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Intelligent Content

Key Verbs: Actions in Taxonomies

When authors tell stories, verbs provide the action. Verbs move audiences. We want to know “what happened next?” But verbs are hard to categorize in ways computers understand and can act on. Despite that challenge, verbs are important enough that we must work harder to capture their intent, so we can align content with the needs of audiences. I will propose two approaches to overcome these challenges: task-focused and situational taxonomies. These approaches involve identifying the “key verbs” in our content.

Nouns and Verbs in Writing

I recently re-read a classic book on writing by Sir Ernest Gowers entitled The Complete Plain Words. Published immediately after the Second World War, the book was one of the first to advocate the use of plain language.

Gowers attacks obtuse, abstract writing. He quotes with approval a now forgotten essayist G.M. Young:

“Excessive reliance on the noun at the expense of the verb will in the end detach the mind of the writer from the realities of here and now, from when and how, and in what mood this thing was done and insensibly induce a habit of abstraction, generalization and vagueness.”

If we look past the delicious irony — a critique of abstraction that is abstract — we learn that writing that emphasizes verbs is vivid.

Gowers refers to this snippet as an example of abstract writing:

  • “Communities where anonymity in personal relationships prevails.”

Instead, he says the wording should be:

  • “Communities where people do not know one another.”

Without doubt the second example is easier to read, and feels more relevant to us as individuals. But the meaning of the two sentences, while broadly similar, is subtly different. We can see this by diagramming the key components. The strengthening of the verb in the second example has the effect of making the subject and object more vague.

role of verb in sentence

It is easy to see the themes in the first example, which are explicitly called out. The first diagram highlights themes of anonymity and personal relationships in a way the second diagram does not. The different levels of detail in the wording will draw attention to different dimensions.

With a more familiar style of writing, the subject is often personalized or implied. The subject is about you, or people like you. This may be one reason why lawyers and government officials like to use abstract words. They aren’t telling a specific story; they are trying to make a point about a more general concept.

Abstract vs Familiar Styles

I will make a simple argument. Abstract writing focuses on nouns, which are easier for computers to understand. Conversely, content written in a familiar style is more difficult for computers to understand and act on. Obviously, people — and not computers — are the audience for our content. I am not advocating an abstract style of writing. But we should understand and manage the challenges that familiar styles of writing pose for computers. Computers do matter. Until natural language processing by computers truly matches human abilities, humans are going to need to help computers understand what we mean. Because it’s hard for computers to understand discussions about actions, it is even more important that we have metadata that describes those actions.

The table below summarizes the orientations of each style. These sweeping characterizations won’t be true in all cases. Nonetheless, these tendencies are prevalent, and longstanding.

Abstract Style Familiar Style
Emphasis
  • Nouns
  • General concepts
  • Reader is outside of the article context
  • Verbs
  • Specific advice
  • Reader is within the article context
Major uses
  • Represents a class of concepts or events
  • Good for navigation
  • Shows instance of a concept or event
  • Good for reading
Benefits
  • Promotes analytic tracking
  • Promotes automated content recommendations
  • Promotes content engagement
  • Promotes social referrals
Limitations
  • Can trigger weak writing
  • Can trigger weak metadata

These tendencies are not destiny. Steven Pinker, the MIT cognitive scientist turned prose guru, can write about abstract topics in an accessible manner — he makes an effort to do so. Likewise, it is possible to develop good metadata for narrative content. It requires the ability to sense what is missing and implied.

Challenges of a Taxonomy of Verbs

Why is metadata difficult for narrative content? Why is so much metadata tilted toward abstract content? There are three main issues:

  • Indexing relies on basic vocabulary matching
  • Taxonomies are noun-centric
  • Verbs are difficult to specify

Indexing and Vocabulary Matching

Computers rely on indexes to identify content. Metadata is a type of index that identifies and describes the content. Metadata indexes may be based the manual tagging of content (application of metadata) with descriptive terms, or be based on auto-indexing and auto-categorization.

