A declarative page is a clipboard page created by execution of a declare pages rule (Rule-Declare-Pages rule type). PROJ-359
The name of a declarative page starts with the prefix
Declare_
. Such pages are created and updated only through
operation of activities identified in a Declare Pages rule. The contents
of these pages are visible but read-only to requestors.
Declarative pages can improve performance and reduce memory requirements when all or many requestors in an application need to access static information or slowly changing information.
For example, a declarative page may hold last night's closing U.S.
stock prices in a Value Group
property indexed by ticker
symbol, so that the property reference
Declare_Stock.Price("IBM") is the closing price for IBM shared.
The first time each evening (after the 4:30 P.M. New York market close)
that a requestor attempts to access the page, the system automatically
loads the page with the latest end-of-day prices. The page can remain
unmodified in memory until the next day's closing.
In other situations, data values are not static but may change infrequently; the system automatically checks the declarative page contents (using a when condition rule) before each property access to see whether a fresh recomputation is needed. For example, a page may list the part numbers or SKU numbers of items that are out-of-stock, extracted from an inventory control system. Recomputation is needed only as often as an out-of-stock condition begins or ends, not each time the inventory changes.
Declarative pages are not created at system startup; they are created only when first accessed.
Ordinarily, declarative pages do not persist; they are not saved to the PegaRULES database but are reconstructed when next accessed and the previous version is expired.
On the Clipboard tool display, declarative pages appear as a group
named Declared Pages
. RULE-676
On the Performance tool full details display, you can review (for your own requestor session) elapsed time and CPU time statistics associated with creating, finding, and accessing declarative pages, and counts of the number of node-level declarative pages your requestor has accessed.
The system maintains node-level declarative pages in a cache.
expired page, node, page | |
About
Declare Pages rules Understanding page names and reserved pages Understanding caching About the Performance tool |
|
Atlas — Standard Declare Pages rules |