GMLFeatureComposer

Categories

Format Specific

Writes out GML features corresponding to feature types from existing GML application schema.

Configuration

Input Ports

Input features containing attributes and geometries appropriate to particular GML feature types.

Output Ports

Serialized GML documents are output via this port.

Features with duplicate gml_id values within a group are output via this port.

Features with gml_parent_id values referring to non-existing gml_id(s) are output via this port.

Features with no corresponding GML feature types.

Parameters

When enabled, a single GML document may be composed from many features. The document structure, the nesting of features in the document, may be controlled via the gml_id and gml_parent_id attributes. Each feature within a group must have a unique gml_id. Features with duplicate ids are send to the DuplicateIds port. Features with gml_parent_id(s) pointing to non-existing parents are sent to the Orphans port.

Group By

If you do not select Group By attributes, then all features fall into the same group.

When you select Group By attributes, this transformer will compose a GML document, based on the selection in the Group By parameter. Each group of features that have the same values for the Group By attributes will be processed independently of other groups.

Complete Groups

Select the point in processing at which groups are processed:

When All Features Received

This is the default behavior. Processing will only occur in this transformer once all input is present.

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.

There are two typical reasons for using 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 When All Features Received 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.

Application Schema

Use this parameter to specify the XML Schema .xsd file, implementing the existing GML application schema. The parameter is required by the transformer to configure itself so that it may serialize to the various GML feature types found in the schema.

Feature Type Attribute

Optionally specifies the attribute whose value holds the GML feature type. The FME feature type will be used if this attribute is absent.

The attribute specified by this clause must exist in the input features and its value must equal to one of the GML feature types determined from the parsed application schemas.

Output Encoding

The encoding for the GML output.

Output XML Namespace Declarations

This parameter specifies a set of XML namespace declarations that may be used to augment and/or overwrite the namespace declarations in the GML output. The legal values for this parameter are whitespace-separated XML namespace declarations as they would appear in an XML element.

Prefer Polygons Over Surfaces

Determines if FME writes the Geometries as a gml:Polygon or a gml:PolygonPatch. The default value is 'no', which prints out gml:Surface geometries. If 'yes', FME creates the geometry as a gml:Polygon in the output.

Generate Geometry gml:id(s)

A gml_id geometry trait, if present, is used to populate the gml:id attribute of a GML geometry element.

For example, a FME Point with the gml_id trait will be written as <gml:Point gml:id="…">

When this parameter is set to Yes, a gml:id will be automatically generated for GML geometries without a corresponding gml_id geometry trait.

The default value is No.

GML srsName

This parameter allows the user to overwrite the CRS value that is written in the GML geometry’s srsName attribute.

GML SRS Axis Order

This parameter is required when the GML srsName parameter is used. It specifies the axis order for a coordinate tuple in a GML <pos> or <posList> element. The valid values for this parameter are “1,2”, “2,1”, “1,2,3” and “2,1,3”. There is no default value.

Pretty Print

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

Indent Size

This parameter specifies the size of a single indentation.

Replace Tabs with Spaces

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

Map Embedded Objects as

This parameter specifies how embedded GML objects (those containing a gml:id), that are not geometries should be mapped.

By default, these embedded objects are mapped into FME attributes.

If the parameter is set to Geometries, the embedded objects are mapped into FME Geometries, and the embedded object properties are loaded into geometric traits. In turn, nested embedded objects are mapped into nested aggregate geometries.

If the parameter is set to Feature Types, the embedded objects will be mapped into separate FME feature types, and these feature types will have an additional gml_parent_id attribute whose value refers back to its parent feature.

Map Predefined Properties

Specifies whether the default and optional GML feature properties, name and description, should be read.

Map all Substitutable Properties

The GML writer will automatically substitute concrete elements that are substitutable for abstract GML properties. Some GML formats declare properties that are not abstract but are nevertheless head of substitution groups.

Selecting this parameter instructs the GML writer to also generate FME attributes for member elements belonging to the substitution group headed by these non-abstract GML properties.

Add XML Namespace Prefix to

When this option is selected, the FME feature type and attribute names will include the XML Namespace prefixes used in the GML application schema. The prefix will be separated from the names via an underscore.

Map Complex Properties as

Specifies whether GML properties that are defined as a complex type with complex content (that is, those that have embedded children elements) should be mapped as nested list attributes within FME features.

If the value is set to XML Fragments, then the complex properties with complex content are mapped as XML fragments.

Some complex properties, such as those that are recursively defined, cannot be mapped as nested lists. These complex properties will always be mapped as XML fragments, regardless of the setting for this parameter.

Limit Number of Lists in Nested Attributes

This optional parameter can control the depth of nested list attributes.

GML

Name the attribute to contain the GML output.

Editing Transformer Parameters

Using a set of menu options, transformer parameters can be assigned by referencing other elements in the workspace. More advanced functions, such as an advanced editor and an arithmetic editor, are also available in some transformers. To access a menu of these options, click beside the applicable parameter. For more information, see Transformer Parameter Menu Options.

Defining Values

There are several ways to define a value for use in a Transformer. The simplest is to simply type in a value or string, which can include functions of various types such as attribute references, math and string functions, and workspace parameters. There are a number of tools and shortcuts that can assist in constructing values, generally available from the drop-down context menu adjacent to the value field.

Using the Text Editor

The Text Editor provides a convenient way to construct text strings (including regular expressions) from various data sources, such as attributes, parameters, and constants, where the result is used directly inside a parameter.

Text Editor

Using the Arithmetic Editor

The Arithmetic Editor provides a convenient way to construct math expressions from various data sources, such as attributes, parameters, and feature functions, where the result is used directly inside a parameter.

Arithmetic Editor

Conditional Values

Set values depending on one or more test conditions that either pass or fail.

Parameter Condition Definition Dialog

Content

Expressions and strings can include a number of functions, characters, parameters, and more.

When setting values - whether entered directly in a parameter or constructed using one of the editors - strings and expressions containing String, Math, Date/Time or FME Feature Functions will have those functions evaluated. Therefore, the names of these functions (in the form @<function_name>) should not be used as literal string values.

String Functions

These functions manipulate and format strings.

Special Characters

 A set of control characters is available in the Text Editor.

Math Functions

Math functions are available in both editors.
Date/Time Functions Date and time functions are available in the Text Editor.

Math Operators

These operators are available in the Arithmetic Editor.

FME Feature Functions

These return primarily feature-specific values.

FME Parameters

FME and workspace-specific parameters may be used.
Creating and Modifying User Parameters Create your own editable parameters.

Dialog Options - Tables

Transformers with table-style parameters have additional tools for populating and manipulating values.

Row Reordering

Enabled once you have clicked on a row item. Choices include:

  • Add a row
  • Remove a row
  • Move current row up one
  • Move current row down one
  • Move current row to top
  • Move current row to bottom

Cut, Copy, and Paste

Enabled once you have clicked on a row item. Choices include:

  • Cut a row - delete and copy to clipboard
  • Copy a row to the clipboard
  • Paste a row from the clipboard

Cut, copy, and paste may be used within a transformer, or between transformers.

Filter

Start typing a string, and the matrix will only display rows matching those characters. Searches all columns. This only affects the display of attributes within the transformer - it does not alter which attributes are output.

Import

Import populates the table with a set of new attributes read from a dataset. Specific application varies between transformers.

Reset/Refresh

Generally resets the table to its initial state, and may provide additional options to remove invalid entries. Behavior varies between transformers.

Note: Not all tools are available in all transformers.

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