BPs sorted left are tagged with the keyword "abstract" on the OEBP. The solution is not an easily-checked or concretely-defined geometrical or numerical property in pictures.

Adjacent-numbered pages:
BP507 BP508 BP509 BP510 BP511  *  BP513 BP514 BP515 BP516 BP517

abstract, meta (see left/right), links, keyword, left-self, sideless

bp [smaller | same | bigger]

Aaron David Fairbanks

Left examples have the keyword "leftright" on the OEBP.

See updown.

All "leftright" Bongard Problems are handed.

Adjacent-numbered pages:
BP530 BP531 BP532 BP533 BP534  *  BP536 BP537 BP538 BP539 BP540

meta (see left/right), links, keyword, sideless, invariance

handed_visualbp [smaller | same | bigger]

Aaron David Fairbanks

Bongard Problems sorted left have the keyword "meta" on the OEBP.

Meta Bongard Problems are Bongard Problems that sort Bongard Problems. Sometimes abbreviated MBPs.

The first meta Bongard Problem was BP200.

Some meta BP pages sort images of Bongard Problems (keyword miniproblems), while other meta BP pages sort other BP pages (keyword links).

BPs that sort meta-BPs are labelled metameta.

Adjacent-numbered pages:
BP532 BP533 BP534 BP535 BP536  *  BP538 BP539 BP540 BP541 BP542

meta (see left/right), links, keyword, world, left-self, sideless, metameta, left-full, feedback

bp [smaller | same | bigger]
zoom in left (linksbp)

Aaron David Fairbanks

Left examples have the keyword "handed" on the OEBP.

If mirroring any example along the any axis can change its sorting the BP is "handed."

Note that BPs about comparing orientation between multiple things in one example fit on the right side.

See BP871 for the version with pictures of Bongard Problems (miniproblems) instead of links to pages on the OEBP.

The keyword leftright is specifically about flipping over the vertical axis, while the keyword updown is specifically about flipping over the horizontal axis.

Bongard Problems tagged rotate are usually "handed", since any rotation can be created by two reflections. Not necessarily, however, since the reflected step in between might not be sorted on either side by the Bongard Problem.

Adjacent-numbered pages:
BP547 BP548 BP549 BP550 BP551  *  BP553 BP554 BP555 BP556 BP557

meta (see left/right), links, keyword, invariance, wellfounded

visualbp [smaller | same | bigger]
zoom in left (handed_visualbp)

Aaron David Fairbanks

Left examples have the keyword "structure" on the OEBP.

Examples of "structures": Bongard Problem, Bongard Problem with extra unsorted panel ("Bongard's Dozen"), 4-panel analogy grid, sequence of objects with a quantity changing by a constant amount.

If the solver hasn't become familiar with the featured structure, the Bongard Problem's solution may seem convoluted or inelegant. (See keyword assumesfamiliarity.) Once the solver gets used to seeing a particular structure it becomes easier to read that structure and solve Bongard Problems featuring it.

A Bongard Problem can non-verbally teach someone how a particular structure works, showing valid examples of that structure versus non-examples. E.g., BP968 for the structure of Bongard Problems and BP981 for the structure of analogy grids.

Adjacent-numbered pages:
BP784 BP785 BP786 BP787 BP788  *  BP790 BP791 BP792 BP793 BP794

meta (see left/right), links, keyword

bp [smaller | same | bigger]

Aaron David Fairbanks

Left-sorted Bongard Problems have the keyword "creativeexamples" on the OEBP.

Be encouraged to contribute new interesting examples to Bongard Problems with this keyword.

There is much overlap with the keyword hardsort.

This is what it usually means to say examples fit on (e.g.) the left of a Bongard Problem in various creative ways: there is no (obvious) general method to determine a left-fitting example fits left.

There is a related idea in computability theory: a "non recursively enumerable" property is one that cannot in general be checked by a computer algorithm.

But keep in mind the tag "creativeexamples" is supposed to mean something less formal. For example, it requires no ingenuity for a human being to check when a simple shape is convex or concave (so BP4 is not labelled "creativeexamples"). However, it is not as if we use an algorithm to do this, like a computer. (It is not even clear what an "algorithm" would mean in this context, since it is ambiguous both what class of shapes the Bongard Problem sorts and how that would be encoded into a computer program's input. There are usually many options and ambiguities like this whenever one tries to formalize the content of a Bongard Problem.)

Adjacent-numbered pages:
BP861 BP862 BP863 BP864 BP865  *  BP867 BP868 BP869 BP870 BP871

notso, meta (see left/right), links, keyword

bp [smaller | same | bigger]

Aaron David Fairbanks

Left-sorted Bongard Problems have the keyword "assumesfamiliarity" on the OEBP.

Sometimes all the examples in a Bongard Problem need to be interpreted a certain way for the Bongard Problem to make sense. Only once the representation is understood, the idea seems simple.

For example, all meta Bongard Problems (Bongard Problems sorting other Bongard Problems) assume the solver interprets the examples as Bongard Problems.

TO DO: Maybe it is best to stop putting the label "assumesfamiliarity" on all meta-Bongard Problems. There are so many of them. It may be better to only use the "assumesfamiliarity" keyword on meta-BPs for a further assumption than just that all examples are interpreted as Bongard Problems. - Aaron David Fairbanks, Feb 11 2021

Many Bongard Problems in which all examples take the same format (keyword structure) assume the solver already knows how to read that format.

Some Bongard Problems assume the solver will be able to understand symbolism that is consistent between examples (keyword consistentsymbols).

Bongard Problems tagged math often assume the solver is familiar with a certain representation of a math idea.

Adjacent-numbered pages:
BP1106 BP1107 BP1108 BP1109 BP1110  *  BP1112 BP1113 BP1114 BP1115 BP1116

BP1032: The solution should really read "Assuming all images are Bongard Problems sorting each natural number left or right ..." This Bongard Problem makes sense to someone who has been solving a series of similar BPs, but otherwise there is no reason to automatically read a collection of numbers as standing for a larger collection of numbers.

fuzzy, meta (see left/right), links, keyword

bp [smaller | same | bigger]

Aaron David Fairbanks