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Whitebeam Templates

Contents

This section of the documentation describes Whitebeam templates and their functionality.

Whitebeam templates are universal "building blocks" that support core services or functions that are common to many e-business processes. As such, the use of Whitebeam templates represents a substantial saving in the complexity, time and cost of developing equivalent back-end functionality in a bespoke system.

While basic JavaScript classes are used to provide utility functions such as image manipulation, HTTP requests, email interface - templates tend to encapsulate a higher level abstraction.

Templates operate as separate processes within the server environment and so do not bloat the process sizes of individual Apache HTTPD processes.

Templates Overview

TemplateDescription
SystemProvides control of the system level page generation and basic Presentation Engine facilities.
SiteThe site template provides a store for site-wide, or global site data.
Contacts Creates, maintains and supplies hierarchical 'contact' information. This template is part of the Whitebeam authentication mechanism.
Catalogue Maintains a hierarchical structure of categories to which items can be attached. Items can also be inter-related.
Audit Intended to store bulk audit or logging information. For example tracking changes to other records within an application
Scheduler Schedules timed events without recourse to system utilities such as cron. Provides a decoupling consumer/supplier model for decoupling functional application components.
Collection The collection template provides a mechinism for grouping, or collecting elements together. The collections are represented by arcs, or relations, that link two elements.
SemaphoreProtection against multiple HTTP processes accessing a critical resource.
CounterShared protected numeric data accessible across HTTPD processes. Support atomic read-modify functions
ChatThe chat template provides all the building blocks required to build an interactive chat room within your Whitebeam application.
PostcodeProvides for the translation of national 'post-codes' into longitude/latitude pairs given a suitable source data set. Currently data sets are known to exist for the UK, Irland and the US (zip-codes)/
GeoProvides a lookup service translating an IP address into a country code. Amongst other applications this has been used to target advertising to specific locales and to restrict access to specific countries.
Log fileProviding safe access to the analog web-stats analysis package (experimental)
Core DefinitionsDetailed definitions of template objects (ROM)

Whitebeam templates are in effect server-side components that interact with the database and maintain the integrity of the business and data model. Templates are developed in various languages (mostly C++) and interact with the database via SQL.

Presentation Pages interact with the required Whitebeam templates, through simple but powerful methods or APIs, to deploy complex and secure e-business applications that are aligned to the business processes of each client. These exported interfaces are described by the Whitebeam Object Model.

This section on templates gives an overview of template concepts and links to available templates.

Concepts

Presentation pages can execute template services through a number of methods or application programming interfaces. Each Whitebeam template typically supports the following methods or qualified versions of them:

MethodDescriptionFeatures

create()

Creates a logical record in the database.

Typically, a template automatically assigns a unique identifier to each new record.

modify()

Modifies the logical record in the database.

Only the properties that need to be modified need be specified. Where a record is being modified using a copy of a previously retrieved record, the properties that need not be modified should be removed (e.g. object.property = void 0;) to improve speed of execution.

remove()

Removes a logical record from the database.

Other related records may be automatically removed or modified.

get()

Retrieves an iterator for the set of records matching the specified search criteria.

Additionally, this method allows the index of the first record to be retrieved from the results-set to be specified. It may also allow partial records to be retrieved.

count()

Retrieves a count of the number of records matching the search criteria.

This method takes the same parameters as get().

An identifier (ID) is a system assigned value that is guaranteed to be a unique in the context that it is used in the database. Typically, an ID is a positive number starting from 100. Although numeric identifiers are incremented in steps of 2, there is no guarantee that it will be continuous for records that are created in succession by any one client application. Where a method returns an ID, a value of -1 indicates an error.

A marker (...Mkr) typically refers to a system assigned (alpha or numeric) string that indicates the status (or relationship) of a record or to a qualifier of the type of identifier specified in a search request.

Template methods accept and return values of different type. The first five are standard JavaScript types, the last two are Whitebeam defined classes:

TypeDescription

String

Alphanumeric characters and special characters. It is suggested that % (percent) and _ (underscore) characters are not used as input data to avoid a clash when these characters are used in keyword searches.

Number

Double precision floating point number

Boolean

0 = false, 1 = true

Array

A data structure of multiple, indexed elements.

Object

An arbitarily complex data structure of types

Binary

A class used for holding files for manipulation within the Presentation Environment. Objects of Binary type support properties of binary data, path to binary data and MIME (Multipurpose Internet Mail Extension) encoding.

Iterator

These are used to return collections of objects when the size of the collection returned is indeterminate but could be very large e.g. the results of an item search from the Catalogue template. An iterator object is like any JavaScript object except it has one very important method defined - getNextRow(). Making this call changes the object's contents to represent the next sequential object in the collection. It also support a setNextRow() method.

Meta-data allows record structures of Whitebeam templates to be extended. An application developer can define a user specific and complex data structures or objects that can be assigned to a meta-data object in an object record and applied to the database. The user-defined object is automatically reconstructed when the record is retrieved.

Whitebeam templates support sophisticated search mechanisms typically through their get() methods. This allows records matching a range of search criteria to be retrieved from the database. It is commonly possible to specify an identifier on which to base the search and to nominate fields in the record structure in which to match up to 4 keywords. The initial implementation is non-case sensitive search.

Special characters % (percent) and _ (underscore) can be used as wildcard characters in a keyword or string search request and can be placed anywhere in a search string. The % character should be placed where any number of characters in that portion of the target string is omitted (e.g. %hite% will find any string containing the consecutive letters ‘hite’ such as ‘This is Whitebeam’). The _ character should be placed where a single character in that position in the target string is omitted (e.g. ‘_hitebeam’ will find any 9 letters ending with ‘hitebeam’ such as ‘Whitebeam’).

The search method returns an iterator object that has the following methods:

getNextRow()     populates the iterator with the next record in the set of search results matching the specified search criteria.

setNextRow()     sets the index of the next record to be retrieved by getNextRow().

The example JavaScript code below shows an iterator loop that retrieves all the records in the result set.

iterator_object = rb.template_object.get( search_object );
while ( iterator_object.getNextRow() )
  write(“Found attribute “+iterator_object.recordID+”<br\>);
Note that the result set may change if other Template methods (e.g. modify() and remove()) are executed whilst iterating through the result set. For example, removing records after being retrieved may cause other records to be skipped.
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