Definition of Whitebeam XML Tags

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Definition of Whitebeam XML Tags

rb:cachecontrol

Control client-side caching of this Pattern Page

Body

The body of this tag is always empty.

Attributes

Attribute Required Description

cache

required

yes, private, noheaders or no. If this attribute has the value 'yes' then network devices are allowed to cache this page. If it is set to 'no' then the page may not be cached. If the attribute is set to 'private' then only the client device making the request may cache the results.

If set to noheaders then Whitebeam generates no cache headers and the application can generate the headers it requires. This is the equivalent to calling rb.page.cache() with no parameters.

max-age

implied

Only used if 'cache' is set to either yes or private. In both of these cases setting the 'max-age' attribute will cause the Presentation Engine to generate a 'Max-Age' directive in the Cache-Control HTTP header. If this attribute is not set then the Presentation Engine set's neither the Max-Age directive or an 'Expires' header.

modified

implied

Tells the Presentation Engine which value to include in the HTTP 'Last-Modified' header. The default is that this parameter is set to 'now' (the time at this moment'). You can over-ride this by setting this parameter to 'file' - meaning the time at which the source Pattern Page was last modified.

Remarks

This tag allows a Pattern Page to control the value in the HTTP header that determines whether the page can be cached by the browser and/or any intermediate device. By default the cache control header is set to "no cache" on rhtm pages. However some pages, although generated dynamically, have contents that seldom change (for example the page you are looking at now). This tag allows you to override the default setting as in <rb:cachecontrol cache="yes" />.

There are yet other pages that - although basically static - are different for each user. In this case you want to allow the client device to cache the content while preventing intermediate devices from so doing. You can achieve this by setting the 'cache' attribute to private,

To control caching to a finer level you can specify a 'max-age' for the page in cache using the 'max-age' attribute. This specifies the number of seconds before the page should be expired from conformant caches. If specified this value is used to construct a max-age directive on the Cache-Control header and to create an Expires header.

Finally - you can specify the 'Last-Modified' header date for the page generated. This is used hueristically by advanced web caches to derive how safe a cached page is. By default the Presentation Engine inserts the current data and time. This attribute can be set to either 'now' or 'file'. If 'file' is specified then the date is taken from the last modified date of the source Pattern Page being used to generate the web page.

Note finer granualrity of the modified date can be achieved through the JavaScript rb.page.modified method.
Whitebeam release 1.3.36
(loadtime : 8ms)