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Add forall() tutorial and example and index - #165
juliannab-5 wants to merge 4 commits into
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| pr.add_rule( | ||
| pr.Rule( | ||
| "ViewedByAll(y) <- HaveAccess(x,y), Viewed(x)", |
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This version doesn't use forall(), so the tutorial's "full code" link points to a file that doesn't use the feature. Look at the example Colton did, you can build from it instead of making a new different file
| PyReason Forall Functionality | ||
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| In this tutorial, we will look at how to utilize the forall function in a knowledge graph. The rule will fire only when all of the groundings of a given clause are true. |
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It would help to say what a grounding is here, since the tutorial relies on the word. For example: "In this example, the groundings of x are the people who have access to the message."
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| The ``head`` of the rule is ``ViewedByAll(y)`` and the body is ``HaveAccess(x,y), forall(Viewed(x))``. The head and body are separated by an arrow which means the rule will start evaluating from | ||
| timestep ``0``. |
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The arrow <- means the head is inferred in the same timestep the body holds. <-1 would infer it one timestep later. It doesn't set when evaluation starts
| The ``head`` of the rule is ``ViewedByAll(y)`` and the body is ``HaveAccess(x,y), forall(Viewed(x))``. The head and body are separated by an arrow which means the rule will start evaluating from | ||
| timestep ``0``. | ||
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| ``Viewed(x)`` checks to see if each grounding of ``x`` is true (or in this case has viewed the message). By wrapping the clause in ``forall(...)`` it fires only once all the groundings are true (in this case viewed the message). |
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This is the key part of the tutorial, so it's worth showing what forall changes. Without forall, the same rule fires at t=0, because by default one satisfying grounding is enough (Zach and Justin view at t=0). With forall it waits until t=2. A short "without forall" snippet with its output would make that clear. You could also mention that forall behaves the same as custom thresholds of number >= 1 and percent total >= 100, and link to custom_thresholds_tutorial as reference
| In our case we want one person to view the ``TextMessage`` at a particular timestep. | ||
| For example, we create facts stating: | ||
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| - ``Zach`` and ``Justin`` view the ``TextMessage`` from at timestep ``0`` |
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I would say at timestep 0 instead of "from at timestep 0"
| - ``Zach`` and ``Justin`` view the ``TextMessage`` from at timestep ``0`` | ||
| - ``Michelle`` views the ``TextMessage`` at timestep ``1`` | ||
| - ``Amy`` views the ``TextMessage`` at timestep ``2`` | ||
| - ``3`` is the last timestep the rule is active for all. |
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3 is the end time of the facts, meaning each Viewed fact holds until timestep 3
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| .. code:: python | ||
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| # Run the program for three timesteps to see the forall(..) function fire |
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This runs through timestep 3, so the output shows four timesteps (0 to 3). Maybe say "run until timestep 3"
| print() | ||
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| This specifies how many timesteps to run for. | ||
| This formats the output to display the filtered node and edge data. |
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These two sentences feel incomplete, maybe merge them into one line explaining the reason call and the output loop
| 1. For timestep 0, we set ``Zach -> Viewed: [1,1]`` and ``Justin -> Viewed: [1,1]`` in the facts | ||
| 2. For timestep 1, ``Michelle`` views the TextMessage as stated in facts ``Michelle -> Viewed: [1,1]``. | ||
| 3. For timestep 2, since ``Amy`` has just viewed the ``TextMessage``, therefore ``Amy -> Viewed: [1,1]``. As per the rule, | ||
| since all the people have viewed the ``TextMessage``, the message is marked as ``ViewedByAll``. |
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Could you say explicitly that t=2 is the first timestep where every grounding holds, which is why forall fires there? And add a line for timestep 3: it's still ViewedByAll because the Viewed facts hold through t=3
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This was the tutorial for the forall() quantifier. I used Colton's example in the documentation.