BFO decision diagram and alignment tool

How to align your domain ontology to a foundational ontology? It’s a well-known question, and one that I’ve looked into before as well. In some of that earlier work, we used DOLCE to align one’s ontology to. We devised the DOLCE decision diagram as part of the FORZA method to assist with the alignment process and implemented that in the MoKI ontology development tool [1]. MoKI is no more, but the theory and the algorithm’s design approach still stand. Instead of re-implementing it as a Protégé plugin and have it go defunct in a few years again (due to incompatible version upgrades, say), it sounded like more fun to design one for BFO and make a stand-alone tool out of it. And that design and the evaluation thereof is precisely what two of my ontology engineering course students—Chiadika Emeruem and Steve Wang—did for their mini-project of the course. That was then finalised and implemented in a tool for general use as part of the DOT4D project extension for my (award-winning) OE textbook afterward.

More precisely, as first part, there’s a diagram specifically for BFO – well, for one of its 2.0-ish versions in existence at least. Deciding on which version to use and what would be good questions was not as trivial as it may sound. While the questions seem to work (as evaluated with several ontologies), it might still be of use to set up an experiment to assess usability from a modeller’s viewpoint.

BFO ‘decision diagram’ to assist trying to align one’s class of a domain or core ontology to BFO (click to enlarge, or navigate to the user guide at https://bfo-classifier.github.io/)

Be this as it may, this decision diagram was incorporated into the tool that wraps around it with a nice interface with user guidance and feedback, and it has the option to load an ontology and save the alignment into the ontology (along with BFO). The decision tree itself is stored as a separate XML file so that it easily can be replaced with any update thereto, be it to reflect changes in question formulation or to adjust it to some later version of BFO. The stand-alone tool is a jar file that can be downloaded from the GitHub repo, and the repo also has the source code that may be used/adapted (i.e., has an open source licence). There’s also a user guide with explanations and screenshots. Here’s another screenshot of the tool in action:

Example of the BFO classifier in use, trying to align CODO’s ‘Disease’ to BFO, the trail of questions answered to get to ‘Disposition’, and the subsumption axiom that can be added to the ontology.

If you have any questions, please feel free to contact either of us.

References

[1] Keet, C.M., Khan, M.T., Ghidini, C. Ontology Authoring with FORZA. 22nd ACM International Conference on Information and Knowledge Management (CIKM’13). ACM proceedings, pp569-578. Oct. 27 – Nov. 1, 2013, San Francisco, USA.

Bias in ontologies?

Bias in models in the area of Machine Learning and Deep Learning are well known. They feature in the news regularly with catchy headlines and there are longer, more in-depth, reports as well, such as the Excavating AI by Crawford and Paglen and the book Weapons of Math Destruction by O’Neil (with many positive reviews). What about other types of ‘models’, like those that are not built in a data-driven bottom-up way from datasets that happen to lie around for the taking, but that are built by humans? Within Artificial Intelligence still, there are, notably, ontologies. I searched for papers about bias in ontologies, but could find only one vision paper with an anecdote for knowledge graphs [1], one attempt toward a framework but looking at FOAF only [2], which is stretching it a little for what passes as an ontology, and then stretching it even further, there’s an old one of mine on bias in relation to conceptual data models for databases [3].

We simply don’t have bias in ontologies? That sounds a bit optimistic since it’s pervasive elsewhere, and at least worthy of examination whether there is such notion as bias in ontologies and if so, what the sources of that may be. And, if one wants to dig deeper, since Ontology: what is bias anyhow? The popular media is much more liberal in the use of the term ‘bias’ than scientific literature and I’m not going to answer that last question here now. What I did do, is try to identify sources of bias in the context of ontologies and I took a relevant selection of Dimara et al’s list of 154 biases [4] (just like only a subset is relevant to their scope) to see whether they would apply to a set of existing ontologies in roughly the same domain.

The outcome of that exploratory analysis [5], in short, is: yes, there is such notion as bias in ontologies as well. First, I’ve identified 8 types of sources, described them, and illustrated them with hand-picked examples from extant ontologies. Second, I examined the three COVID-19 ontologies (CIDO, CODO, COVoc) on possible bias, and they exhibited different subsets indeed.

The sources can be philosophical, by purpose (commonly known as encoding bias), and ‘subject domain’ source, such as scientific theory, granularity, linguistic, social-cultural, political or religious, and economic motivations, and they may be explicit choices or implicit.

Table 1. Summary of typical possible biases in ontologies grouped by source, with an indication whether such biases would be explicit choices or whether they may creep in unintentionally and lead to implicit bias. (Source: [5])

An example of an economic motivation is to (try to) categorise some disorder as a type of disease: there latter gets more resources for medicines, research, treatments and is more costly for insurers who’s rather keep it out of the terminology altogether. Or modifying the properties of a disease or disorder in the classification in the medical ontology so that more people will be categorised as having the disorder even when they don’t. It has happened (see paper for details). Terrorism ontologies can provide ample material for political views to creep in.

Besides the hand-picked examples, I did assess the three COVID-19 ontologies in more detail. Not because I wanted to pick on them—I actually think it’s laudable they tried in trying times—but because they were developed in the same timeframe by three different groups in relative isolation from each other. I looked at both the sources, which can be argued to be present and identified some from a selection of Dimara et al’s list, such as the “mere exposure/familiarity” bias and “false consensus” bias (see table below). How they are present, is also described in that same paper, entitled “An exploration into cognitive bias in ontologies”, which has recently been accepted at the workshop on Cognition And OntologieS V (CAOS’21), which is part of the Joint Ontology Workshops Episode VII at the Bolzano Summer of Knowledge.

Table 2. Tentative presence of bias in the three COVID-19 ontologies, by cognitive bias; see paper for details.

Will it matter for automated reasoning when the ontologies are deployed in various information systems? For reasoning over the TBox only, perhaps not so much, or, at least, any inconsistencies that it would have caused should have been detected and discussed during the ontology development stage, rather.