Computers can easily identify and index nouns, often referred to as entities. Named entity recognition can identify proper nouns such as personal names. It is also comparatively easy to identify common nouns in a text when a list of nouns of interest has been identified ahead of time. This is done either through string indexing (matching the character string to the index term) or assigned indexing (matching a character string to a concept term that has been identified as equivalent.)

The manual tagging of entities is also straightforward. A person will identify the major nouns used in a text, and select the appropriate index term that corresponds to the noun. When they decide what things are most important in the article (often the things mentioned most frequently), they find tags that describe those things.

When the text has entities that are proper or common nouns, it isn’t too hard to identify which ones are important and should be indexed. Abstract content is loaded with such nouns, and computers (and people) have an easy time identifying key words that describe the content. But as we will see, when the meaning of a text is based on the heavy use of pronouns and descriptive verbs, the task of matching terms to an index vocabulary becomes more difficult. Narrative content, where verbs are especially important to the meaning, is challenging to index. Nouns are easier to decipher than verbs.

Taxonomies are Noun-centric

When we offer a one-word description, we tend to label stuff using nouns. The headings in an encyclopedia are nouns. Taxonomies similarly rely on nouns to identify what an article is about. It’s our default way of thinking about descriptions.

Because we focus on the nouns, we can easily overlook the meaning carried by the verbs when tagging our content. But verbs can carry great meaning. Consider an article entitled “How to feel more energetic.” There are no nouns in the title to match up with taxonomy terms. Depending on the actual content of the article, it might relate to exercise, or diet, or mental attitude, but those topics are secondary in purpose to the theme of the article, which is about feeling better. A taxonomy may have granular detail, and include a thesaurus of equivalent and related terms, but the most critical issue is that the explicit wording of the article can be translated into the vocabulary used in the taxonomy.

Verbs are Difficult to Specify

Verbs also can be included in descriptive vocabularies for content, but they are more challenging to use. Verbs are sometimes looser in meaning than nouns. Sometimes they are figurative.

graph of verb definition
Verbs such as to make can have many different meanings

A verb may have many meanings. These meanings are sometimes fuzzy. Actions and sentiments can be described by multiple verbs and verbal phrases. Consider the most overworked and meaningless verb used on the web today: to like. If Ralph “likes” this, what does that really mean? Compared to what else? The English language has a range of nuanced verbs (love, being fond of, being interested in, being obsessed with, etc.) to express positive sentiment, though it is hard to demarcate their exact equivalences and differences.

Many common verbs (such as work, make or do) have a multitude of meanings. When the meaning of a verbs is nebulous, it is takes more work to identify the preferred synonym used in a taxonomy. Consider this example from a text-tagging tool. The person reading the text needs to make the mental leap that the verb “moving” refers to “money transfer.” The task is not simply to match a word, but to represent a concept for an activity. We often use imprecise verb like move instead of more precise verb like transfer money. Such verbal informality makes tagging more difficult.

Tagging a verb with a taxonomy term.  Screenshot via Brat.
Tagging a verb with a taxonomy term. Screenshot via Brat.

With the semantic web, predicates play the role of verbs defining the relationship between subjects and objects. The predicates can have many variants to express related concepts. If we say, “Jane Blogs was formerly married to Joe Blogs,” we don’t know what other verbal phrase would be equivalent. Did Jane Blogs divorce Joe Blogs? Did Joe Blogs die? Another piece of information may be needed to infer the full meaning. Verbal phrases can carry a degree of ambiguity, and this makes using a standard vocabulary for verbs harder to do.

Samuel Goto, a software engineer at Google, has said: “Verbs … they are kind of weird.”

Computers can’t understand verbs easily. Verb concepts are challenging for humans to describe with standardized vocabulary. Tagging verbs requires thought.

Why Verb Metadata Matters

If verbs are a pain to tag, why bother? So we can satisfy both the needs of our audiences and the needs of the computers that must be able to offer our audiences precisely what they want. As an organization, we need to make sure all this is happening effectively. We need to harmonize three buckets of needs: audience, IT, and brand.

Audience needs: Most audiences expect content written in familiar style, and want content with strong, active verbs. Those verbs often carry a big share of the meaning of what you are communicating. Audiences also want precise content, rather than hoping to stumble on something they like by accident. This requires good metadata.

