FME Questions Importent

 FME Questions Importent

FME Interview Questions

 

1.    What is FME?

 

Answer: FME stands as Feature Manipulation Engine, the data integration platform with the best support for spatial data worldwide. 

FME  was designed to overcome many of the problems associated with traditional translation methods.

 

 

2.    What is ETL?

Answer: ETL (Extract, Transform and Load) can be described as a dataset tool that extracts data from a source, transforms it to fit the users’ needs, and then loads it into a destination or dataset.

FME was the first tool designed to be a spatial ETL application, focusing on translation of geographic data. Today, FME's ETL capabilities cover many different kinds of data, both spatial and non-spatial.

 

 

3.    What is Readers and Writers in FME?

Answer: A Reader is an FME term for the object in a translation that reads a source dataset and a Writer is the FME term for the object in a translation that writes to a destination dataset.

 

4.    What is a Fanout?

Answer: A fanout is a way within FME to split output data based upon the value of an attribute. The data is divided at the time of writing, rather than within the workspace itself.

There are two types of fanout: Feature Type Fanout and Dataset Fanout.

 

1) Feature Type Fanout:

A Feature Type Fanout delivers data to multiple feature types (layers/tables) within a single dataset. 

2) Dataset Fanout: A Dataset Fanout delivers data to the same feature type, but in multiple datasets.

 

 

5.    What are Dynamic Translations?

Answer: Dynamic Translations are a way to create "schema-less" workspaces. The source and destination schema reflect the structure of the source data (what we have) and the structure of the destination data the user requires (what we want).

The layout of a dynamic translation does not reflect either the source or destination schema. It’s a universal layout that is designed to handle data regardless of the schema used by the source data. 

 

6.What is a Group transformer in FME?

Answer: FME transformers carry out transformations on either one feature at a time, or on a whole set of features at once.
For example, the AreaCalculator transformer operates on one feature at a time (to measure the area of a single polygon feature). We call it a feature-based transformer.
The StatisticsCalculator operates on multiple features at a time (to calculate an average value for them all). In FME we call this set of features a group and the transformer is a group-based transformer.

 

7.    What is difference between FeatureJoiner versus FeatureMerger?

 

Answer: 

·   If the join requirements are simple, FeatureJoiner should give better performance.

·   If join requirements are more complex, such as constructing keys, using expressions, naming conflict resolution, consider using the FeatureMerger.

·   If you wish to get only one joined feature, regardless of the number of joins (1:M join produces 1 feature with a list of joins, rather than 1 feature for each join as the FeatureJoiner does), use the FeatureMerger.

·  The FeatureJoiner does not perform some of the advanced list building or geometry handling operations that the FeatureMerger does, but these may be possible by using the FeatureJoiner plus other transformers.

·  The FeatureMerger may be able to join features with different coordinate systems.

 

8. What is used of SpatialFilter Transformer?

Answer: 

-> The SpatialFilter - as its name suggests - filters data according to a spatial relationship. However, it does also merge attributes from one feature to another, therefore can be said to be a type of Spatial Join.

-> Spatial relationships (also known as predicates) define how two or more spatial features interact with each other.

·       For example, two features might intersect each other (or not, in which case they are disjoint), they might touch each other (where the boundaries intersect, but the interiors do not), or one feature might contain a second feature (which itself is therefore within the first feature).

 

 

9. How FME Processes Coordinate Systems in the Workspace?

Answer: 

1) If a coordinate system is specified in both the source format and the workspace, the coordinate system in the workspace is used. The coordinate system specified in the source format is not used, and a warning is logged.

2) If a source coordinate system is not specified in the workspace and the format or system does not store coordinate system information, then the coordinate system is not set for the features that are read. 

3) If a destination coordinate system is set and the feature has been tagged with a coordinate system, then a coordinate system conversion is performed to put the feature into the destination system. This happens right before the feature enters into the destination writer.

4)  If the destination coordinate system was not set, then the features are written out in their original coordinate system.

 

10. Why use Bookmarks?

Answer : Bookmarks play an important role in a well-styled workspace for a number of reasons, including these.

· Design: As a way to subdivide a workspace and manage those sections

· Access: As a marker for quick access to a specific section of a workspace

· Editing: As a means to move groups of transformers at a time

· Performance: As a means to improve workspace performance when caching data.

 

11.What is a Custom Transformer?

Answer: A custom transformer is a sequence of standard transformers condensed into a single transformer. Any existing sequence of transformers can be turned into a custom transformer.

 

Custom Transformer Purposes

Among other functions, custom transformers help to:

1) Reuse Content

o A sequence of transformers encapsulated in a single object can be reused throughout a workspace and shared with colleagues.

2) Employ Advanced Functionality

o  Using a Custom Transformer enables additional functionality to be used, such as looping and parallel processing

3) Tidy Workspaces

o By condensing chunks of content, the workspace canvas becomes less cluttered

 

12.What is a Loop?

Answer: A loop is a programming structure that allows an action to be implemented repeatedly.

Often this is used to carry out iteration; where a process repeats to gradually narrow the process to the desired result. Usually, a loop is linked to a condition; i.e., the action continues until a certain condition is met.

In FME, loops are a way to repeat a section of transformers multiple times, without having to duplicate that section. For technical reasons, loops are only permitted inside a custom transformer.

 

13.What are List Attributes in FME?

Answer: List attributes are FME's way of allowing multiple values per attribute. For example, rather than creating a text field named FRUITS that stores the value “Apple, Orange, Pear”, a user can create a list, which is more structured and can be broken down into constituent parts for processing:

Fruits{0}: Apple 

Fruits{1}: Orange 

Fruits{2}: Pear 

 

 

14.What is Filtering?

Answer: Filtering is the technique of subdividing data as it flows through a workspace. It’s the case where there are multiple output connections from a transformer, each of which carries data to be processed differently. 

A filtering transformer may be any transformer with multiple output ports, such as the GeometryFilter or Sampler transformers, the latter of which creates a sample selection of data and separates it out through Sampled and NotSampled output ports.

 

15.What is the used of  GeometryFilter ?

Answer: 

· Filtering out unwanted geometry types; for example, removing non-linear features before using an AreaBuilder transformer

· Validating geometry against a list of permitted types; for example, where the dataset is constrained to either point or area features (above)

· Dividing up geometry types to write to separate destination Feature Types; for example, when writing to a geometry-restricted format such as Esri Shapefile.