EDOBE XDOM PMML Manuel d'utilisateur télécharger pdf (Page 51)

Pipeline

A Pipeline object contains a set of bufs and procs. When a pipeline is

executed, it repeatedly executes the procs, which read data from and

to bufs, until no procs can be executed (typically because all of the

data has been processed).

Constructing a

Pipeline

The typical way to construct a pipeline, followed in the example

pipeline-construction functions, is to first create the bufs. Next, the

procs in the pipeline are created. The inputs and outputs of the procs

are specified as bufs, essentially "wiring together" the procs into a

pipeline. Finally, the bufs and procs are encapsulated into a pipeline

object, which can be executed.

Object

Initialization

The basic model for constructing an object is to create it, and then set

various properties to configure it, and then to initialize it. During

initialization, any storage allocation needed before executing the

pipeline is done, according to the set properties.

Proc and Buf objects need to be initialized before they are executed

within a pipeline. Therefore, when they are created, their error string

is set to

"uninitialized". The pipeline execution methods will not

use any procs or bufs with error strings set, so this prevents executing

the pipeline before it is initialized.

Object Name Each object can optionally have a name string. This name is used to

identify the object in status messages.

Error String Each object can have an associated error string. Normally, if no error

has occurred, the error string is the empty string

"". If an error occurs

while initializing or running an object, its error string is set to a string

describing the error. The only way to clear an error is to initialize the

object.

Column Types A buf object, described below, represents a data buffer with rows and

columns, something like an Spotfire S+ data frame. As with a data

frame, different columns can store different types of data. Currently,

there are four different data types: double, factor, string, and

timeDate.

Double

The double type is simple; each value is interpreted as a floating point

number.

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EDOBE XDOM PMML Manuel d'utilisateur Page 51