Will it matter for, say, annotating data or literature etc? Some of it yes, for sure. For instance, COVoc has only ‘male’ in the vocabulary, not female (in line with a well-known issue in evidence-based medicine), so when it is used for the “scientific literature triage” they want to, then it’s going to be even harder to retrieve COVID-19 research papers in relation to women specifically. Similarly, when ontologies are used with data, such as for ontology-based data access, bias may have negative effects. Take as example CIDO’s optimism bias, where a ‘COVID-19 experimental drug in a clinical trial’ is a subclass of ‘COVID-19 drug’, and this ontology would be used for OBDA and data integration, as illustrated in the following use case scenario with actual data from the ClinicalTrials database and the FDA approved drugs database:

Figure 1. OBDI scenario with the CIDO, two database, and a query over the system that returns a logically correct but undesirable result due to some optimism that an experimental substance is already a drug.

The data together with the OBDA-enabled reasoner will return ‘hydroxychloroquine’, which is incorrect and the error is due to the biased and erroneous class subsumption declared in the ontology, not the data source itself.

Some peculiarities of content in an ontology may not be due to an underlying bias, but merely a case of ‘ran out of time’ rather than an act of omission due to a bias, for instance. Or it may not be an honest mistake due to bias but a mistake because of some other reason, such as due to having clicked erroneously on a wrong button in the tool’s interface, say, or having misunderstood the modelling language’s features. Disentangling the notion of bias from attendant ontology quality issues is one of the possible avenues of future work. One also can have a go at those lists and mini-taxonomies of cognitive biases and make a better or more comprehensive one, or to try to harmonise the multitude of definitions of what bias is exactly. Methods and supporting software may also assist ontology developers more concretely further down the line. Or: there seems to be enough to do yet.

Lastly, I still hope that I’ll be allowed to present the paper in person at the CAOS workshop, but it’s increasingly looking less and less likely, as our third wave doesn’t seem to want to quiet down and Italy is putting up more hurdles. If not, I’ll try to make a fancy video presentation.

References

[1] K. Janowicz, B. Yan, B. Regalia, R. Zhu, G. Mai, Debiasing knowledge graphs: Why female presidents are not like female popes, in: M. van Erp, M. Atre, V. Lopez, K. Srinivas, C. Fortuna (Eds.), Proceeding of ISWC 2018 Posters & Demonstrations, Industry and Blue Sky Ideas Tracks, volume 2180 of CEUR-WS, 2017.

[2] D. L. Gomes, T. H. Bragato Barros, The bias in ontologies: An analysis of the FOAF ontology, in: M. Lykke, T. Svarre, M. Skov, D. Martínez-Ávila (Eds.), Proceedings of the Sixteenth International ISKO Conference, Ergon-Verlag, 2020, pp. 236 – 244.

[3] Keet, C.M. Dirty wars, databases, and indices. Peace & Conflict Review, 2009, 4(1):75-78.

[4] E. Dimara, S. Franconeri, C. Plaisant, A. Bezerianos, P. Dragicevic, A task-based taxonomy of cognitive biases for information visualization, IEEE Transactions on Visualization and Computer Graphics 26 (2020) 1413–1432.

[5] Keet, C.M. An exploration into cognitive bias in ontologies. Cognition And OntologieS (CAOS’21), part of JOWO’21, part of BoSK’21. 13-16 September 2021, Bolzano, Italy. (in print)

CLaRO v2.0: A larger CNL for competency questions for ontologies

The avid blog reader with a good memory might remember we had developed a controlled natural language (CNL) in 2019 that we called CLaRO, a Competency question Language for specifying Requirements for an Ontology, model, or specification [1], for specifying requirements on the contents of the TBox (type-level) knowledge specifically. The paper won the best student paper award at the MTSR’19 conference.  Then COVID-19 came along.

Notwithstanding, we did take next steps and obtained some advances in the meantime, which resulted in a substantially extended CNL, called CLaRO v2 [2]. The paper describing how it came about has been accepted recently at the 7th Controlled Natural Language Workshop (CNL2020/21), which will be held on 8-9 September in Amsterdam, The Netherlands, in hybrid mode.

So, what is it about, being “new and improved!” compared to the first version? The first version was created in a bottom-up fashion based on a dataset of 234 competency questions [3] in a few domains only. It turned out alright with decent performance on coverage for unseen questions (88% overall) and very significantly outperforming the others, but there were some nagging doubts about the feasibility of bottom-up approaches to template development, which are essentially at the heart of every bottom-up approach: questions about representativeness and quality of the source data. We used more questions as basis to work from than others and had better coverage, but would coverage improve further then still with even more questions? Would it matter for coverage if the CQs were to come from more diverse subject domains? Also, upon manual inspection of the original CQs, it could be seen that some CQs from the dataset were ill-formed, which propagated through to the final set of templates of CLaRO. Would ‘cleaning’ the source data to presumably better quality templates improve coverage?

One of the PhD students I supervise, Mary-Jane Antia, set out to find answer to these questions. CQs were cleaned and vetted by a linguist, the templates recreated and compared and evaluated—this time automatically in a new testing pipeline. New CQs for ontologies were sourced by searching all over the place and finding some 70, to which we added 22 more variants by tweaking wording of existing CQs such that they still would be potentially answerable by an ontology. They were tested on the templates, which resulted in a lower than ideal percentage of coverage and so new templates were created from them, and yet again evaluated. The key results:

  • An increase from 88% for CLaRO v1 to 94.1% for CLaRO v2 coverage.
  • The new CLaRO v2 has 147 main templates and another 59 variants to cater for minor differences (e.g., singular/plural, redundant words), up from 93 and 41 in CLaRO.
  • Increasing the number of domains that the CQs were drawn from had a larger effect on the CQ coverage than cleaning the source data.
Screenshot of the CLaRO CQ editor tool.

