify the wrong data.

Perl can also be embedded within the page and, if given the proper permission by the system administrator, call upon resources from other computers and networks.

2. About Variable Replacement

Variable substitution is a simple and often used feature of Interchange templates. It allows you to set a variable to a particular value in the catalog.cfg directory. Then, by placing that variable name on a page, you invoke that value to be used. Before anything else is done on a template, all variable tokens are replaced by variable values. There are three types of variable tokens:

__VARIABLENAME__ is replaced by the catalog variable called VARIABLENAME.

@@VARIABLENAME@@ is replaced by the global variable called VARIABLENAME.

@_VARIABLENAME_@ is replaced by the catalog variable VARIABLENAME if it exists; otherwise, it is replaced by the global variable VARIABLENAME.

For more information on how to use the Variable configuration file directive to set global variables in interchange.cfg and catalog variables in catalog.cfg, see the Interchange Configuration Guide.

3. Using Interchange Template Tags

This section describes the different template specific tags and functions that are used when building a your templates.

3.1. Understanding Tag Syntax

Interchange uses a style similar to HTML, but with [square brackets] replacing <chevrons>. The parameters that can be passed are similar, where a parameter="parameter value" can be passed.


    [tag parameter]             Tag called with positional parameter
    [tag parameter=value]       Tag called with named parameter
    [tag parameter="the value"] Tag called with space in parameter
    [tag 1 2 3]                 Tag called with multiple positional parameters
    [tag foo=1 bar=2 baz=3]     Tag called with multiple named parameters
    [tag foo=`2 + 2`]           Tag called with calculated parameter
    [tag foo="[value bar]"]     Tag called with tag inside parameter
    [tag foo="[value bar]"]
        Container text.         Container tag.

Most tags can accept some positional parameters. This makes parsing faster and is, in most cases, simpler to write.

The following is an example tag:

    [value name=city]

This tag causes Interchange to look in the user form value array and return the value of the form parameter city, which might have been set with:

    City: <INPUT TYPE=text NAME=city VALUE="[value city]">

Note: Keep in mind that the value was pre-set with the value of city (if any). It uses the positional style, meaning name is the first positional parameter for the [value ...] tag. Positional parameters cannot be derived from other Interchange tags. For example, [value [value formfield]] will not work. But, if the named parameter syntax is used, parameters can contain other tags. For example:

    [value name="[value formfield]"]]

There are exceptions to the above rule when using list tags such as [item-list], [loop], [query] and others. These tags, and their exceptions, are explained in their corresponding sections.

Many Interchange tags are container tags. For example:

    [set Checkout]

Tags and parameter names are not case sensitive, so [VALUE NAME=something] and [value name=something] work the same. The Interchange development convention is to type HTML tags in upper case and Interchange tags in lower case. This makes pages and tags easier to read.

Single quotes work the same as double quotes and can prevent confusion. For example:

    [value name=b_city set='[value city]']

Backticks should be used with extreme caution since they cause the parameter contents to be evaluated as Perl code using the [calc] tag. For example:

    [value name=row_value set=`$row_value += 1`]

is the same as

    [value name=row_value set="[calc]$row_value += 1[/calc]"]

Vertical bars can also be used as quoting characters, but have the unique behavior of stripping leading and trailing whitespace. For example:

    [loop list="
        k1    A1    A2    A3
        k2    B1    B2    B3"]

could be better expressed as:

    [loop list=|
            k1    A1    A2    A3
            k2    B1    B2    B3

How the result of the tag is displayed depends on if it is a container or a standalone tag. A container tag has a closing tag (for example, [tag] stuff [/tag]). A standalone tag has no end tag (for example, [area href=somepage]. Note that [page] and [order] are not container tags. ([/page] and [/order] are simple macros.)

A container tag will have its output re-parsed for more Interchange tags by default. To inhibit this behavior, set the attribute reparse to 0. However, it has been found that the default re-parsing is almost always desirable. On the other hand, the output of a standalone tag will not be re-interpreted for Interchange tag constructs (with some exceptions, like [include file].

Most container tags will not have their contents interpreted (Interchange tags parsed) before being passed the container text. Exceptions include [calc], [currency] and [seti]. All tags accept the interpolate=1 tag modifier, which causes the interpretation to take place.

3.2. data and field

The [data] and [field] tags access elements of Interchange databases. They are the form used outside of the iterating lists, and are used to do lookups when the table, column/field or key/row is conditional based on a previous operation.

The following are equivalent for attribute names:

    table --> base
    col   --> field --> column
    key   --> code  --> row

The [field] tag looks in any tables defined as ProductFiles, in that order, for the data and returns the first non-empty value. In most catalogs, where ProductFiles is not defined, i.e., the demo, [field title 00-0011] is equivalent to [data products title 00-0011]. For example, [field col=foo key=bar] will not display something from the table "category" because "category" is not in the directive ProductFiles or there are multiple ProductFiles and an earlier one has an entry for that key.

[data table column key]

            accesses      Accesses within the last 30 seconds
            arg           The argument passed in a [page ...] or [area ...] tag
            browser       The user browser string
            host          Interchange's idea of the host (modified by DomainTail)
            last_error    The last error from the error logging
            last_url      The current Interchange path_info
            logged_in     Whether the user is logged in via UserDB
            pageCount     Number of unique URLs generated
            prev_url      The previous path_info
            referer       HTTP_REFERER string
            ship_message  The last error messages from shipping
            source        Source of original entry to Interchange
            time          Time (seconds since Jan 1, 1970) of last access
            user          The REMOTE_USER string
            username      User name logged in as (UserDB)

[field name code]

3.3. set, seti, tmp, tmpn scratch and scratchd

Scratch variables are maintained in the user session, which is separate from the form variable values set on HTML forms. Many things can be controlled with scratch variables, particularly search and order processing, the mv_click multiple variable setting facility and key Interchange conditions session URL display.

There are four tags that are used to set the scratch space: [set variable] value [/set], [seti variable] value [/seti], [tmp variable] value [/tmp], [tmpn variable] value [/tmpn] and and two tags for reading scratch space: [scratch variable] and [scratchd variable].

[set variable] value [/set]

          [set checkout]
          name=required Please enter your name.
          address=required No address entered.
          <INPUT TYPE=hidden NAME=mv_order_profile VALUE="checkout">
          [set substring_case]
          <INPUT TYPE=hidden NAME=mv_profile VALUE="substring_case">
            [calc]$Scratch->{foo} = 'bar'; return;[/calc]

[seti variable] value [/seti]

            [set name=variable interpolate=1] [value something] [/set]

[tmp variable] value [/tmp]

[tmpn variable] value [/tmpn]

[scratch variable]

            [perl] $Scratch->{foo} [/perl]

[scratchd variable]

[if scratch name op* compare*] yes [else] no [/else][/if]

3.4. loop

Loop lists can be used to construct arbitrary lists based on the contents of a database field, a search or other value (like a fixed list). Loop accepts a search parameter that will do one-click searches on a database table (or file).

To iterate over all keys in a table, use the idiom ([loop search="ra=yes/ml=9999"] [/loop]. ra=yes sets mv_return_all, which means "match everything". ml=9999 limits matches to that many records. If the text file for searching an Interchange DBM database is not used, set st=db (mv_searchtype).

When using st=db, returned keys may be affected by TableRestrict. Both can be sorted with [sort table:field:mod -start +number] modifiers. See sorting.

The Interchange Tags Reference has more information on the [loop] tag.

