Data Transformation is FME's ability to manipulate data.The transformation step occurs during the process of format translation.Data is read,转化，and then written to the new format.
FME Workbench provides many options to control data transformation.Data transformation can be subdivided into two distinct types:Structural Transformationand内容转换.
Structural Transformation
这种类型的转换可能更好地称为reorganization.It refers to FME's ability to channel data from source to destination in an almost infinite number of arrangements.This includes the ability to merge data,divide data,re-order data,and define custom data structures.Transforming a dataset's structure requires knowledge of schemas and how to use FME to manipulate them.
Transforming the structure of a dataset is carried out by manipulating its图式.
内容转换
这种类型的转换可能更好地称为修订.它指的是改变数据集内容的能力。Manipulating a feature's geometry or attribute values is the best example of how FME can transform content.
Content transformation can take place independently or alongside structural transformation.
图式概念
A schema is the structure of a dataset or,more accurately,数据集结构的正式定义。
Each dataset has its own unique structure (schema) that includes feature types (layers),允许的几何尺寸，user-defined attributes,and other rules that define or restrict its content.
When a new workspace is created,FME scans all of the source datasets.由此，它在画布左侧创建数据模式的可视化表示。On the right side,it creates a visual representation of how this schema will be duplicated in the chosen output format.
Here are source and destination schemas as they are represented in Workbench.
画布上的每个对象都是数据集中单独的功能类型。
The workspace reads from left to right.
At this point,读卡器架构表示我们拥有什么(so,FME's view of the source datasets).编写器架构表示what we want(so,the data required by the user).
默认情况下，the Writer schema is a mirror image of the source;differences only occur when demanded by limitations of the selected destination format.This allows Quick Translation to occur with no further editing of the translation by the user.
Viewing the Schema in FME Workbench
模式超出了工作区画布上可以看到的范围；各种对话框中还有其他组件也表示数据集的结构。
Some parts of the schema relate specifically to a single feature type only.Attributes are one such component.这些组件显示在特征类型的“属性”对话框中。
通过单击要素类型右侧的“属性”按钮，可以打开“属性”对话框。
TheFeature Type Properties对话框包含三个或四个选项卡（取决于格式）：
- General: Feature Type name,几何类型，and the name of the parent dataset
- User Attributes: a list of attributes.Each attribute is defined by its name,数据类型，width,and number of decimal places
- Format Attributes
- Format Parameters
Feature Type Names use format-specific terminology,so instead ofFeature Type,“名称参数”标签可能是Feature Class,Layer,Sheet,Table,or whatever terminology is specific to the format of data you are writing.
Reader feature type are disabled by default,since source attributes represent the physical schema of the data.If they were changed,the schema would no longer match the Reader dataset.(Note that it is possible to enable reader feature type editing,但建议仅在某些高级方案中使用此功能。）
模式编辑
As noted,最初，工作区中的编写器模式是源的镜像。However,in many cases the user requires the output to have a different data structure.
模式编辑is the process of altering the destination schema to customize the structure of the output data.一个很好的例子是重命名输出中的属性字段。编辑后，the source schema still represents ‘我们拥有什么',but the destination schema now truly does represent 'what we want.'
可编辑组件
There are a number of edits that can be performed,包括，but not limited to,以下。
- 属性重命名：可以重命名目标架构上的属性。
- Attribute type changes: Any attribute on the writer schema can have a change of type;例如，changing a character field to a number field.The Type column for an attribute shows only values that match the permitted types for that data format.For example,an Oracle schema permits attribute types of varchar or clob.MapInfo does not support these data types so they would never appear in a MapInfo schema.
- 功能类型重命名：您可以更改任何功能类型名称。
- Geometry type changes: This field is only available where the format requires a decision on geometry type.
注：For more information about schema mapping,feature mapping,and attribute mapping,see theFME工作台帮助.