All the data, including the new templates, are available on Github and the details are described in the paper [2]. The CLaRO tool that supports the authoring is in the process of being updated so as to incorporate the v2 templates (currently it is working with the v1 templates).

I will try to make it to Amsterdam where CNL’21 will take place, but travel restrictions aren’t cooperating with that plan just yet; else I’ll participate virtually. Mary-Jane will present the paper, and also for her, despite also having funding for the trip, it increasingly looks like a virtual presentation. On the bright side: at least there is a way to participate virtually.

References

[1] Keet, C.M., Mahlaza, Z., Antia, M.-J. CLaRO: a Controlled Language for Authoring Competency Questions. 13th Metadata and Semantics Research Conference (MTSR’19). 28-31 Oct 2019, Rome, Italy. Springer CCIS vol. 1075, 3-15.

[2]  Antia, M.-J., Keet, C.M. Assessing and Enhancing Bottom-up CNL Design for Competency Questions for Ontologies. 7th International Workshop on Controlled Natural language (CNL’21), 8-9 Sept. 2021, Amsterdam, the Netherlands. (in print)

[3] Potoniec, J., Wisniewski, D., Lawrynowicz, A., Keet, C.M. Dataset of Ontology Competency Questions to SPARQL-OWL Queries Translations. Data in Brief, 2020, 29: 105098.

Toward a framework for resolving conflicts in ontologies (with COVID-19 examples)

Among the many tasks involved in developing an ontologies, are deciding what part of the subject domain to include, and how. This may involve selecting a foundational ontology, reuse of related domain ontologies, and more detailed decisions for ontology authoring for specific axioms and design patterns. A recent example of reuse is that of the Infectious Diseases Ontology for schistosomiasis knowledge [1], but even before reuse, one may have to assess differences among ontologies, as Haendel et al did for disease ontologies [2]. Put differently, even before throwing alignment tools at them or selecting one with an import statement and hope for the best, issues may arise. For instance, two relevant domain ontologies may have been aligned to different foundational ontologies, a partOf relation could be set to be transitive in one ontology but is also used in a qualified cardinality constraint in the other (so then one cannot use an OWL 2 DL reasoner anymore when the ontologies are combined), something like Infection may be represented as a class in one ontology but as a property infectedby in another, or the ontologies differ on the science, like whether Virus is an organism or an inanimate object.

What to do then?

Upfront, it helps to be cognizant of the different types of conflict that may arise, and understand what their causes are. Then one would want to be able to find those automatically. And, most importantly, get some assistance in how to resolve them; if possible, also even preventing conflicts from happening in the first place. This is what Rolf Grütter, from the Swiss Federal Research Institute WSL, and I have been working since he visited UCT last year. The first results have been accepted for the International Conference on Biomedical Ontologies (ICBO) 2020, which are described in a paper entitled “Towards a Framework for Meaning Negotiation and Conflict Resolution in Ontology Authoring” [3]. A sample scenario of the process is illustrated informally in the following figure.

Summary of a sample scenario of detecting and resolving conflicts, illustrated with an ontology reuse scenario where Onto2 will be imported into Onto1. (source: [3])

The paper first defines and illustrates the notions of meaning negotiation and conflict resolution and summarises their main causes, to then go into some detail of the various categories of conflicts and ways how to resolve them. The detection and resolution is assisted by the notion of a conflict set, which is a data structure that stores the details for further processing.

It was tested with a use case of an epizootic disease outbreak in the Lemanic Arc in Switzerland in 2006, due to H5N1 (avian influenza): an administrative ontology had to be merged with one about the epidemiology for infected birds and surveillance zones. With that use case in place already well before the spread of SARS-CoV-2 that caused the current pandemic, it was a small step to add a few examples to the paper about COVID-19. This was made possible thanks to recently developed relevant ontologies that were made available, including for COVID-19 specifically. Let’s highlight the examples here, also so that I can write a bit more about it than the terse text in the paper, since there are no page limits for a blog post.

Example 1: OWL profile violations

Medical terminologies tend to veer toward being represented in an ontology language that is less or equal to OWL 2 EL: this permits scalability, compatibility with typical OBO Foundry ontologies, as well as fitting with the popular SNOMED CT. As one may expect, there have been efforts in ontology development with content relevant for the current pandemic; e.g., the Coronavirus Infectious Disease Ontology (CIDO) [4]. The CIDO is not in OWL 2 EL, however: it has a class expressions with a universal quantifier (ObjectAllValuesFrom) on the right-hand side; specifically (in DL notation): ‘Yale New Haven Hospital SARS-CoV-2 assay’ \sqsubseteq \forall ‘EUA-authorized use at’.’FDA EUA-authorized organization’ or, in the Protégé interface:

(codes: CIDO_0000020, CIDO_0000024, and CIDO_0000031, respectively). It also imported many ontologies and either used them to cause some profile violations or the violations came with them, such as by having used the union operator (‘or’) in the following axiom for therapeutic vaccine function (VO_0000562):

How did I find that? Most certainly NOT by manually browsing through the more than 70000 axioms of the CIDO (including imports) to find the needle in the haystack. Instead, I burned the proverbial haystack to easily get the needles. In this case, the burning was done with the OWL Classifier, which automatically computes which axioms violate any of the OWL species, and lists them accordingly. Here are two examples, illustrating an OWL 2 EL violation (that aforementioned universal quantification) and an OWL 2 QL violation (a property chain with entities from BFO and RO); you can do likewise for OWL 2 RL violations.

Following the scenario with the assumption that the CIDO would have to stay in the OWL 2 EL profile, then it is easy to find the conflicting axioms and act accordingly, i.e., remove them. (It also indicates something did not go well with importing the NDF-RT.owl into the cido-base.owl, but that as an aside for this example.)