[loop item item item] LIST [/loop]

            [loop prefix=size list="Small Medium Large"]
                [loop prefix=color list="Red White Blue"]
            [loop search="se=Americana/sf=category"]
                [loop-code] [loop-field title]

[if-loop-data table field] IF [else] ELSE [/else][/if-loop-data]

Note: This tag does not nest with other if-loop-data tags.

[if-loop-field] IF [else] ELSE [/else][/if-loop-field]

Note: This tag does not nest with other if-loop-field tags.

[loop-alternate N] DIVISIBLE [else] NOT DIVISIBLE [/else][/loop-alternate]

            [loop-alternate 2]EVEN[else]ODD[/else][/loop-alternate]
            [loop-alternate 3]BY 3[else]NOT by 3[/else][/loop-alternate]


[loop-change marker]


[loop-data database fieldname]


[loop-field fieldname]



                return -1 if '[loop-field weight]' eq '';
                return 1 if '[loop-field weight]' < 1;
                return 0;


              [loop-next][calc][loop-field weight] < 1[/calc][/loop-next]

[loop-price n* noformat*]

[loop-calc] PERL [/loop-calc]

Note: All normal embedded Perl operations can be used, but be careful to pre-open any database tables with a [perl tables="tables you need"][/perl] tag prior to the opening of the [loop].

[loop-exec routine]argument[/loop-exec]

[loop-sub routine]PERL[/loop-sub]

3.5. if

[if type field op* compare*]

The Interchange Tags Reference has more information on the [if] tag.

[if !type field op* compare*]

Allows the conditional building of HTML based on the setting of various Interchange session and database values. The general form is:

        [if type term op compare]
                                    If true, this text is printed on the document.
                                    The [then] [/then] is optional in most
                                    cases. If ! is prepended to the type
                                    setting, the sense is reversed and
                                    this text will be output for a false condition.
        [elsif type term op compare]
                                    Optional, tested when if fails.
                                    Optional, printed on the document when all above fail.

The [if] tag can also have some variants:

        [if explicit]
        [condition] CODE [/condition]
                                    Displayed if valid Perl CODE returns a true value.

Some Perl-style regular expressions can be written:

        [if value name =~ /^mike/i]
                                    This is the if with Mike.
        [elsif value name =~ /^sally/i]
                                    This is an elsif with Sally.
        [elsif value name =~ /^barb/i]
        [or value name =~ /^mary/i]
                                    This is an elsif with Barb or Mary.
        [elsif value name =~ /^pat/i]
        [and value othername =~ /^mike/i]
                                    This is an elsif with Pat and Mike.
                                    This is the else, no name I know.

While the named parameter tag syntax works for [if ...], it is more convenient to use the positional syntax in most cases. The only exception is when you are planning to do a test on the results of another tag sequence:

This will not work:

   [if value name =~ /[value b_name]/]
       Shipping name matches billing name.

Do this instead:

   [if type=value term=name op="=~" compare="/[value b_name]/"]
       Shipping name matches billing name.

As an alternative:

   [if type=value term=high_water op="<" compare="[shipping noformat=1]"]
       The shipping cost is too high, charter a truck.

There are many test targets available. The following is a list of some of the available test targets.

config Directive

            [if config CreditCardAuto]
            Auto credit card validation is enabled.

data database::field::key

            [if data products::size::99-102]
            There is size information.
            No size information.
            [if data products::size::99-102 =~ /small/i]
            There is a small size available.
            No small size available.
            [set code]99-102[/set]
            [if type=data term="products::size::[scratch code]"]
            There is size information.
            No size information.


            [if discount 99-102]
            This item is discounted.


            [if explicit]
                $country = $ values =~{country};
                return 1 if $country =~ /u\.?s\.?a?/i;
                return 0;
            You have indicated a US address.
            You have indicated a non-US address.


            [if file /home/user/www/images/[item-code].gif]
            <IMG SRC="[item-code].gif">
            [if type=file term="/home/user/www/images/[item-code].gif"]
            <IMG SRC="[item-code].gif">


          [if items]You have items in your shopping cart.[/if]
          [if items layaway]You have items on layaway.[/if]


          [if ordered 99-102] ... [/if]
            Checks the status of an item on order, true if item
            99-102 is in the main cart.
          [if ordered 99-102 layaway] ... [/if]
            Checks the status of an item on order, true if item
            99-102 is in the layaway cart.
          [if ordered 99-102 main size] ... [/if]
            Checks the status of an item on order in the main cart,
            true if it has a size attribute.
          [if ordered 99-102 main size =~ /large/i] ... [/if]
            Checks the status of an item on order in the main cart,
            true if it has a size attribute containing 'large'.
            syntax for that one would be:
            [if type=ordered term="99-102" compare="size =~ /large/i"]
            To make sure it is the size that is large and not another attribute,
            you could use:
            [if ordered 99-102 main size eq 'large'] ... [/if]
          [if ordered 99-102 main lines] ... [/if]
              Special case -- counts the lines that the item code is
              present on. (Only useful, of course, when mv_separate_items
              or SeparateItems is defined.)


            [if scratch mv_separate_items]
            Ordered items will be placed on a separate line.
            Ordered items will be placed on the same line.





The field term is the specifier for that area. For example, [if session frames] would return true if the frames session parameter was set.

As an example, consider buttonbars for frame-based setups. You might decide to display a different buttonbar with no frame targets for sessions that are not using frames:

   [if session frames]
       [buttonbar 1]
       [buttonbar 2]

Another example might be the when search matches are displayed. If using the string [value mv_match_count] titles found, it will display a plural result even if there is only one match. Use:

   [if value mv_match_count != 1]
       [value mv_match_count] matches found.
       Only one match was found.

The op term is the compare operation to be used. Compare operations are the same as they are in Perl:

   ==  numeric equivalence
   eq  string equivalence
   >   numeric greater-than
   gt  string greater-than
   <   numeric less-than
   lt  string less-than
   !=  numeric non-equivalence
   ne  string equivalence

Any simple Perl test can be used, including some limited regex matching. More complex tests should be done with [if explicit].

[then] text [/then]

[elsif type field op* compare*]

[else] text [/else]

[condition] text [/condition]


4. Programming

Interchange has a powerful paradigm for extending and enhancing its functionality. It uses two mechanisms, user-defined tags and user subroutines on two different security levels, global and catalog. In addition, embedded Perl code can be used to build functionality into pages.

User-defined tags are defined with the UserTag directive in either interchange.cfg or catalog.cfg. The tags in interchange.cfg are global and they are not constrained by the Safe Perl module as to which opcodes and routines they may use. The user-defined tags in catalog.cfg are constrained by Safe. However, if the AllowGlobal global directive is set for the particular catalog in use, its UserTag and Sub definitions will have global capability.

4.1. Overriding Interchange Routines

Many of the internal Interchange routines can be accessed by programmers who can read the source and find entry points. Also, many internal Interchange routines can be overridden:

   GlobalSub <<EOS
   sub just_for_overriding {
       package Vend::Module;
       use MyModule;
       sub to_override {

The effect of the above code is to override the to_override routine in the module Vend::Module. This is preferable to hacking the code for functionality changes that are not expected to change frequently. In most cases, updating the Interchange code will not affect the overridden code.

Note: Internal entry points are not guaranteed to exist in future versions of Interchange.

4.2. Embedding Perl Code

Perl code can be directly embedded in Interchange pages. The code is specified as:

       $name    = $Values->{name};
       $browser = $Session->{browser};
       return "Hi, $name! How do you like your $browser?";

ASP syntax can be used with:

       $name    = $Values->{name};
       $browser = $Session->{browser};
       Hi, <%= $name %>!
           HTML "How do you like your $browser?";

The two examples above are essentially equivalent. See the perl and mvasp tags for usage details.

