This attribute accepts "true" or "false".  Relationship fields establish links between records.  If the Dependency attribute is "true" the relationship between records will be one to one.  If "false", the relationship will be one to many.  If the attribute is not included the default for Dependency will be "false" and the relationship will potentially be many to many.

The relationships that are built in to Brick River 'out of the box' features are one to many.  One Blog Post can have many Authors, and one Author can compose many Blog Posts.

<View Id="Recipes" TableId="Content" Name="Recipes"  Plural="Recipes" Singular="Recipe" >
    <Relationship Id="Ingredients" TableId="Content" ViewId="Ingredients" Dependent="true" Cmd="After:Description" />

In the View above, records in the Recipe View may have related records in the Ingredients View.

With the attribute Dependent="true" each Ingredient record is uniquely linked to it's Recipe record.  The ingredient 'Sugar' for the Pie recipe will be different from the ingredient 'Sugar' for the Cake recipe.  This can be useful here because the ingredient record can store an amount field which will be different for pie and cake. 

If the attribute were Dependent="false" the single ingredient record for 'Sugar' would be linked to both Pie and Cake.