Example 2: Modelling issues: same idea, different elements

Let’s take the CIDO again and now also the COviD Ontology for cases and patient information (CODO), which have some overlapping and complementary information, so perhaps could be merged. A not unimportant thing is the test for SARS-CoV-2 and its outcome. CODO has a ‘laboratory test finding’ \equiv {positive, pending, negative}, i.e., the possible outcomes of the test are individuals made into a class using the ObjectOneOf constructor. Consulting CIDO for the test outcomes, it has a class ‘COVID-19 diagnosis’ with three subclasses: Negative, Positive, and Presumptive positive. Aside from the inexact matches of the test status that won’t simplify data integration efforts, this is an example of class vs. instance modeling of what is ontologically the same thing. Resolving this in any merging attempt means that either

  1. the CODO has to change and bump up the test results from individuals to classes, or
  2. the CIDO has to change the subclasses to individuals in the ABox, or
  3. take an ‘outside option’ and represent it in yet a different way where both the CODO and the CIDO have to modify the ontology (e.g., take a conceptual data modeling approach by making the test outcome an attribute with a few possible values).

The paper provides an attempt to systematize such type of conflicts toward a library of common types of conflict, so that it should become easier to find them, and offers steps toward a proper framework to manage all that, which assisted with devising generic approaches to resolution of conflicts. We already have done more to realize all that (which could not all be squeezed into the 12 pages), but more is still to be done, so stay tuned.

Since COVID-19 is still doing the rounds and the international borders of South Africa are still closed (with a lockdown for some 5 months already), I can’t end the blog post with the usual ‘I hope to see you at ICBO 2020 in Bolzano in September’—well, not in the common sense understanding at least. Hopefully next year then.

 

References

[1] Cisse PA, Camara G, Dembele JM, Lo M. An Ontological Model for the Annotation of Infectious Disease Simulation Models. In: Bassioni G, Kebe CMF, Gueye A, Ndiaye A, editors. Innovations and Interdisciplinary Solutions for Underserved Areas. Springer LNICST, vol. 296, 82–91. 2019.

[2] Haendel MA, McMurry JA, Relevo R, Mungall CJ, Robinson PN, Chute CG. A Census of Disease Ontologies. Annual Review of Biomedical Data Science, 2018, 1:305–331.

[3] Grütter R, Keet CM. Towards a Framework for Meaning Negotiation and Conflict Resolution in Ontology Authoring. 11th International Conference on Biomedical Ontologies (ICBO’20), 16-19 Sept 2020, Bolzano, Italy. CEUR-WS (in print).

[4] He Y, Yu H, Ong E, Wang Y, Liu Y, Huffman A, Huang H, Beverley J, Hur J, Yang X, Chen L, Omenn GS, Athey B, Smith B. CIDO, a community-based ontology for coronavirus disease knowledge and data integration, sharing, and analysis. Scientific Data, 2020, 7:181.

A set of competency questions and SPARQL-OWL queries, with analysis

As a good beginning of the new year, our Data in Brief article Dataset of Ontology Competency Questions to SPARQL-OWL Queries Translations [1] was accepted and came online this week, which accompanies our Journal of Web Semantics article Analysis of Ontology Competency Questions and their Formalisations in SPARQL-OWL [2] that was published in December 2019—with ‘our’ referring to my collaborators in Poznan, Dawid Wisniewski, Jedrzej Potoniec, and Agnieszka Lawrynowicz, and myself. The former article provides extensive detail of a dataset we created that was subsequently used for analysis that provided new insights that is described in the latter article.

The dataset

In short, we tried to find existing good TBox-level competency questions (CQs) for available ontologies and manually formulate (i.e., formalise the CQ in) SPARQL-OWL queries for each of the CQs over said ontologies. We ended up with 234 CQs for 5 ontologies, with 131 accompanying SPARQL-OWL queries. This constitutes the first gold standard pipeline for verifying an ontology’s requirements and it presents the systematic analyses of what is translatable from the CQs and what not, and when not, why not. This may assist in further research and tool development on CQs, automating CQ verification, assessing the main query language constructs and therewith language optimisation, among others. The dataset itself is indeed independently reusable for other experiments, and has been reused already [3].

The key insights

The first analysis we conducted on it, reported in [2], revealed several insights. First, a larger set of CQs (cf. earlier work) indeed did increase the number of CQ patterns. There are recurring patterns in the shape of the CQs, when analysed linguistically; a popular one is What EC1 PC1 EC2? obtained from CQs like “What data are collected for the trail making test?” (a Dem@care CQ). Observe that, yes, indeed, we did decouple the language layer from the formalisation layer rather than mixing the two; hence, the ECs (resp. PCs) are not necessarily classes (resp. object properties) in an ontology. The SPARQL-OWL queries were also analysed at to what is really used of that query language, and used most often (see table 7 of the paper).

Second, these characteristics are not the same across CQ sets by different authors of different ontologies in different subject domains, although some patterns do recur and are thus somehow ‘popular’ regardless. Third, the relation CQ (pattern or not) : SPARQL-OWL query (or its signature) is m:n, not 1:1. That is, a CQ may have multiple SPARQL-OWL queries or signatures, and a SPARQL-OWL query or signature may be put into a natural language question (CQ) in different ways. The latter sucks for any aim of automated verification, but unfortunately, there doesn’t seem to be an easy way around that: 1) there are different ways to say the same thing, and 2) the same knowledge can be represented in different ways and therewith leading to a different shape of the query. Some possible ways to mitigate either is being looked into, like specifying a CQ controlled natural language [3] and modelling styles [4] so that one might be able to generate an algorithm to find and link or swap or choose one of them [5,6], but all that is still in the preliminary stages.

Meanwhile, there is that freely available dataset and the in-depth rigorous analysis, so that, hopefully, a solution may be found sooner rather than later.

 

References

[1] Potoniec, J., Wisniewski, D., Lawrynowicz, A., Keet, C.M. Dataset of Ontology Competency Questions to SPARQL-OWL Queries Translations. Data in Brief, 2020, in press.