The [perl] tag enforces Safe.pm checking, so many standard Perl operators are not available. This prevents user access to all files and programs on the system without the Interchange daemon's permissions. See GlobalSub and User-defined Tags for ways to make external files and programs available to Interchange.

       [perl tables="tables-to-open"*
            failure="Return value in case of compile or runtime error"*

Any Interchange tag (except ones using SQL) can be accessed using the $Tag object. If using SQL queries inside a Perl element, AllowGlobal permissions are required and and the global=1 parameter must be set. Installing the module Safe::Hole along with sharing the database table with <tables=tablename> will enable SQL use.

           # If the item might contain a single quote
           $comments = $Values->{comments};

Important Note: Global subroutines are not subject to the stringent security check from the Safe module. This means that the subroutine will be able to modify any variable in Interchange and will be able to write to read and write any file that the Interchange daemon has permission to write. Because of this, the subroutines should be used with caution. They are defined in the main interchange.cfg file and can't be reached by from individual users in a multi-catalog system.

Global subroutines are defined in interchange.cfg with the GlobalSub directive or in user catalogs which have been enabled through AllowGlobal. Catalog subroutines are defined in catalog.cfg, with the Sub directive and are subject to the stringent Safe.pm security restrictions that are controlled by the global directive SafeUntrap.

The code can be as complex as you want them to be, but cannot be used by operators that modify the file system or use unsafe operations like "system," "exec," or backticks. These constraints are enforced with the default permissions of the standard Perl module Safe. Operations may be untrapped on a system-wide basis with the SafeUntrap directive.

The result of this tag will be the result of the last expression evaluated, just as in a subroutine. If there is a syntax error or other problem with the code, there will be no output.

Here is a simple one which does the equivalent of the classic hello.pl program:

   [perl] my $tmp = "Hello, world!"; $tmp; [/perl]

There is no need to set the variable. It is there only to show the capability.

To echo the user's browser, but within some HTML tags:

   my $html = '<H5>';
   $html .= $Session->{browser};
   $html .= '</H5>';

To show the user their name and the current time:


   my $string = "Hi, " . $Values->{name} ". The time is now ";
   $string .= $Tag->time();


4.3. ASP-Like Perl

Interchange supports an ASP-like syntax using the [mvasp] tag.

       This is HTML.<BR>

   <% HTML "This is code<BR>"; %>
       More HTML.<BR>
   <% $Document->write("Code again.<BR>") %>

If no closing [/mvasp] tag is present, the remainder of the page will also be seen as ASP.

ASP is simple. Anything between <% and %> is code, and the string %> can not occur anywhere inside. Anything not between those anchors is plain HTML that is placed unchanged on the page. Interchange variables, [L][/L] and [LC][/LC] areas will still be inserted, but any Interchange tags will not.

There is a shorthand <% = $foo %>, which is equivalent to <% $Document->write($foo); %> or <% HTML $foo; %>

       This is HTML.<BR>
       [value name] will show up as &#91;value name].<BR>

       &#95_VARIABLE__ value is equal to: __VARIABLE__

   <% = "This is code<BR>" %>

The __VARIABLE__ will be replaced by the value of Variable VARIABLE, but [value name] will be shown unchanged.

Important Note: If using the SQL::Statement module, the catalog must be set to AllowGlobal in interchange.cfg. It will not work in "Safe" mode due to the limitations of object creation in Safe. Also, the Safe::Hole module must be installed to have SQL databases work in Safe mode.

4.4. Error Reporting

If your Perl code fails with a compile or runtime error, Interchange writes the error message from the Perl interpreter into the catalog's error log. This is usually 'catalog_root/error.log'. Error messages do not appear on your web page as the return value of the Perl tag or routine.

You will not have direct access to the 'strict' and 'warnings' pragmas where Interchange runs your perl code under Safe (for example, within a [perl] or [mvasp] tag).

5. Interchange Perl Objects

5.1. A note about Safe

You can access all objects associated with the catalog and the user settings with opcode restrictions based on the standard Perl module Safe.pm. There are some unique things to know about programming with Interchange.

Under Safe, certain things cannot be used. For instance, the following can not be used when running Safe:

   $variable = `cat file/contents`;

The backtick operator violates a number of the default Safe opcode restrictions. Also, direct file opens can not be used. For example:

   open(SOMETHING, "something.txt")
       or die;

This will also cause a trap, and the code will fail to compile. However, equivalent Interchange routines can be used:

   # This will work if your administrator doesn't have NoAbsolute set
   $users = $Tag->file('/home/you/list');

   # This will always work, file names are based in the catalog directory
   $users = $Tag->file('userlist');

5.2. Standard objects and variables

The following is a list of Interchange Perl standard objects are:


            <INPUT TYPE=hidden NAME=foo VALUE=bar>
                        return "Value of foo is $CGI->{foo}";

Actually, you should not do that -- if someone sends you a value you should not output it willy-nilly for security reasons. Filter it first with the [filter] tag as accessed by the $Tag object:

                        my $val = $Tag->filter('encode_entities', $CGI->{foo});
                        return "Value of foo is $val";


            <INPUT TYPE=hidden NAME=foo VALUE='bar'>
            <INPUT TYPE=hidden NAME=foo VALUE='baz'>
            <% = "The values of foo are", join (' and ', @{$CGI_array->{'foo'}}) %>


                'main' => [
                                'code' => '00-0011',
                                'mv_ib' => 'products',
                                'quantity' => 1,
                                'size' => undef,
                                'color' => undef
                                'code' => '99-102',
                                'mv_ib' => 'products',
                                'quantity' => 2,
                                'size' => 'L',
                                'color' => 'BLUE'
                'layaway' => [
                                'code' => '00-341',
                                'mv_ib' => 'products',
                                'quantity' => 1,
                                'size' => undef,
                                'color' => undef


    # Allow searching the User database this page only
    $Config->{NoSearch} =~ s/\buserdb\b//;


NOTE: This object is not present and the below will not work with [calc].

