Scope Example

The following example consists of of 2 programs. The first one is foreign-lexicon2.taq. This has 2 country scopes, one trench and the other german. In each scope a resource is declared with a role to write to disk a names for colors aqua, black, blue and white in the scope language

Here we see a system name "xstream" used for both resources as they share the same provider. Also, a 2-part name is given the template in each role to place it in a specific scope. However, the "colors" template referred to in the role is not defined in the program. This is not an oversight as the compiler automatically creates one in it's absence using the query axiom source as the archetype. In this case, the axiom header names are (aqua, black, blue, white). Here are the axioms that feed the query and the "color_query" query

The second program is foreign-colors2.taq. This features a context list named "colors"

This list is implemented by resource roles. There is one role placed in the french scope and the other in the german scope

The "color" select is declared with a first header name of "colors" to bind it to the context list and this enables translation of color names from foreign languages to English. Here is the solution to the "german.color_query" query for color name "Wasser" which is "aqua" in English

color_query(name=Wasser, red=0, green=255, blue=255)

Resource Cursor

A resource cursor can be declared in a flow body in order to access a resource one record at a time. The postfix '++' increment operator is used to progress through the resource content. dictionary2.taq demonstrates accessing a "lexicon" resource using a resource cursor.

Object Method Examples

The resource provider reads a dictionary file containing words beginning with "i" and selects words starting with characters input as property named "filter". The program selects words starting with "in" followed by "im".

The reason for doing 2 separate searches is to demonstrate resource object methods. These are used to delay opening the dictionary file until the filter property has been set. The program demonstrates that the resource cursor keeps in sync with the resource as it is opened and closed using object methods.

Declaration auto()

The "lexicon" resource declaration has a body so normal automatic resource open can be suppressed.

Scanning Dictionary File

In the following flow sequence, the lexicon search characters are configured, the resource is opened and the cursor loops providing hits until the end of the file is reached, at which point, the resource is closed.

Object Methods

Resource object methods are available to allow program control over opening and closing of a resource, otherwise all resources are opened just before a query is launched and closed when the query is completed. There is also a method for setting properties using expressions as values.

The following methods can be called on a resource object which is identified using the resource name. Note that nune of them return a value:

auto

For auto to suppress normal opening of a resource, if must be called before a query is launched. This is facilitated by adding a body to the resource declaration and placing the auto method call in it. Here is a call to set auto 'false' from a forthcoming example which declares a resource named "lexicon":

It is possible to include other statements in the resource block, but the most likely is a set call to set properties.

set

A property value in a set call can be a literal or a variable. Here is an exampe of a set call to set "timeout" to "5" and "password" to a variable named "secret":

dictionary2.taq

Access Guidelines

A resource cursor supports reverse operation like a normal cursor and using an index for random access, However, in these cases the entire provider content is loaded into memory and this can lead to unresponsiveness when there is a lot of data involved.