[2] Wisniewski, D., Potoniec, J., Lawrynowicz, A., Keet, C.M. Analysis of Ontology Competency Questions and their Formalisations in SPARQL-OWL. Journal of Web Semantics, 2019, 59:100534.

[3] Keet, C.M., Mahlaza, Z., Antia, M.-J. CLaRO: a Controlled Language for Authoring Competency Questions. 13th Metadata and Semantics Research Conference (MTSR’19). 28-31 Oct 2019, Rome, Italy. Springer CCIS vol 1057, 3-15.

[4] Fillottrani, P.R., Keet, C.M. Dimensions Affecting Representation Styles in Ontologies. 1st Iberoamerican conference on Knowledge Graphs and Semantic Web (KGSWC’19). Springer CCIS vol 1029, 186-200. 24-28 June 2019, Villa Clara, Cuba. Paper at Springer

[5] Fillottrani, P.R., Keet, C.M. Patterns for Heterogeneous TBox Mappings to Bridge Different Modelling Decisions. 14th Extended Semantic Web Conference (ESWC’17). Springer LNCS vol 10249, 371-386. Portoroz, Slovenia, May 28 – June 2, 2017.

[6] Khan, Z.C., Keet, C.M. Automatically changing modules in modular ontology development and management. Annual Conference of the South African Institute of Computer Scientists and Information Technologists (SAICSIT’17). ACM Proceedings, 19:1-19:10. Thaba Nchu, South Africa. September 26-28, 2017.

Localising Protégé with Manchester syntax into your language of choice

Some people like a quasi natural language interface in ontology development tools, which is why Manchester Syntax was proposed [1]. A downside is that it locks the ontology developer into English, so that weird chimaeras are generated in the interface if the author prefers another language for the ontology, such as, e.g., the “jirafa come only (oja or ramita)” mentioned in an earlier post and that was deemed unpleasant in an experiment a while ago [2]. Those who prefer the quasi natural language components will have to resort to localising Manchester syntax and the tool’s interface.

This is precisely what two of my former students—Adam Kaliski and Casey O’Donnell—did during their mini-project in the ontology engineering course of 2017. A localisation in Afrikaans, as the case turned out to be. To make this publicly available, Michael Harrison brushed up the code a bit and tested it worked also in the new version of Protégé. It turned out it wasn’t that easy to localise it to another language the way it was done, so one of my PhD students, Toky Raboanary, redesigned the whole thing. This was then tested with Spanish, and found to be working. The remainder of the post describes informally some main aspects of it. If you don’t want to read all that but want to play with it right away: here are the jar files, open source code, and localisation instructions for if you want to create, say, a French or Dutch variant.

Some sensible constraints, some slightly contrived ones (and some bad ones), for the purpose of showing the localisation of the interface for the various keywords. The view in English is included in the screenshot to facilitate comparison.

Some sensible constraints, some slightly contrived ones (and some bad ones), for the purpose of showing the localisation of the interface for the various keywords. The view in English is included in the screenshot to facilitate comparison.

The localisation functions as a plugin for Protégé as a ‘view’ component. It can be selected under “Windows – Views – Class views” and then Beskrywing for the Afrikaans and Descripción for Spanish, and dragged into the desired position; this is likewise for object properties.

Instead of burying the translations in the code, they are specified in a separate XML file, whose content is fetched during the rendering. Adding a new ‘simple’ (more about that later) language merely amounts to adding a new XML file with the translations of the Protégé labels and of the relevant Manchester syntax. Here are the ‘simple’ translations—i.e., where both are fixed strings—for Afrikaans for the relevant tool interface components:

 

Class Description

(Label)

Klasbeskrywing

(Label in Afrikaans)

Equivalent To Dieselfde as
SubClass Of Subklas van
General Class axioms Algemene Klasaksiomas
SubClass Of (Anonymous Ancestor) Subklas van (Naamlose Voorvader)
Disjoint With Disjunkte van
Disjoint Union Of Disjunkte Unie van

 

The second set of translations is for the Manchester syntax, so as to render that also in the target language. The relevant mappings for Afrikaans class description keywords are listed in the table below, which contain the final choices made by the students who developed the original plugin. For instance, min and max could have been rendered as minimum and maksimum, but the ten minste and by die meeste were deemed more readable despite being multi-word strings. Another interesting bit in the translation is negation, where there has to be a second ‘no’ since Afrikaans has double negation in this construction, so that it renders it as nie <expression> nie. That final rendering is not grammatically perfect, but (hopefully) sufficiently clear:

An attempt at double negation with a fixed string

An attempt at double negation with a fixed string

Manchester OWL Keyword Afrikaans Manchester OWL

Keyword or phrase

some sommige
only slegs
min ten minste
max by die meeste
exactly precies
and en
or of
not nie <expression> nie
SubClassOf SubklasVan
EquivalentTo DieselfdeAs
DisjointWith DisjunkteVan

 

The people involved in the translations for the object properties view for Afrikaans are Toky, my colleague Tommie Meyer (also at UCT), and myself; snyding for ‘intersection’ sounds somewhat odd to me, but the real tough one to translate was ‘SuperProperty’. Of the four options that were considered—SuperEienskap, SuperVerwantskap, SuperRelasie, and SuperVerband SuperVerwantskap was chosen with Tommie having had the final vote, which is also a semantic translation, not a literal translation.

