# GO Tutorial: Build Your Own Ontology II

## Exercise II

### Making Relationships

Download the example file - you may need to right-click on it and choose "Save as...". Load the file into DAG-Edit using "Load terms" from the File menu. Choose "OBO Flat File Adapter" from the pull-down menu at the top and type in a profile name next to File Collection. Click "Add" and using the "Browse" button, locate the downloaded flat file "all.ontology". Click "Commit" to load the file.

There are a set of GO terms under the biological process node. To view them, click on the [+] beside the "biological process" term to expand it. Click on a term to highlight it and view its definition. Its place in the DAG structure can also be seen using the DAG Viewer on the right of the DAG-Edit window.

GO uses two relationships
"is-a" means the child is an instance of the parent
"part-of" means the child makes up a part of the parent

Add "is-a" and "part-of" relationships to the terms to create a mini ontology. To change the relationship type, click on the term and select "Change relationship type to" and the appropriate type from the Edit menu. You can give a term multiple parents by shift-dragging one term on top of another term. Remember that any relationships you make must be true for the parent term and its ancestors.

For this exercise, assume that "part-of" means that the child is always part of the parent. Can you see any extra relationships that could be added if "part-of" meant the child is sometimes but not always a part of the parent?

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