            my $db = $Db{products};
                # Key for a normal table with one primary key
                $key = 'foo';
                # Array reference key for a COMPOSITE_KEY table
                $composite_ary_key = ['foo','bar','buz'];
                # Alternate hash reference key for a COMPOSITE_KEY table
                $composite_hash_key = { key1 => 'foo', key2 => 'bar', key3 => 'buz'};
                # Alternate null-separated key for a COMPOSITE_KEY table
                $composite_nullsep_key = join "\0", 'foo','bar','buz';
                ### Any of the composite key types may be substitued
                ### when COMPOSITE_KEY table
            # access an element of the table
            $field = $db->field($key, $column);
            # set an element of the table
            $db->set_field($key, $column_name, $value);
            # atomic increment of an element of the table
            $db->inc_field($key, $column_name, 1);
            # Return a complete hash of the database row (minus the key)
            $hashref = $db->row_hash($key);
            # Return some fields from a row
            my @fields = qw/sku price description/;
            @values = $db->get_slice($key, \@fields);
            # Set some fields in a row (slice)
            my $key = 'os28004';
            my @fields = qw/price description/;
            my @values = (5.95, "Ergo Roller");
            $array_ref = $db->set_slice($key, \@fields, \@values);
            # Alternate way to set slice
            my $key = 'os28004';
            my %fields = ( price => 5.95, description => "Ergo Roller");
            $array_ref = $db->set_slice($key, \%fields);
            # Perform a SQL query, returning an array of arrays
            # (the equivalent of DBI $sth->fetchall_arrayref)
            $ary = $db->query($sql);
            # Same as above, except receive
            # hash reference of pointers to field positions and
            # array reference containing list of fields
            my $sql = 'select * from products';
            ($ary, $index_hash, $name_ary) = $db->query($sql);
            $fields_returned = join ",", @$name_ary;
            $pointer_to_price = $index_hash->{price};
            # Perform a SQL query, returning an array of hashes
            $ary = $db->query({ sql => $sql, hashref => 1 });
            # see if element of the table is numeric
            $is_numeric = $db->numeric($column_name);
            # Quote for SQL query purposes
            $quoted = $db->quote($value, $column_name);
            # Check configuration of the database
            $delimiter = $db->config('DELIMITER');
            # Find the names of the columns (not including the key)
            @columns = $db->columns();
            # Insert the key column name
            unshift @columns, $db->config('KEY');
            # See if a column is in the table
            $is_a_column = defined $db->test_column($column_name);
            # See if a row is in the table
            $is_present = $db->record_exists($key);
            # Create a subroutine to return a single column from the table
            $sub = $db->field_accessor($column);
            for (@keys) {
                push @values, $sub->($key);
            # Create a subroutine to set a single column in the database
            $sub = $db->field_settor($column);
            for (@keys) {
                $sub->($key, $value);
            # Create a subroutine to set a slice of the database
            $sub = $db->row_settor(@columns);
            for (@keys) {
                $sub->($key, @values);
            # Return a complete array of the database (minus the key)
            @values = $db->row($key);
            # Delete a record/row from the table


NOTE: This object is not present and the below will not work with [calc].

          [perl products]
            my $dbh = $Sql{products}
                or return "Database not shared.";
            my $sth = $dbh->prepare('select * from products')
                or return "Couldn't open database.";
            my @record;
            while(@record = $sth->fetchrow()) {
            $sth = $dbh->prepare('select * from othertable')
                or return "Couldn't open database.";
            while(@record = $sth->fetchrow()) {


            array    Returns a reference to an array of arrays (best)
            hash     Returns a reference to an array of hashes (slower)
            list     Returns a reference to an array of tab-delimited lines
            $DbSearch->{table} = $Db{foo};
            $search = {
                    mv_searchspec => 'Mona Lisa',
                    mv_search_field => [ 'title', 'artist', 'price' ],
                    mv_return_fields    => [ 'title' ]
            my $ary = $DbSearch->array($search);
            if(! scalar @$ary) {
                return HTML "No match.\n";
            for(@$ary) {


This is an object which will allow you to write and manipulate the output of your embedded Perl. For instance, you can emulate a non-parsed-header program with:

                for(1 .. 20) {
                        $Document->write("Counting to $_...<br>");
                        $Document->write( " " x 4096);
                $Document->write("Finished counting!");

Note the write of 4096 spaces. Because Interchange's link program is parsed by default and your web server (and the link program) have buffers, you need to fill up the buffer to cause a write. You can do it without the extra padding if you set the link up as a non-parsed-header program -- see your web server documentation on how to do that.

There are several methods associated with $Document:

         HTML $foo;                     # Append $foo to the write buffer array
         $Document->write($foo);        # object call to append $foo to the write
                                        # buffer array
         $Document->insert($foo);       # Insert $foo to front of write buffer array
         $Document->header($foo, $opt); # Append $foo to page header
         $Document->send();             # Send write buffer array to output, done
                                        # automatically upon end of ASP, clears buffer
                                        # and invalidates $Document->header()
         $Document->hot(1);             # Cause writes to send immediately
         $Document->hot(0);             # Stop immediate send
         @ary = $Document->review();    # Place contents of write buffer in @ary
         $Document->replace(@ary)       # Replace contents of write buffer with @ary
         $ary_ref = $Document->ref();   # Return ref to output buffer




$Document->header($foo, $opt)

            $Document->header("Content-type: text/plain");
            $Document->header("Content-type: text/plain", { replace => 1 } );




            @ary = $Document->review();



            # Remove the first item in the write buffer
            my $ary_ref = $Document->ref();
            shift @$ary_ref;


            HTML $foo, $bar;
            $Document->write($foo, $bar);



           <% $Scratch->{foo} = 'bar'; %>
            [set foo]bar[/set]


                my $out = $Session->{browser};
            [data session browser]
                $Session->{source} = 'New_partner';


IMPORTANT NOTE: If the tag will access a database that has not been previously opened, the table name must be passed in the ITL call. For example:

            [perl tables="products pricing"]
            [perl products pricing]
                my $user = $Session->{username};
                return $Tag->data('userdb', 'name', $user );
            [data table=userdb column=name key="[data session username]"]
            # WRONG!!!
            # Right
            $Tag->data('products', 'title', '00-0011');
            my $opt = {
                            table   => 'products',
                            column  => 'title',
                            key     => '00-0011',
            $Tag->data( $opt );
            $Tag->item_list( {
                                'body' => "[item-code] [item-field title]",
            $Tag->item_list( { }, "[item-code] [item-field title]")


            <% $Document->write($Values->{foo}); %>
            [value foo]


                Log("error log entry");
                Log("\\error log entry without timestamp");
                Log('\another error log entry without timestamp');
                Log("error log entry with timestamp");

6. Debugging

No debug output is provided by default. The source files contain commented-out '::logDebug(SOMETHING)' statements which can be edited to activate them. Set the value of DebugFile to a file that will be written to:

   DebugFile /tmp/icdebug

6.1. Export

                 table => VALUE,
            $Tag->export($table, $ATTRHASH);
                base ==> table
                database ==> table

6.2. Time

                 locale => VALUE,
            $Tag->time($locale, $ATTRHASH, $BODY);

6.3. Import

                 table => VALUE,
                 type => VALUE,
            $Tag->import($table, $type, $ATTRHASH, $BODY);
                base ==> table
                database ==> table
            [import table=orders type=LINE continue=NOTES]
            code: [value mv_order_number]
            shipping_mode: [shipping-description]
            status: pending
            [import table=orders type=LINE continue=NOTES]
            shipping_mode: [shipping-description]
            status: pending
            code: [value mv_order_number]

6.4. Log

                 file => VALUE,
            $Tag->log($file, $ATTRHASH, $BODY);
                arg ==> file

6.5. Header

6.6. price, description, accessories

[price code quantity* database* noformat*]

            [price  code=99-102
                    size=L]              is $10.00
            [price  code=99-102
                    size=XL]             is $11.00
            [price  code=99-102
                    size=XL]             is $11.75
            [price  code=99-102
                    quantity=10]         is $10.00
            [price  code=99-102
                    size=S]              is $9.50

[description code table*]

[accessories code attribute*, type*, field*, database*, name*, outboard*]

            name=Label Text, name=Label Text*
            [accessories TK112 color]
            <SELECT NAME="mv_order_color">
            <OPTION VALUE="beige">Almond
            <OPTION VALUE="gold">Harvest Gold
            <OPTION SELECTED>White
            <OPTION VALUE="green">Avocado


These elements read a file from the disk and insert the contents in the location of the tag. [include ...] will allow insertion of Interchange variables and ITL tags.

[file ...]

[include file]

6.8. Banner/Ad rotation

Interchange has a built-in banner rotation system designed to show ads or other messages according to category and an optional weighting.

The [banner ...] ITL tag is used to implement it.

The weighting system pre-builds banners in the directory 'Banners,' under the temporary directory. It will build one copy of the banner for every one weight. If one banner is weighted 7, one 2 and one 1, then a total of 10 pre-built banners will be made. The first will be displayed 70 percent of the time, the second 20 percent and the third 10 percent, in random fashion. If all banners need to be equal, give each a weight of 1.