Screenshot of the object properties description, with comparison to the English

The Spanish version also has multi-word strings, but at least does not do double negation. On the other hand, it has accents. To generate the Spanish version, myself, my collaborator Pablo Fillottrani from the Universidad Nacional del Sur, Argentina, and Toky had a go at it in translating the terms. This was then implemented with the XML file. In case you do not want to dig into the XML file and not install the plugin either, but have a quick look at the translations, they are as follows for the class description view:

 

Class Description

Label

Descripción

(in Spanish)

Equivalent To Equivalente a
SubClass Of Subclase de
General Class axioms Axiomas generales de clase
SubClass Of (Anonymous Ancestor) Subclase de (Ancestro Anónimo)
Disjoint With Disjunto con
Disjoint Union Of Unión Disjunta de
Instances Instancias

 

Manchester OWL Keyword Spanish Manchester OWL Keyword
some al menos uno
only sólo
min al mínimo
max al máximo
and y
or o
not no
exactly exactamente
SubClassOf SubclaseDe
EquivalentTo EquivalenteA
DisjointWith DisjuntoCon

And here’s a rendering of a real ontology, for geo linked data in Spanish, rather than African wildlife yet again:

screenshot of the plugin behaviour with someone else’s ontology in Spanish

One final comment remains, which has to do with the ‘simple’ mentioned above. The approach of localisation presented here works only with fixed strings, i.e., the strings do not have to change depending on the context where it is uses. It won’t work with, say, isiZulu—a highly agglutinating and inflectional language—because isiZulu doesn’t have fixed strings for the Manchester syntax keywords nor for some other labels. For instance, ‘at least one’ has seven variants for nouns in the singular, depending on the noun class of the noun of the OWL class it quantifies over; e.g., elilodwa for ‘at least one’ apple, and esisodwa for ‘at least one’ twig. Also, the conjugation of the verb for the object property depends on the noun class of the noun of the OWL class, but in this case for the one that plays the subject; e.g., it’s “eats” in English for both humans and elephants eating, say, fruit, so one string for the name of the object property, but that’s udla and idla, respectively, in isiZulu. This requires annotations of the classes with ontolex-lemon or a similar approach and a set of rules (which we have, btw) to determine what to do in which case, which requires on-the-fly modifications to Manchester syntax keywords and elements’ names or labels. And then there’s still phonological conditioning to account for. It surely can be done, but it is not as doable as with the ‘simple’ languages that have at least a disjunctive orthography and much less genders or noun classes for the nouns.

In closing, while there’s indeed more to translate in the Protégé interface in order to fully localise it, hopefully this already helps as-is either for reading at least a whole axiom in one’s language or as stepping stone to extend it further for the other terms in the Manchester syntax and the interface. Feel free to extend our open source code.

 

References

[1] Matthew Horridge, Nicholas Drummond, John Goodwin, Alan Rector, Robert Stevens and Hai Wang (2006). The Manchester OWL syntax. OWL: Experiences and Directions (OWLED’06), Athens, Georgia, USA, 10-11 Nov 2016, CEUR-WS vol 216.

[2] Keet, C.M. The use of foundational ontologies in ontology development: an empirical assessment. 8th Extended Semantic Web Conference (ESWC’11), G. Antoniou et al (Eds.), Heraklion, Crete, Greece, 29 May-2 June, 2011. Springer LNCS 6643, 321-335.

[3] Keet, C.M., Khumalo, L. Toward a knowledge-to-text controlled natural language of isiZulu. Language Resources and Evaluation, 2017, 51:131-157. accepted version

Design rationale and overview of the African Wildlife tutorial ontologies

(update 30-7-2020: more details are described in the journal article published in the Journal of Biomedical Semantics)

There are several tutorial ontologies, which typically focus on illustrating one or two aspects of ontology development, notably language features and automated reasoning. This may suffice for one’s aims, but for an ontology engineering course, one would need to be able to illustrate a myriad of development factors and devise exercises for a wider range of tasks of ontology development. For instance, to illustrate the use of ontology design patterns, competency questions, foundational ontologies, and science-based modelling practices, neither of which is addressed easily by the popular tutorial ontologies (notably: wine and pizza), perhaps because they predate most of the advances made in ontology engineering research. Also, I have noticed that my students replicate examples from the exercises they carry out and from inspecting popular and easy-to-find ontologies. Marking the practical assignments, I got to see sandwich and ice cream and burger ontologies with toppings and value partitions, and software and mobile phone ontologies where laptop models are instances rather than classes. Not providing good and versatile examples holistically, causes the propagation of sub-optimal ontology development at least in the exercises, which then also may affect negatively the development of an operational domain ontology that the graduates may have to develop later on.

I’ve been exploring alternatives and variants over the past 11 years in the ontology engineering courses that I have taught yearly to about 8-40 students/year. In an attempt to systematise and possibly generalise from that, I’ve identified 22 requirements that contribute to a good tutorial ontology, which concern the suitability of the subject domain (7 factors), the ease of demonstrating logics and reasoning tasks (7), and assistance with demonstrating engineering aspects (8). Its details are described in a technical report [1]. I don’t claim that it’s an exhaustive list, but that it is one that may help someone to develop their own tutorial ontology in a fun or interesting topic if they so wish—after all, not everyone is interested in pizzas, wines, African wildlife, pets, shirts, a small university, or Robert Stevens’ family.

I’ve tried out a variety of extant tutorial ontologies as well as a range of versions of the African Wildlife Ontology (AWO) over the years (early experiences), eventually settling for a set of 14 versions, all the way from the example from the Primer [2] to DOLCE- and BFO-aligned to translated in several languages, and some with possible answers to some of the exercises. A graphical rendering of the main classes and relations is shown in the following figure:

The versions of the AWO are summarised in the following table, which is also mentioned as annotation in the OWL files.

