XMLAppender

Input features containing the main XML document.

Input features containing the XML fragments.

This is the output for the main XML document with the appended fragments.

Multiple main documents are allowed only if the Group By parameter is used, otherwise duplicate main documents are output via this port. The main documents are considered a duplicate of each other when the values of their composite Group By key equal.

Fragments with no corresponding Group By main XML document are output via this port.

Use this parameter to organize multiple main documents and fragments into groups. Multiple main XML documents are allowed when their composite Group By key differ. Unused documents and fragments, those without corresponding keys, are routed to the UnusedDocument and UnusedFragment ports, respectively.

Process At End (Blocking): This is the default behavior. Processing will only occur in this transformer once all input is present.

Process When Group Changes (Advanced): This transformer will process input groups in order. Changes of the value of the Group By parameter on the input stream will trigger processing on the currently accumulating group. This may improve overall speed (particularly with multiple, equally-sized groups), but could cause undesired behavior if input groups are not truly ordered.

Considerations for Using Group By

There are two typical reasons for using Process When Group Changes (Advanced) . The first is incoming data that is intended to be processed in groups (and is already so ordered). In this case, the structure dictates Group By usage - not performance considerations.

The second possible reason is potential performance gains.

Performance gains are most likely when the data is already sorted (or read using a SQL ORDER BY statement) since less work is required of FME. If the data needs ordering, it can be sorted in the workspace (though the added processing overhead may negate any gains).

Sorting becomes more difficult according to the number of data streams. Multiple streams of data could be almost impossible to sort into the correct order, since all features matching a Group By value need to arrive before any features (of any feature type or dataset) belonging to the next group. In this case, using Group By with Process At End (Blocking) may be the equivalent and simpler approach.

Note: Multiple feature types and features from multiple datasets will not generally naturally occur in the correct order.

As with many scenarios, testing different approaches in your workspace with your data is the only definitive way to identify performance gains.

Selecting from the list enables that selection's corresponding parameter:

• Attribute with XML Document: Choose the attribute containing the main XML document.
• XML Document Filename: Browse to the XML file.

This parameter controls how the fragments are inserted into the document in relation to a selected or matched element. The possible values for the parameter are:

• Preceding Children
• Succeeding Children
• Preceding Siblings
• Succeeding Siblings

The values are to be understood in relation to the selected or matched element, which is specified by the Append Path In Document parameter.

The default value for this parameter is Succeeding Children.

This parameter specifies a single element, or a path to a single element, in the document. Each element in the path is separated by a forward slash, ‘/’. A wildcard, ‘*’, may also be used as the prefix or local-name of the element (for example, ‘*:e’, ‘p:*’, or just ‘*’, which translates to ‘*:*’).

The parameter’s default value is the empty string. This will match or select the root element.

Consider the following XML document:

<data>

<metadata>…</metadata>

<initialize>…</initialize>

<!--Insert XML fragments here -->

<finalize>…</finalize>

</data>

To insert fragments after the <initialize> element we can either:

1) Specify Append Path In Document as "data/initialize", and

2) Set Append Fragments As to Succeeding Siblings

or:

1) Specify Append Path In Document as "data/finalize", and

2) Set Append Fragments As to Preceding Siblings

Selecting from the list enables that selection's corresponding parameter:

• Attribute with XML Fragment: Choose the attribute containing the XML Fragment.
• XML Fragment Filename: Browse to the XML file.

Selecting from the list enables that selection's corresponding parameter:

• Attribute with XML Output: Choose the attribute to hold the appended results.
• XML Output File: Specifies the file to contain the appended results.

This parameter is used to select the encoding for the appended results.

The parameter specifies if the XML output should be pretty-printed with indentation.

This parameter specifies the size of a single indentation.

By default, the tab character is used for pretty printing, use this parameter to replace the tabs with spaces.

By default, the text within a tag is left untouched. If this parameter is set to Yes, the text will be pretty printed. If a tag contains both a text value element and another nested tag element, the second of either the text value or nested tag will not be pretty printed. The example below shows a block of XML code on the left along with its pretty printed output on the right.