Do robot snooker players dream of semantic frames?

As a result of the development of the kungkhies project [1,2] it has been discovered that intended learning outcomes (ILOs) can be formalized using the concept of semantic frames. This leads one to wonder how frames might be used to describe the academic curriculum rather than just the ILOs associated with a particular course. The advantage in doing this is that semantic frames naturally form a network that can represent relationships between curriculum content items better than the conventional method which is essentially to provide a list of statements.

A semantic frame is an information (or data) structure that describes an event, situation, concept, state of affairs, process or any other entity about which an information structure can be clearly individuated. The FrameNet project [3] has established a network of 1160 English language semantic frames. For example, the Giving frame has core frame elements of Donor, Recipient and Theme (the object given). In order to extend the semantic richness to cover usage in English language texts, additional non-core elements such as Circumstances, Manner and Means are also associated with the frame.

Putting FrameNet together has been an enormous task involving the hand-annotation of tens of thousands  of sentences from corpora. Whereas there are a handful of frames in FrameNet that are chemistry-related such as Thermodynamic_phase and Change_of_phase, a great deal of work would be required to extend the net to cover the knowledge represented by even a basic chemistry syllabus.

A good example of the difficulty involved in creating frames can be found at the first step. The most fundamental of chemistry frames must describe the meaning of the basic objects of chemistry - atoms, molecules and stuff in jars.

Let us go to the International Union of Pure and Applied Chemistry (IUPAC) for some initial guidance on meaning and look at their Gold Book [4], a compendium of chemical nomenclature compiled from various standards documents.

The terms that they define to describe the basic building blocks of chemistry are chemical substance, chemical species, chemical species of an element, molecular entity, atom and molecule.

The difficulties here are to distinguish between classes of entities and individual instances, and to distinguish between bulk quantities and individual microscopic units.

First take the classes: chemical substance, chemical species (include chemical species of an element as a subclass here)  and molecular entity.

The three Gold Book definitions are as follows.

chemical substance

Matter of constant composition best characterized by the entities (molecules, formula units, atoms) it is composed of. Physical properties such as density, refractive index, electric conductivity, melting point etc. characterize the chemical substance.

chemical species

An ensemble of chemically identical molecular entities that can explore the same set of molecular energy levels on the time scale of the experiment. The term is applied equally to a set of chemically identical atomic or molecular structural units in a solid array. For example, two conformational isomers may be interconverted sufficiently slowly to be detectable by separate NMR spectra and hence to be considered to be separate chemical species on a time scale governed by the radiofrequency of the spectrometer used. On the other hand, in a slow chemical reaction the same mixture of conformers may behave as a single chemical species, i.e. there is virtually complete equilibrium population of the total set of molecular energy levels belonging to the two conformers. Except where the context requires otherwise, the term is taken to refer to a set of molecular entities containing isotopes in their natural abundance. The wording of the definition given in the first paragraph is intended to embrace both cases such as graphite, sodium chloride or a surface oxide, where the basic structural units may not be capable of isolated existence, as well as those cases where they are. In common chemical usage generic and specific chemical names (such as radical or hydroxide ion) or chemical formulae refer either to a chemical species or to a molecular entity.

chemical species of an element

Specific form of an element defined as to isotopic composition, electronic or oxidation state, and/or complex or molecular structure. 

 molecular entity

Any constitutionally or isotopically distinct atom, molecule, ion, ion pair, radical, radical ion complex, conformer etc., identifiable as a separately distinguishable entity.Molecular entity is used in this glossary as a general term for singular entities,irrespective of their nature, while chemical species stands for sets or ensembles of molecular entities. Note that the name of a compound may refer to the respective molecular entity or to the chemical species, e.g. methane, may mean a single molecule of CH, (molecular entity) or a molar amount, specified or not (chemical species), participating in a reaction. The degree of precision necessary to describe a molecular entity depends on the context. For example "hydrogen molecule" is an adequate definition of a certain molecular entity for some purposes, whereas for others it is necessary to distinguish the electronic state and/or vibrational state and/or nuclear spin, etc. of the hydrogen molecule.

The first difficulty is that IUPAC's definition of chemical species is at odds with common usage.  In the daily life of a chemist it is used to categorize. One refers to a free radical reaction, for example, as having, say, 5 species involved, meaning 5 radicals of differing chemical constituency. [Note added April 2013: the handling of chemical species is described in https://code.google.com/p/mean-mythic-ferrets/wiki/ChemicalSpecies/ essentially the IUPAC definition together with the introduction of aomic chemical entities.]

And IUPAC defines a chemical element as

A species of atoms; all atoms with the same number of protons in the atomic nucleus.

This is not an ensemble. This reads like a species is a universal set.

The Chemical Information Ontology [5] does not use the term chemical species at all and has chemical entity as the top-level entry. Subclasses of this are molecular entity and chemical substance (the ensemble term).

The primary focus of the Chemical Information Ontology is chemical data rather than creating some sort of curricular knowledge base, and so it is not surprising that its classifications do not fit precisely the needs found here. For example, the meaning of molecular entity is retained to refer to both atomic and molecular objects. For curricular purposes, an atomic entity needs to be introduced.

And so, as a starting point, take ChemicalEntity as the base frame for chemical objects, which is inherited by AtomicChemicalEntity and MolecularChemicalEntity.

ChemicalSubstance will pertain to chemical objects to which the property amount applies, that is, bulk or ensemble quantities.

There will also be corresponding cardinality frames applying to specific atoms. For example, it is possible to use atomic force microscopes to manoeuvre individual atoms on an underlying surface. A cardinality frame would apply here to refer to atoms in a particular experiment.

The aim of the Mean Mythic Ferrets project is to create a semantic frame network for an A level chemistry curriculum.

References

1. kungkhies, http://code.google.com/p/kungkhies/
2. Canonilo, http://code.google.com/p/canonilo/
3. FrameNet, https://framenet.icsi.berkeley.edu/fndrupal/home
4. Gold Book, http://goldbook.iupac.org/index.html
5. Chemical Information Ontology, http://code.google.com/p/semanticchemistry/

After completing this blog, an assessment body will be able to...

...write effective intended learning outcomes.

As part of the Canonilo project, over 3000 chemistry-related intended learning outcomes (ILOs) were harvested from miscellaneous sources on the Web, but mainly from the specifications documents of the UK assessment boards for A-level and GCSE chemistry. Whilst the aim was to analyse these for syntactical and semantic structure, it was difficult not to notice how poorly many of the ILOs were expressed.

There are literally hundreds of guides on the Web on how to write good ILOs. Almost all of them make the recommendation that verb constructions such as understand..., understand that..., have an understanding of..., show an awareness of..., have an appreciation of... are to be avoided.

This advice is well-founded. Without going in to too much detail, the aim of using ILOs is essentially to maximise the common ground between teacher and student in the knowledge that they consider should be gained at the completion of a course of instruction.

The verb constructions mentioned above do not maximise the common ground. Student and teacher will not have a clear idea about what the other means by the expression understand that...

Hence the fact that ILOs should have at their heart dynamic verbs such as describe, define, state, list, calculate, and the rest of the usual suspects. The knowledge that a student must attain is now much clearer - it is the knowledge that enables him or her to describe, define, state, list and calculate...

Not all of the sources of the specification documents - AQA, CIE, CCEA, OCR, WJEC - were equally culpable. Some were very much better than others. However, one A-level specification document had around 30% of its ILOs starting with the verb understand: Understand the concept of..., Understand the importance of..., Understand how..., Understand that..., Understand qualitatively how...

The chemistry students involved are not being best served by this state of affairs.