 

The AWO meets a majority of the 22 requirements, is mature by now, and it has been used yearly in an ontology engineering course or tutorial since 2010. Also, it is links up with my ontology engineering textbook with relevant examples and exercises. The AWO provides a wide range of options concerning examples and exercises for ontology engineering well beyond illustrating only logic features and automated reasoning. For instance, it assists in demonstrating tasks about ontology quality, such as alignment to a foundational ontology and satisfying competency questions, versioning, and multilingual ontologies. For instance, it is easier to demonstrate alignment of a class Animal to DOLCE’s (Non-Agentive) Physical Object than, say, debating what Algorithm aligns with or descend into political debates on the gender binary or what constitutes a family. One can use the height or the colours of the plants and animals to discuss how to model attributes as qualities or dependent entities cf. OWL’s data properties or an artificial ValuePartition. Declare, say, de individual lion simba as an instance of Lion, rather than the confusion regarding grape varieties. Use intuitively obvious disjointness between animals and plants, and subsequently easy catches on sensitising modellers to the far-reaching effects of declaring domain and range axioms by first asserting that animals eat animals, and then adding that carnivorous plants eat insects. In addition, it links up easily to topics for ontology integration activities, such as with biodiversity data, wildlife trade, and tourism to create, e.g., an OBDA system with freely available data (e.g., taken from here) or an ontology-enhanced website for an organisation that offers environmentally sustainable safaris. More examples of broad usage options are described in section 2.3 in the tech report.

The AWO is freely available under a CC-BY licence through the textbook’s webpage at https://people.cs.uct.ac.za/~mkeet/OEbook/ in this folder. A more comprehensive description of the requirements, design, and content is described in a technical report [1] for the time being.

 

References

[1] Keet, CM. The African Wildlife Ontology tutorial ontologies: requirements, design, and content. Technical Report 1905.09519. 23 May 2019. https://arxiv.org/abs/1905.09519.

[2] Antoniou, G., van Harmelen, F. A Semantic Web Primer. MIT Press, USA. 2003.

Tutorial: OntoClean in OWL and with an OWL reasoner

The novelty surrounding all things OntoClean described here, is that we made a tutorial out of a scientific paper and used an example that is different from the (in?)famous manual example to clean up a ‘dirty’ taxonomy.

I’m assuming you have at least heard of OntoClean, which is an ontology-inspired method to examine the taxonomy of an ontology, which may be useful especially when the classes (/universals/concepts/..) have no or only a few properties or attributes declared. Based on that ontological information provided by the modeller, it will highlight violations of ontological principles in the taxonomy so that the ontologist may fix it. Its most recent overview is described in Guarino & Welty’s book chapter [1] and there are handouts and slides that show some of the intermediate steps; a 1.5-page summary is included as section 5.2.2 in my textbook [2].

Besides that paper-based description [1], there have been two attempts to get the reasoning with the meta-properties going in a way that can exploit existing technologies, which are OntOWLClean [3] and OntOWL2Clean [4]. As the names suggest, those existing and widely-used mechanisms are OWL and the DL-based reasoners for OWL, and the latter uses OWL2-specific language features (such as role chains) whereas the former does not. As it happened, some of my former students of the OE course wanted to try the OntoOWLClean approach by Welty, and, as they were with three students in the mini-project team, they also had to make their own example taxonomy, and compare the two approaches. It is their—Todii Mashoko, Siseko Neti, and Banele Matsebula’s—report and materials we—Zola Mahlaza and I—have brushed up and rearranged into a tutorial on OntoClean with OWL and a DL reasoner with accompanying OWL files for the main stages in the process.

There are the two input ontologies in OWL (the domain ontology to clean and the ‘ontoclean ontology’ that codes the rules in the TBox), an ontology for the stage after punning the taxonomy into the ABox, and one after having assigned the meta-properties, so that students can check they did the steps correctly with respect to the tutorial example and instructions. The first screenshot below shows a section of the ontology after pushing the taxonomy into the ABox and having assigned the meta-properties. The second screenshot illustrates a state after having selected, started, and run the reasoner and clicked on “explain” to obtain some justifications why the ontology is inconsistent.

section of the punned ontology where meta-properties have been assigned to each new individual.

A selection of the inconsistencies (due to violating OntoClean rules) with their respective explanations

Those explanations, like shown in the second screenshot, indicate which OntoClean rule has been violated. Among others, there’s the OntoClean rule that (1) classes that are dependent may have as subclasses only those classes that are also dependent. The ontology, however, has: i) Father is dependent, ii) Male is non-dependent, and iii) Father has as subclass Male. This subsumption violates rule (1). Indeed, not all males are fathers, so it would be, at least, the other way around (fathers are males), but it also could be remodelled in the ontology such that father is a role that a male can play.

Let us look at the second generated explanation, which is about violating another OntoClean rule: (2) sortal classes have only as subclasses classes that are also sortals. Now, the ontology has: i) Ball is a sortal, ii) Sphere is a non-sortal, and iii) Ball has as subclass Sphere. This violates rule (2). So, the hierarchy has to be updated such that Sphere is not subsumed by Ball anymore. (e.g., Ball has as shape some Sphere, though note that not all balls are spherical [notably, rugby balls are not]). More explanations of the rule violations are described in the tutorial.

Seeing that there are several possible options to change the taxonomy, there is no solution ontology. We considered creating one, but there are at least two ‘levels’ that will influence what a solution may look like: one could be based on a (minimum or not) number of changes with respect to the assigned meta-properties and another on re-examining the assigned meta-properties (and then restructuring the hierarchy). In fact, and unlike the original OntoClean example, there is at least one case where there is a meta-property assignment that would generally be considered to be wrong, even though it does show the application of the OntoClean rule correctly. How best to assign a meta-property, i.e., which one it should be, is not always easy, and the student is also encouraged to consider that aspect of the method. Some guidance on how to best modify the taxonomy—like Father is-a Male vs. Father inheres-in some Male—may be found in other sections and chapters of the textbook, among other resources.

 

p.s.: this tutorial is the result of one of the activities to improve on the OE open textbook, which are funded by the DOT4D project, as was the tool to render the axioms in DL in Protégé. A few more things are in the pipeline (TBC).

 

References

[1] Guarino, N. and Welty, C. A. (2009). An overview of OntoClean. In Staab, S. and Studer, R., editors, Handbook on Ontologies, International Handbooks on Information Systems, pages 201-220. Springer.

