Graphing and Chart Layout - Many Questions - Megapost

There are many concepts related to diagramming and I’m very confused on how they relate and effect one another. FYI, I have the newest version of OmniGraffle (7.4), and bought the pro version.

1. Outline of objects in the left sidebar (composed of topics, and indented objects)

How is a topic different than an object?

2. Sub graphs and groups

Is group as sub-graph the same as grouping objects, but in a way that it has a ‘container’ and is expandable and collapsible?

How do the ‘group’ and ‘group as sub graphs’ interact with each other, i.e. if a sub graph is in a group, or a group in a sub graph

3. Object hierarchy, ranking, and relationships

What is the difference and/or relationship between object rank and hierarchy?

Conflicts: it appears objects can have different ranks in the properties inspector, but they can be set to contradict object hierarchy. For instance, if I have the objects, Fish and Dog all connected via lines (fish drawn first, then dog - so fish is the parent (start?) of all of them, therefore (dog is below fish and indented in the outline pane) but then fish and dog are both set to minimum rank.

Whats the difference between ‘add sibling’ and ‘add spouse’ contextual commands - don’t they both create peers?

I have no idea what an aunt relationship is, and how it is different than a parent.

4. Auto layout

How does object hierarchy and rank effect auto layout

it is my understanding that auto layout defines the default spacing and orientation of objects? Is this accurate? This option doesn’t seem to work, as I can create related objects in any place, angle, and distance with the diagram tool. It seems like the auto layout checkbox doesn’t change behavior of placed objects at all. Why is this so?

It is my understanding that the lay out now button lays out selected (or non-selected too) objects if they are created on a canvas that previously didn’t have auto layout selected. Is this accurate. This option doesn’t seem to work, as when I select objects (all or some) or have none selected, clicking this button does nothing.

When objects in a diagram are selected, the diagram type doesn’t change anything when I change the layout type.
All in all, I think the documentation doesn’t go into enough depth on diagramming, and this is a core feature of this app! How do I learn more?

5.0 Apply Diagram style

When I apply a diagram style to a diagram I created, I cannot undo it if I change my mind with the undo command. Why is this? How can I clear all styles? Or do I have to create a named style (i.e. default) and apply that to all elements?

Hypotheses and findings

(am I correct about these?)

A. Object Rank is all about visual representation and is related to the diagram layout inspector for the canvas. At first, the hierarchy and rank are the same. But when the rank is change, the rank does not alter the hierarchy (parent-child relationships, etc), but can override it for presentation purposes. Thus, returning diagram elements (aka topics, or shapes with connection lines) to default will then return the visual presentation to sync up with / reflect the object hierarchy.

B. Auto layout (and its related button “Layout Now”) sometimes breaks. Fixing this involves copying the diagram, creating a new canvas with auto layout, then pasting it. If that doesn’t work, quitting and re-opeing the app usually works.

C. The ’same rank’ option only works when the objects selected start off at the same rank. Then when one changes, the other previously selected ones do too. (This is counterintuitive, as I’d expect it to work in similar manner to the object align buttons, where objects are not in alignment (each object is in a different, not ideal state relative to each other) then clicking an align button places them in ideal states).