Each category may have separate weighting. If the above is placed in category tech, then it will behave as above when placed in [banner category=tech] in the page. A separate category, say art, would have its own rotation and weighting.

The [banner ...] tag is based on a database table, named banners by default. It expects a total of five (5) fields in the table:





            non-zero, non-blank: Rotating ads
            blank:               Ad not displayed
            0:                   Ad is entire contents of banner field


Interchange expects the banner field to contains the banner text. It can contain more than one banner, separated by the string '{or}.' To activate the ad, place any string in the field rotate.

The special key "default" is the banner that is displayed if no banners are found. (Doesn't apply to weighted banners.)

Weighted banners are built the first time they are accessed after catalog reconfiguration. They will not be rebuilt until the catalog is reconfigured or the file tmp/Banners/total_weight and tmp/Banners/<category>/total_weight is removed.

If the option once is passed (i.e., [banner once=1 weighted=1], then the banners will not be rebuilt until the total_weight file is removed.

The database specification should make the weight field numeric so that the proper query can be made. Here is the example from Interchange's demo:

   Database   banner   banner.txt   TAB
   Database   banner   NUMERIC      weight


weighted, categorized

            code    category   weight   rotate   banner
            t1      tech       1                 Click here for a 10% banner
            t2      tech       2                 Click here for a 20% banner
            t3      tech       7                 Click here for a 70% banner
            a1      art        1                 Click here for a 10% banner
            a2      art        2                 Click here for a 20% banner
            a3      art        7                 Click here for a 70% banner
            [banner weighted=1 category="tech"]


            [banner weighted=1]
            code    category   weight   rotate   banner
            t1      tech       1                 Tech banner 1
            t2      tech       2                 Tech banner 2
            t3      tech       7                 Tech banner 3
            a1      art        1                 Art banner 1
            a2      art        2                 Art banner 2
            a3      art        7                 Art banner 3

categorized, not rotating

            [banner category="tech"]
            [data table=banner col=banner key=tech
            code    category   weight   rotate   banner
            tech               0        0        Tech banner
            [banner category="[value interest]"]

categorized and rotating

            [banner category="tech"]
            code    category   weight   rotate   banner
            tech               0        1        Tech banner 1{or}Tech banner 2
            art                0        1        Art banner 1{or}Art banner 2
            [banner category="[value interest]"]

multi-level categorized

            [banner category="tech:hw"] or [banner category="tech:sw"]
            code    category   weight   rotate   banner
            tech               0        1        Tech banner 1{or}Tech banner 2
            tech:hw            0        1        Hardware banner 1{or}HW banner 2
            tech:sw            0        1        Software banner 1{or}SW banner 2


            table       banner    selects table used
            a_field     banner    selects field for banner text
            delimiter   {or}      delimiter for rotating ads
            r_field     rotate    rotate field
            separator   :         separator for multi-level categories
            w_field     weight    rotate field

6.9. Tags for Summarizing Shopping Basket/Cart

The following elements are used to access common items which need to be displayed on baskets and checkout pages.

* marks an optional parameter

[item-list cart*]


[nitems cart*]


[salestax cart*]

[shipping-description mode*]

[shipping mode*]

[total-cost cart*]

[currency convert*]

            [currency convert=1] [calc] 500.00 + 1000.00 [/calc] [/currency]


[cart name]

[row nn]


[col width=nn wrap=yes|no gutter=n align=left|right|input spacing=n]

            width=nn        The column width, including the gutter. Must be
                            supplied, there is no default. A shorthand method
                            is to just supply the number as the first parameter,
                            as in [col 20].
            gutter=n        The number of spaces used to separate the column (on
                            the right-hand side) from the next. Default is 2.
            spacing=n       The line spacing used for wrapped text. Default is 1,
                            or single-spaced.
            wrap=(yes|no)   Determines whether text that is greater in length than
                            the column width will be wrapped to the next line. Default
                            is yes.
            align=(L|R|I)   Determines whether text is aligned to the left (the default),
                            the right or in a way that might display an HTML text
                            input field correctly.


6.10. Item Lists

Within any page, the [item-list cart*] element shows a list of all the items ordered by the customer so far. It works by repeating the source between [item-list] and [/item-list] once for each item ordered.

Note: The special tags that reference item within the list are not normal Interchange tags, do not take named attributes and cannot be contained in an HTML tag (other than to substitute for one of its values or provide a conditional container). They are interpreted only inside their corresponding list container. Normal Interchange tags can be interspersed, though they will be interpreted after all of the list-specific tags.

Between the item_list markers the following elements will return information for the current item:

[if-item-data table column]

Note: This tag does not nest with other [if-item-data ...] tags.

[if-item-data table column]


[if-item-field fieldname]

Note: This tag does not nest with other [if-item-field ...] tags.

[if-item-field fieldname]


[item-accessories attribute*, type*, field*, database*, name*]

[item-alternate N] DIVISIBLE [else] NOT DIVISIBLE [/else][/item-alternate]

            [item-alternate 2]EVEN[else]ODD[/else][/item-alternate]
            [item-alternate 3]BY 3[else]NOT by 3[/else][/item-alternate]



[item-data database fieldname]


[item-field fieldname]



                return -1 if '[item-field weight]' eq '';
                return 1 if '[item-field weight]' < 1;
                return 0;

[item-modifier attribute]


              [item-next][calc][item-field weight] < 1[/calc][/item-next]

[item-price n* noformat*]

[item-discount-price n* noformat*]




[item-modifier-name attribute]


7. Interchange Page Display

Interchange has several methods for displaying pages:

            <FORM ACTION="[process]">
            <INPUT TYPE=hidden NAME=mv_todo VALUE=return>
            <SELECT NAME=mv_nextpage>
            <OPTION VALUE=index>Main page
            <OPTION VALUE=browse>Product listing
            <OPTION VALUE="ord/basket">Shopping cart
            <INPUT TYPE=submit VALUE=Go>

7.1. On-the-fly Catalog Pages

If an item is displayed on the search list (or order list) and there is a link to a special page keyed on the item, Interchange will attempt to build the page "on the fly." It will look for the special page flypage.html, which is used as a template for building the page. If [item-field fieldname], [item-price] and similar elements are used on the page, complex and information-packed pages can be built. The [if-item-field fieldname] HTML [/if-item-field] pair can be used to insert HTML only if there is a non-blank value in a particular field.

Important note: Because the tags are substituted globally on the page, [item-*] tags cannot be used on the default on-the-fly page. To use a [search-region] or [item-list] tag, change the default with the prefix parameter. Example:

   [item-list prefix=cart]
   [cart-code] -- title=[cart-data products title]

To have an on-the-fly page mixed in reliably, use the idiom [fly-list prefix=fly code="[data session arg]"] [/flylist] pair.

[fly-list code="product_code" base="table"] ... [/fly-list]

            prefix=label     Allows [label-code], [label-description]
           [fly-list code="[data session arg]"]
            (contents of flypage.html)
            [page 00-0011] One way to display the Mona Lisa </a>
            [page flypage2 00-0011] Another way to display the Mona Lisa </a>

If the directive PageSelectField is set to a valid product database field which contains a valid Interchange page name (relative to the catalog pages directory, without the .html suffix), it will be used to build the on-the-fly page.

