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Design Patterns 2
Introduction
Design Patterns for FME Workbench Inspired by Emil Vulpin, formerly of Smallworld
Australia
What is a design pattern? In software engineering, a design pattern is a
general repeatable solution to a commonly occurring problem in software design.
It is a description or template for how to solve a problem that can be used in many different situations.
Design Patterns 3
Introduction
The goal of the Design Patterns are to create FME Workbench designs that are: as generic as possible to all FME Features, and reduce duplication of effort.
There are several benefits including: Minimal amount of Workbench transformers Reduced Workbench complexity Improve Workbench maintainability
Design Patterns 4
Pattern Catalog
Central Workflow Approach
External Attribute Schema Map
External Attribute Value Map
External Style Metadata Map
Bookmarks
FME Custom Transformers
FME Custom Formats
Design Patterns 5
Pattern 1Central Workflow Pattern
The goal of the Central Workflow Pattern is to create an FME Workbench that is: as generic as possible to all FME Features and reduce duplication.
There are several benefits including: Minimal amount of Workbench transformers Reduced Workbench complexity Improve Workbench maintainability
The Central Workflow pattern is applicable to most FME Workbench designs and should be considered before creating a new Workbench
Design Patterns 6
Pattern 1Central Workflow Pattern
Multiple source features enter the central workflow from a single point of entry (Sampler or Cloner)
FME Transformers are added to perform logic in a way that minimizes duplicate transformers
A FeatureTypeFilter is used to distribute features to the appropriate Destination Feature Type Definition
FME Workbench
Source Feature 1
Source Feature 2
Source Feature...N
Single Point of Entry Feature Type Filter
Destination Feature 1
Destination Feature 2
Destination Feature .. N
Central Workflow
Design Patterns 9
Pattern 2External Attribute Schema
Map
The goal of the External Attribute Schema Map pattern is to: simplify the mapping of attribute names between source &
destination feature types Used for complex attribute schema mapping definitions An alternative to common FME Transformers such as
AttributeRenamer and AttributeCopier Benefits of this pattern include:
Simplification of the creation & maintenance of the attribute schema mapping definition
Reusability across different FME Workbench sessions Simplifies the internal attribute connections functionality within
FME Workbench for reasonably large FME Workbenches Easily reversible!
Design Patterns 10
Pattern 2External Attribute Schema Map
FME Workbench reads an external attribute schema map definition The definition defines the mapping from source attribute name to destination
attribute name, i.e.:sw_attribute destination_attributemin_road_id IDname Nameroad_type Road_Type
The external attribute schema map definition can be defined in a number of tabular formats, e.g. Excel, CSV, Access, Oracle, MySQL etc.
Source Feature 1
Source Feature 2
Source Feature...N
Schema Mapper Feature Type Filter
Destination Feature 1
Destination Feature 2
Destination Feature .. N
Attribute 1Attribute 2Attribute ... N
Attribute AAttribute BAttribute ... N
External Attribuite SchemaMap Definition
FME Workbench
Design Patterns 13
FME SchemaMapper Transformer
Wizard with 4 primary parts: Schema Mapping database selection Filter definition Index Mapping (Feature Type Mapping) Attribute Mappings & Value Mapping
At least 11 different solution variations See sample workbench and spreadsheet
Design Patterns 14
Pattern 3External Attribute Value Map
The goal of the External Attribute Value Map pattern is to: simplify the mapping of attribute values (enumerated lists or
domains) between source & destination feature types This pattern is best suited for Workbenches that
require complex and/or large attribute value mapping definitions
Benefits of this pattern include: Simplify the creation & maintenance of the attribute value
mapping definition Promote reusability across different FME Workbench sessions Easy to create the reverse mappings!
Design Patterns 15
Pattern 3External Attribute Value Map
The Workbench reads an external attribute value map definition The definition defines the mapping from source attribute value
to destination attribute value for any FME Feature, i.e.sw_carriage_type Carriage_TypeDual Carriage Divided HighwaySingle Carriage Divided RoadSingle Track Undivided Road
The external attribute value schema map definition can be defined in a number of tabular formats, e.g. Excel, CSV, Access, Oracle, MySQL etc.
FME WorkbenchSource Feature 1
Source Feature 2
Source Feature...N
Joiner Feature Type Filter
Destination Feature 1
Destination Feature 2
Destination Feature .. N
Source Value
External Attribuite Value MapDefinition
Destination Value
Design Patterns 16
Pattern 4External Style Metadata Map
The goal of the External Style Metadata Map pattern is to: Provide a implementation for exporting styling information to stylable
formats with Workbench This pattern is applicable to all Workbench designs that
require the export of style information The export of style metadata is dependent on the
destination format’s level of support for style metadata and FME’s level of support for writing to that format, i.e. ESRI SHAPE no style support, MapInfo has limited style support and AutoCAD DWG more comprehensive style support.
The pattern allows for easy external modification of the styling aspects of the translation by non-FME users
The names of the columns should correspond to the FME format attributes for the target format E.g. mapinfo_line_style, autocad_lineweight
Design Patterns 17
Pattern 4External Style Metadata Map
Smallworld CST FME Workbench
Source Feature 1
Source Feature 2
Source Feature...N
Feature TypeFilter
Destination Feature 1
Destination Feature 2
Destination Feature .. N
Attribute 1Attribute 2Attribute ... N
Meta Attribute AMeta Attribute BMeta Attribute ... N
External Style Metadata MapDefinition
FME Plugin
Style MappingWorkflow
TCP/IP
TICS
Pseudo Attribute 1Pseudo Attribute 2Pseudo Attribute ... N
RWO .. N
RWO 1
RWO 2
Design Patterns 18
Pattern 5Bookmarks
Bookmarks allow you to visually group related areas of a workspace
A naming convention should be used to improve navigation and findability
By employing bookmarks, the pattern will: Improve understandability Ease maintenance by improving navigation
Example Workspace
Design Patterns 19
Pattern 6FME Custom Transformers
FME Custom Transformers allow you to create a single transformer to replace a sequence of transformers from an existing workspace
Therefore, the goal of the FME Custom Transformers pattern is to provide a generic set of FME Custom Transformers that simplify the use of FME Workbench for common related designs
By doing so, the pattern will: Simplify and improve reusability of common solutions Encapsulate complexity from less experienced FME users
Design Patterns 20
Pattern 7FME Custom Formats
FME Custom Formats allow you to wrap different source schemas and transform them to a single common schema
Subsequent workspaces can be written to work with the common input schema
Details of the individual sources and thus hidden and encapsulated
By doing so, the pattern will: Allow parallelism during development Ensure local modifications have minimum impact Result in simpler workspaces