[2] Keet, C. M. (2018). An introduction to ontology engineering. College Publications, vol 20. 344p.

[3] Welty, C. A. (2006). OntOWLClean: Cleaning OWL ontologies with OWL. In Bennett, B. and Fellbaum, C., editors, Proceedings of the Fourth International Conference on Formal Ontology in Information Systems (FOIS 2006), Baltimore, Maryland, USA, November 9-11, 2006, volume 150 of Frontiers in Artificial Intelligence and Applications, pages 347-359. IOS Press.

[4] Glimm, B., Rudolph, S., Volker, J. (2010). Integrated metamodeling and diagnosis in OWL 2. In Peter F. Patel-Schneider, Yue Pan, Pascal Hitzler, Peter Mika, Lei Zhang, Je_ Z. Pan, Ian Horrocks, and Birte Glimm, editors, Proceedings of the 9th International Semantic Web Conference, LNCS vol 6496, pages 257-272. Springer.

About modelling styles in ontologies

As any modeller will know, there are pieces of information or knowledge that can be represented in different ways. For instance, representing ‘marriage’ as class or as a ‘married to’ relationship, adding ‘address’ as an attribute or a class in one’s model, and whether ‘employee’ will be positioned as a subclass of ‘person’ or as a role that ‘person’ plays. In some cases, there a good ontological arguments to represent it in one way or the other, in other cases, that’s less clear, and in yet other cases, efficiency is king so that the most compact way of representing it is favoured. This leads to different design decisions in ontologies, which hampers ontology reuse and alignment and affects other tasks, such as evaluating competency questions over the ontology and verbalising ontologies.

When such choices are made consistently throughout the ontology, one may consider this to be a modelling style or representation style. If one then knows which style an ontology is in, it would simplify use and reuse of the ontology. But what exactly is a representation style?

While examples are easy to come by, shedding light on that intuitive notion turned out to be harder than it looked like. My co-author Pablo Fillottrani and I tried to disentangle it nonetheless, by characterising the inherent features and the dimensions by which a style may differ. This resulted in 28 different traits for the 10 identified dimensions.  For instance, the dimension “modular vs. monolithic” has three possible options: 1) ‘Monolithic’, where the ontology is stored in one file (no imports or mergers); 2) ‘Modular, external’, where at least one ontology is imported or merged, and it kept its URI (e.g., importing DOLCE into one’s domain ontology, not re-creating it there); 3) ‘Modular, internal’, where there’s at least one ontology import that’s based on having carved up the domain in the sense of decomposition of the domain (e.g., dividing up a domain into pizzas and drinks at pizzerias).  Other dimensions include, among others, the granularity of relations (many of few), how the hierarchy looks like, and attributes/data properties.

We tried to “eat our own dogfood” and applied the dimensions and traits to a set of 30 ontologies. This showed that it is feasible to do, although we needed two rounds to get to that stage—after the first round of parallel annotation, it turned out we had interpreted a few traits differently, and needed to refine the number of traits and be more precise in their descriptions (which we did). Perhaps unsurprising, some tendencies were observed, and we could identify three easily recognisable types of ontologies because most ontologies had clearly one or the other trait and similar values for sets of trait. Of course, there were also ontologies that were inherently “mixed” in the sense of having applied different and conflicting design decisions within the same ontology, or even included two choices. Coding up the results, we generated two spider diagrams that visualise that difference. Here’s one:

Details of the dimensions, traits, set-up and results of the evaluation, and discussion thereof have been published this week [1] and we’ll present it next month at the 1st Iberoamerican Conference on Knowledge Graphs and Semantic Web (KGSWC’19), in Villa Clara, Cuba, alongside 13 other papers on ontologies. I’m looking forward to it!

 

References

[1] Keet, C.M., Fillottrani, P.R.. Dimensions Affecting Representation Styles in Ontologies. 1st Iberoamerican conference on Knowledge Graphs and Semantic Web (KGSWC’19). Springer CCIS vol 1029, 186-200. 24-28 June 2019, Villa Clara, Cuba. Paper at Springer

An Ontology Engineering textbook

My first textbook “An Introduction to Ontology Engineering” (pdf) is just released as an open textbook. I have revised, updated, and extended my earlier lecture notes on ontology engineering, amounting to about 1/3 more new content cf. its predecessor. Its main aim is to provide an introductory overview of ontology engineering and its secondary aim is to provide hands-on experience in ontology development that illustrate the theory.

The contents and narrative is aimed at advanced undergraduate and postgraduate level in computing (e.g., as a semester-long course), and the book is structured accordingly. After an introductory chapter, there are three blocks:

  • Logic foundations for ontologies: languages (FOL, DLs, OWL species) and automated reasoning (principles and the basics of tableau);
  • Developing good ontologies with methods and methodologies, the top-down approach with foundational ontologies, and the bottom-up approach to extract as much useful content as possible from legacy material;
  • Advanced topics that has a selection of sub-topics: Ontology-Based Data Access, interactions between ontologies and natural languages, and advanced modelling with additional language features (fuzzy and temporal).

Each chapter has several review questions and exercises to explore one or more aspects of the theory, as well as descriptions of two assignments that require using several sub-topics at once. More information is available on the textbook’s page [also here] (including the links to the ontologies used in the exercises), or you can click here for the pdf (7MB).

Feedback is welcome, of course. Also, if you happen to use it in whole or in part for your course, I’d be grateful if you would let me know. Finally, if this textbook will be used half (or even a quarter) as much as the 2009/2010 blogposts have been visited (around 10K unique visitors since posting them), that would mean there are a lot of people learning about ontology engineering and then I’ll have achieved more than I hoped for.

UPDATE: meanwhile, it has been added to several open (text)book repositories, such as OpenUCT and the Open Textbook Archive, and it has been featured on unglue.it in the week of 13-8 (out of its 14K free ebooks).