Active tags in their order of interpolation:

[if-item-field field]    Tests for a non-empty, non-zero value in field
[if-item-data db field]  Tests for a non-empty, non-zero field in db
[item-code]              Product code of the displayed item
[item-accessories args]  Accessory information (see accessories)
[item-description]       Description field information
[item-price quantity*]   Product price (at quantity)
[item-field field]       Product database field
[item-data db field]     Database db entry for field

7.2. Special Pages

A number of HTML pages are special for Interchange operation. Typically, they are used to transmit error messages, status of search or order operations and other out of boundary conditions.

Note: The distributed demo does not use all of the default values.

The names of these pages can be set with the SpecialPage directive. The standard pages and their default locations:

canceled (special_pages/canceled.html)

catalog (special_pages/catalog.html)

failed (special_pages/failed.html)

flypage (special_pages/flypage.html)

interact (special_pages/interact.html)

missing (special_pages/missing.html)

            [tag op=header]Status: 404 missing[/tag]

noproduct (special_pages/noproduct.html)

order (ord/basket.html)

search (results.html)

            SpecialPage   search   results

violation (special pages/violation.html)

7.3. Checking Page HTML

Interchange allows debugging of page HTML with an external page checking program. Because leaving this enabled on a production system is potentially a very bad performance degradation, the program is set in a the global configuration file with the CheckHTML directive. To check a page for validity, set the global directive CheckHTML to the name of the program (don't do any output redirection). A good choice is the freely available program Weblint. It would be set in interchange.cfg with:

   CheckHTML  /usr/local/bin/weblint -s -

Of course, the server must be restarted for it to be recognized. The full path to the program should be used. If having trouble, check it from the command line (as with all external programs called by Interchange).

Insert [flag type=checkhtml][/tag] at the top or bottom of pages to check and the output of the checker should be appended to the browser output as a comment, visible if the page or frame source are viewed. To do this occasionally, use a Variable setting:

   Variable  CHECK_HTML    [flag type=checkhtml]

and place __CHECK_HTML__ in the pages. Then set the Variable to the empty string to disable it.

8. Forms and Interchange

Interchange uses HTML forms for many of its functions, including ordering, searching, updating account information and maintaining databases. Order operations possibly include ordering an item, selecting item size or other attributes and reading user information for payment and shipment. Search operations may also be triggered by a form.

Interchange supports file upload with the multipart/form-data type. The file is placed in memory and discarded if not accessed with the [value-extended name=filevar file_contents=1] tag or written with [value-extended name=filevar outfile=your_file_name]. See Extended Value Access and File Upload.

Interchange passes variables from page to page automatically. Every user session that is started by Interchange automatically creates a variable set for the user. As long as the user session is maintained, and does not expire, any variables you set on a form will be "remembered" in future sessions.

Don't use the prefix mv_ for your own variables. Interchange treats these specially and they may not behave as you wish. Use the mv_ variables only as they are documented.

Interchange does not unset variables it does not find on the current form. That means you can't expect a checkbox to become unchecked unless you explicitly reset it.

8.1. Special Form Fields

Interchange treats some form fields specially, to link to the search engine and provide more control over user presentation. It has a number of predefined variables, most of whose names are prefixed with mv_ to prevent name clashes with your variables. It also uses a few variables which are post-fixed with integer digits; those are used to provide control in its iterating lists.

Most of these special fields begin with mv_, and include:

(O = order, S = search, C = control, A = all, X in scratch space)

Name scan Type Description
mv_all_chars ac S Turns on punctuation matching
mv_arg[0-9]+   A Parameters for mv_subroutine (mv_arg0,mv_arg1,...)
mv_base_directory bd S Sets base directory for search file names
mv_begin_string bs S Pattern must match beginning of field
mv_case cs S Turns on case sensitivity
mv_cartname   O Sets the shopping cart name
mv_check   A Any form, sets multiple user variables after update
mv_click   A Any form, sets multiple form variables before update
mv_click   XA Default mv_click routine, click is mv_click_arg
mv_click <name>   XA Routine for a click <name>, sends click as arg
mv_click_arg   XA Argument name in scratch space
mv_coordinate co S Enables field/spec matching coordination
mv_column_op op S Operation for coordinated search
mv_credit_card*   O Discussed in order security (some are read-only)
mv_dict_end de S Upper bound for binary search
mv_dict_fold df S Non-case sensitive binary search
mv_dict_limit di S Sets upper bound based on character position
mv_dict_look dl S Search specification for binary search
mv_dict_order do S Sets dictionary order mode
mv_doit   A Sets default action
mv_email   O Reply-to address for orders
mv_exact_match em S Sets word-matching mode
mv_fail_form   A Sets CGI values to use on failed profile check
mv_fail_href   A Sets page to display on on failed profile check
mv_fail_zero   A Forces zeroing of current form values on failed profile check
mv_field_file ff S Sets file to find field names for Glimpse
mv_field_names fn S Sets field names for search, starting at 1
mv_first_match fm S Start displaying search at specified match
mv_form_profile   A Check form with Interchange profile
mv_head_skip hs S Sets skipping of header line(s) in index
mv_index_delim id S Delimiter for search fields (TAB default)
mv_matchlimit ml S Sets match page size
mv_max_matches mm S Sets maximum match return
mv_min_string ms S Sets minimum search spec size
mv_negate ne S Records NOT matching will be found
mv_nextpage np A Sets next page user will go to
mv_numeric nu S Comparison numeric in coordinated search
mv_order_group   O Allows grouping of master item/sub item
mv_order_item   O Causes the order of an item
mv_order_number   O Order number of the last order (read-only)
mv_order_quantity   O Sets the quantity of an ordered item
mv_order_profile   O Selects the order check profile
mv_order_receipt   O Sets the receipt displayed
mv_order_report   O Sets the order report sent
mv_order_subject   O Sets the subject line of order email
mv_orsearch os S Selects AND/OR of search words
mv_profile mp S Selects search profile
mv_record_delim dr S Search index record delimiter
mv_return_all ra S Return all lines found (subject to range search)
mv_return_delim rd S Return record delimiter
mv_return_fields rf S Fields to return on a search
mv_return_file_name rn S Set return of file name for searches
mv_return_spec rs S Return the search string as the only result
mv_save_session   C Set to non-zero to prevent expiration of user session
mv_search_field sf S Sets the fields to be searched
mv_search_file fi S Sets the file(s) to be searched
mv_search_line_return lr S Each line is a return code (loop search)
mv_search_match_count   S Returns the number of matches found (read-only)
mv_search_page sp S Sets the page for search display
mv_searchspec se S Search specification
mv_searchtype st S Sets search type (text, glimpse, db or sql)
mv_separate_items   O Sets separate order lines (one per item ordered)
mv_session_id id A Suggests user session id (overridden by cookie)
mv_shipmode   O Sets shipping mode for custom shipping
mv_sort_field tf S Field(s) to sort on
mv_sort_option to S Options for sort
mv_spelling_errors er S Number of spelling errors for Glimpse
mv_substring_match su S Turns off word-matching mode
mv_success_form   A Sets CGI values to use on successful profile check
mv_success_href   A Sets page to display on on successful profile check
mv_success_zero   A Forces zeroing of current form values on successful profile check
mv_todo   A Common to all forms, sets form action
mv_todo.map   A Contains form imagemap
mv_todo.checkout.x   O Causes checkout action on click of image
mv_todo.return.x   O Causes return action on click of image
mv_todo.submit.x   O Causes submit action on click of image
mv_todo.x   A Set by form imagemap
mv_todo.y   A Set by form imagemap
mv_unique un S Return unique search results only
mv_value va S Sets value on one-click search (va=var=value)

8.2. Form Actions

Interchange form processing is based on an action and a todo. This can be gated with mv_form_profile to determine actions and form values based on a check for required values or other preconditions.

