7.3. Expansion Expressions

As the Root entity has a number of attributes and the entity is connected with other entities and their attributes, we need a special way to define them as parameters of configuration or be able to launch one entity metadata under a configuration with a different type of root entity.

For this purpose we use expansion expressions:

• "this. ..." - "this" keyword references a specific instance of an entity. It shall be followed by an attribute of an instance. Additionally, set of attributes of corresponding entities can be chained (see examples below).
• "this.attribute" - "this.fastq"
• "this.attribute.attribute. ..." - chaining allows creating more complex pipeline runs. In this case, each "attribute" keyword will be expanded and used as an input for the next "attribute". For example, "this.control_sample.r1_fastq".

"this.attribute" construction is also useful at Root entity configuration launching step when a user selects metadata:

• Example 1. The root entity for the configuration is "Samples", but user selects a "Pair" in the pop-up window. The "Pair" has a link to two samples as attributes. A user here should define the desired attribute (sample) to launch pipeline with the specified root entity. For example, type "this.control_sample" in Define expression field.
• Example 2. The root entity is "Samples", but user selects "Sample Set" and wants to run the analysis for all the samples in the set.  A user here should type the following expression "this.Samples" in Define expression field.