The predefined actions at the first level are:

   process       process a todo
   search        form-based search
   scan          path-based search
   order         order an item

Any action can be defined with ActionMap.

The process action has a second todo level called with mv_todo or mv_doit. The mv_todo takes preference over mv_doit, which can be used to set a default if no mv_todo is set.

The action can be specified with any of:

page name

            <FORM ACTION="/cgi-bin/simple/search" METHOD=POST>
            <INPUT NAME=mv_searchspec>
            <FORM ACTION="[area search]" METHOD=POST>
            <INPUT NAME=mv_searchspec>
            <FORM ACTION="[process]" METHOD=POST>
            <INPUT TYPE=hidden NAME=mv_todo VALUE=search>
            <INPUT NAME=mv_searchspec>


            <FORM ACTION="[area foo]" METHOD=post>
            <INPUT TYPE=hidden NAME=mv_action VALUE=search>
            <INPUT NAME=mv_searchspec>

The second level todo for the process action has these defined by default:

   back         Go to mv_nextpage, don't update variables
   search   Trigger a search
   submit   Submit a form for validation (and possibly a final order)
   go       Go to mv_nextpage (same as return)
   return   Go to mv_nextpage, update variables
   set      Update a database table
   refresh  Go to mv_orderpage|mv_nextpage and check for
            ordered items
   cancel   Erase the user session

If a page name is defined as an action with ActionMap or use of Interchange's predefined action process, it will cause form processing. First level is setting the special page name process, or mv_action set to do a form process, the Interchange form can be used for any number of actions. The actions are mapped by the ActionMap directive in the catalog configuration file, and are selected on the form with either the mv_todo or mv_doit variables.

To set a default action for a process form, set the variable mv_doit as a hidden variable:

   <INPUT TYPE=hidden NAME=mv_doit VALUE=refresh>

When the mv_todo value is not found, the refresh action defined in mv_doit will be used instead.

More on the defined actions:







8.3. Profile checking

Interchange can check forms for compliance with requirements. The mechanism uses a profile, which is set via the mv_form_profile or mv_order_profile variables.

8.3.1. mv_form_profile

The mv_form_profile checks happen before any other action. They are designed to prevent submission of a form if required parameters are not present.

You define the profiles either in scratch space or with files specified in the OrderProfile directive.

Specifications take the form of an order page variable (like name or address), followed by an equals sign and a check type. There are many provided check types, and custom ones can be defined in a user-specified file using the CodeDef configuration directive.

Standard check types:















            foo=regex ^bar
       foo=regex ^bar "You must have bar at the beginning of this"
       foo=regex !^bar "You may not have bar at the beginning!"


       foo=length 4-10


       foo=unique userdb Sorry, that username is already taken


       foo=filter entities Sorry, no HTML allowed
            foo=filter lower Sorry, no uppercase characters

Also, there are pragmas that can be used to change behavior:



        # Checks credit card number and destroys number after encryption
        # The charge operation can never work
        &charge=custom authorizenet
        # Checks credit card number and keeps number after encryption
        # The charge operation can now work
        &credit_card=standard keep
        &charge=custom authorizenet







        # Success :)
        &return 1
        # Failure :\
        &return 0







As an added measure of control, the specification is evaluated for the special Interchange tags to provide conditional setting of order parameters. With the [perl] [/perl] capability, quite complex checks can be done. Also, the name of the page to be displayed on an error can be set in the mv_failpage variable.

Error messages are set by appending the desired error message to the line containing the check:

city=required Please fill in your city.

This sets the value of the error associated with name, and can be displayed with the error tag:

        [error name=city show_error=1]

8.4. Profile examples

The following file specifies a simple check of formatted parameters:

 name=required You must give us your name.
 address=required Oops! No address.
 phone_day=phone_us XXX-XXX-XXXX phone-number for US or Canada
 email=email Email address missing the domain?

The profile above only performs the &success directive if all of the previous checks have passed -- the &fatal=yes will stop processing after the check of the email address if any of the previous checks failed.

If you want to place multiple order profiles in the same file, separate them with __END__, which must be on a line by itself.

8.5. User defined check routines

User-defined check routines can be defined with CodeDef in a file included in the code/ directory, the same as a UserTag.

 CodeDef foo  OrderCheck
 CodeDef foo Routine <<EOR
 sub {
        # $ref is to Vend::Session->{'values'} hash
        # $var is the passed name of the variable
        # $val is current value of checked variable
        my($ref, $var, $val) = @_;

     my($ref, $var, $val) = @_;

        if($val ne 'bar') {
                return (undef, $var, "The value of foo must be bar");
     else {
         return (1, $var, '');

Now you can specify in an order profile:


Very elaborate checks are possible. The return value of the subroutine should be a three-element array, consisting of:

  1. the pass/fail ('1' or 'undef') status of the check;
  2. the name of the variable which was checked;
  3. a standard error message for the failure, in case a custom one has not been specified in the order profile.

The latter two elements are used by the [error] tag for on-screen display of form errors. The checkout page of the Foundation demo includes examples of this.

8.6. One-click Multiple Variables

Interchange can set multiple variables with a single button or form control. First define the variable set (or profile, as in search and order profiles) inside a scratch variable:

 [set Search by Category]

The special variable mv_click sets variables just as if they were put in on the form. It is controlled by a single button, as in:

   <INPUT TYPE=submit NAME=mv_click VALUE="Search by Category">

When the user clicks the submit button, all three variables will take on the values defined in the "Search by Category" scratch variable. Set the scratch variable on the same form as the button is on. This is recommended for clarity. The mv_click variable will not be carried from form to form, it must be set on the form being submitted.

The special variable mv_check sets variables for the form actions <checkout, control, refresh, return, search,> and <submit>. This function operates after the values are set from the form, including the ones set by mv_click, and can be used to condition input to search routines or orders.

The variable sets can contain and be generated by most Interchange tags. The profile is interpolated for Interchange tags before being used. This may not always operate as expected. For instance, if the following was set:

   [set check]
   [cgi name=mv_todo set=bar hide=1]
   [if cgi mv_todo eq 'search']
   do something

The if condition is guaranteed to be false, because the tag interpretation takes place before the evaluation of the variable setting.

Any setting of variables already containing a value will overwrite the variable. To build sets of fields (as in mv_search_field and mv_return_fields), comma separation if that is supported for the field must be used.

It is very convenient to use mv_click as a trigger for embedded Perl:

   <FORM ...
   <INPUT TYPE=hidden NAME=mv_check VALUE="Invalid Input">

   [set Invalid Input]
   my $type        = $CGI->{mv_searchtype};
   my $spell_check = $CGI->{mv_spelling_errors};
   my $out = '';
   if($spell_check and $type eq 'text') {
       $CGI->{mv_todo}     = 'return';
       $CGI->{mv_nextpage} = 'special/cannot_spell_check';

8.7. Checks and Selections

A "memory" for drop-down menus, radio buttons and checkboxes can be provided with the [checked] and [selected] tags.

[checked var_name value]

[selected var_name value]

            <SELECT NAME="color">
            <OPTION [selected name=color value=blue]> Blue
            <OPTION [selected name=color value=green]> Green
            <OPTION [selected name=color value=red]> Red
            <SELECT NAME=color>
            [loop list="Blue Green Red" option=color]
            <OPTION> [loop-code]

See also the ictags documentation on the [loop] tag.

8.8. Integrated Image Maps

Imagemaps can also be defined on forms, with the special form variable mv_todo.map. A series of map actions can be defined. The action specified in the default entry will be applied if none of the other coordinates match. The image is specified with a standard HTML 2.0 form field of type IMAGE. Here is an example:

<INPUT TYPE=hidden NAME="mv_todo.map" VALUE="rect submit 0,0 100,20">
<INPUT TYPE=hidden NAME="mv_todo.map" VALUE="rect cancel 290,2 342,18">
<INPUT TYPE=hidden NAME="mv_todo.map" VALUE="default refresh">
<INPUT TYPE=image  NAME="mv_todo" SRC="url_of_image">

All of the actions will be combined together into one image map with NCSA-style functionality (see the NCSA imagemap documentation for details), except that Interchange form actions are defined instead of URLs.

8.9. Setting Form Security

You can cause a form to be submitted securely (to the base URL in the SecureURL directive, that is) by specifying your form input to be ACTION="[process secure=1]".

To submit a form to the regular non-secure server, just omit the secure modifier.

8.10. Stacking Variables on the Form

Many Interchange variables can be "stacked," meaning they can have multiple values for the same variable name. As an example, to allow the user to order multiple items with one click, set up a form like this:

<input type=checkbox name="mv_order_item" value="M3243"> Item M3243
<input type=checkbox name="mv_order_item" value="M3244"> Item M3244
<input type=checkbox name="mv_order_item" value="M3245"> Item M3245
<input type=hidden name="mv_doit" value="refresh">
<input type=submit name="mv_junk" value="Order Checked Items">

The stackable mv_order_item variable with be decoded with multiple values, causing the order of any items that are checked.

To place a "delete" checkbox on the shopping basket display:

  <input type=checkbox name="[quantity-name]" value="0"> Delete
  Part number: [item-code]
  Quantity: <input type=text name="[quantity-name]" value="[item-quantity]">
  Description: [item-description]
<input type=hidden name="mv_doit" value="refresh">
<input type=submit name="mv_junk" value="Order Checked Items">

In this case, first instance of the variable name set by [quantity-name] will be used as the order quantity, deleting the item from the form.

Of course, not all variables are stackable. Check the documentation for which ones can be stacked or experiment.

8.11. Extended Value Access and File Upload

Interchange has a facility for greater control over the display of form variables; it also can parse multipart/form-data forms for file upload.

File upload is simple. Define a form like:

   <FORM ACTION="[process-target] METHOD=POST ENCTYPE="multipart/form-data">
   <INPUT TYPE=hidden NAME=mv_todo     VALUE=return>
   <INPUT TYPE=hidden NAME=mv_nextpage VALUE=test>
   <INPUT TYPE=file NAME=newfile>
   <INPUT TYPE=submit VALUE="Go!">

The [value-extended ...] tag performs the fetch and storage of the file. If the following is on the test.html page (as specified with mv_nextpage and used with the above form, it will write the file specified:

   Uploaded file name: [value-extended name=newfile]
   Is newfile a file? [value-extended name=newfile yes=Yes no=No test=isfile]

   Write the file. [value-extended name=newfile outfile=junk.upload]
   Write again with
    indication: [value-extended name=newfile

   And the file contents:
   [value-extended name=newfile file_contents=1]

The [value-extended] tag also allows access to the array values of stacked variables. Use the following form:

   <FORM ACTION="[process-target] METHOD=POST ENCTYPE="multipart/form-data">
   <INPUT TYPE=hidden NAME=testvar VALUE="value0">
   <INPUT TYPE=hidden NAME=testvar VALUE="value1">
   <INPUT TYPE=hidden NAME=testvar VALUE="value2">
   <INPUT TYPE=submit VALUE="Go!">

and page:

   testvar element 0: [value-extended name=testvar index=0]
   testvar element 1: [value-extended name=testvar index=1]
   testvar elements:
    joined with a space:   |[value-extended name=testvar]|
    joined with a newline: |[value-extended
    first two only:    |[value-extended
    first and last:    |[value-extended

to observe this in action.

The syntax for [value-extended ...] is:

named: [value-extended

positional: [value-extended name]

Expands into the current value of the customer/form input field named by field. If there are multiple elements of that variable, it will return the value at index; by default all joined together with a space.

If the variable is a file variable coming from a multipart/form-data file upload, then the contents of that upload can be returned to the page or optionally written to the outfile.










8.12. Updating Interchange Database Tables with a Form

Any Interchange database can be updated with a form using the following method. The Interchange user interface uses this facility extensively.

Note: All operations are performed on the database, not the ASCII source file. An [export table_name] operation will have to be performed for the ASCII source file to reflect the results of the update. Records in any database may be inserted or updated with the [query] tag, but form-based updates or inserts may also be performed.

In an update form, special Interchange variables are used to select the database parameters:

mv_data_enable (scratch)

            [set update_database]
            [if type=data term="userdb::trusted::[data session username]"]
                [set mv_data_enable]1[/set]
                [set mv_data_enable]0[/set]
            <INPUT TYPE=hidden NAME=mv_click VALUE=update_database>








The Interchange action set causes the update. Here are a pair of example forms. One is used to set the key to access the record (careful with the name, this one goes into the user session values). The second actually performs the update. It uses the [loop] tag with only one value to place default/existing values in the form based on the input from the first form:

   <FORM METHOD=POST ACTION="[process]">
    <INPUT TYPE=HIDDEN name="mv_doit" value="return">
    <INPUT TYPE=HIDDEN name="mv_nextpage" value="update_proj">
    Sales Order Number <INPUT TYPE=TEXT SIZE=8
                            VALUE="[value update_code]">
    <INPUT TYPE=SUBMIT name="mv_submit"  Value="Select">
   <INPUT TYPE=HIDDEN NAME="mv_data_table"    VALUE="ship_status">
   <INPUT TYPE=HIDDEN NAME="mv_data_key"      VALUE="code">
   <INPUT TYPE=HIDDEN NAME="mv_data_function" VALUE="update">
   <INPUT TYPE=HIDDEN NAME="mv_nextpage"      VALUE="updated">
   <INPUT TYPE=HIDDEN NAME="mv_data_fields"

   [loop arg="[value update_code]"]
   Sales Order <INPUT TYPE=TEXT NAME="code    SIZE=10 VALUE="[loop-code]">
  Customer No. <INPUT TYPE=TEXT NAME="custid" SIZE=30
                   VALUE="[loop-field custid]">
      Comments <INPUT TYPE=TEXT NAME="comments"
                   SIZE=30 VALUE="[loop-field comments]">
        Status <INPUT TYPE=TEXT NAME="status"
                   SIZE=10 VALUE="[loop-field status]">

       <INPUT TYPE=hidden NAME="mv_todo" VALUE="set">
       <INPUT TYPE=submit VALUE="Update table">

The variables in the form do not update the user's session values, so they can correspond to database field names without fear of corrupting the user session.

8.12.1. Can I use Interchange with my existing static catalog pages?

Yes, but you probably won't want to in the long run. Interchange is designed to build pages based on templates from a database. If all you want is a shopping cart, you can mix standard static pages with Interchange, but it is not as convenient and doesn't take advantage of the many dynamic features Interchange offers.

That being said, all you usually have to do to place an order link on a page is:

   <A HREF="/cgi-bin/construct/order?mv_order_item=SKU_OF_ITEM">Order!</A>

Replace /cgi-bin/construct with the path to your Interchange link.

Copyright 2002-2004 Interchange Development Group. Copyright 2001-2002 Red Hat, Inc. Freely redistributable under terms of the GNU General Public License.