IT needs: Computers have trouble understanding the meaning of verbs. Computers need a good taxonomy to support navigation through the content, and deliver good recommendations.

Brand needs: Brands need to be able to manage and analyze content according to the activities discussed in the content, not just the static nouns mentioned in it. If they don’t have a plan in place to identify key verbs in their content, and tag their meaning, they run the risk of having a hollow taxonomy that doesn’t deliver the results needed.

A solution to these competing needs is to have our metadata represent the actions mentioned in the content. I’m calling this approach finding your key verbs.[1]

Approaches to a Metadata of Actions

Two approaches are available to represent verb concepts. The first is to make verbs part of your taxonomy. The second is to translate verbs in your content into nouns in your taxonomy.

Task-focused Taxonomies

The first approach is to develop a list of verbs that express the actions discussed in your content. Starting with the general topics about which you produce content, you can do an analysis and see what specific activities the content discusses. We’ll call these activities “tasks.”

Think about the main tasks for the people we want to reach. How do they talk about these tasks? People don’t label themselves as a new-home buyer: they are looking for a new home. They may never actually buy, but they are looking. Verbs help us focus on what the story is. There may be sub tasks that our reader would do, and would want to read about. Not only are they looking for a new home, they are evaluating kitchens and getting recommendations on renovations. This task focus is important to help us manage content components, and track their value to audience segments. We can do this using a task-focused taxonomy.

I am aware of two general-purpose taxonomies that incorporate verbs. The tasks these taxonomies address may differ from your needs, but they may provide a starting point for building your own.

The new “actions” vocabulary available in schema.org is the better known of the two. Schema.org has identified around 100 actions “to describe what can be done with resources.” The purpose is to be able not only to find content items according to the action discussed, but to enable actions to be taken with the content. As a simple example, you might find an event, and click a button to confirm your attendance. Behind the scenes, that action will be managed by the vocabulary.

The schema actions are diverse. Some describe high-level activities such as to travel, while others refer to very granular activities, such as to follow somebody on a social network. Some task are real world tasks, and others strictly digital ones. I presume real-world actions are included to support activity-reporting from the Internet of Things (IoT) devices that monitor real-world phenomena such as exercise.

screenshot of schema.org actions terms
Schema.org actions taxonomy (partial)

Framenet, a semantic tagging vocabulary used by linguists, is a another general vocabulary that provides coverage of verbs. If a sentence uses the verb “freeze” (in the sense of “to stop”), it is tagged with the concept of “activity_pause.” It is easiest to see how Framenet verb vocabulary works using an example from David Caswell’s project, Structured Stories. Verbs that encapsulate events form the core of each story element. [2]

screenshot structured stories
Screenshot from the Structured Stories project, which uses Framenet.

Applications of Task Taxonomies

While both these vocabularies describe actions at the sentence or statement level, they can be applied to an entire article or section of content as well.

A task focus offers several benefits. Brands can track and manage content about activities independently of who specifically is featured doing the activity, or where/what the object or outcome of the activity is. So if brands produce content discussing options to travel, they might want to examine the performance of travel as a theme, rather than the variants of who travels or where they travel.

Task taxonomies also enable task-focused navigation, which lets people to start with an activity, then narrow down aspects of it. A sequence might start: What do you want to do? Then ask: Where would you like to do that? The sequence can work in reverse as well: people can discover something of interest (a destination) and then want to explore what to do there (a task).

Situational taxonomies

A second option uses nouns to indicate the notable events or situations discussed. Using nouns as proxies for actions unfortunately doesn’t capture a sense of dynamic movement. But if you can’t support a faceted taxonomy that can mix nouns and verbs, it may be the most practical option. When you have a list of descriptors that express actions discussed in your content, you are more likely to tag these qualities than if your taxonomy is entirely thing-centric. I’ll call a taxonomy that represents occasions using noun phrases a situational taxonomy. The terms in a situational taxonomy describe situations and events that may involve one or more activities.

If you have ever done business process modeling, you are familiar with the idea of describing things as passing through a routine lifecycle. We reify activities by giving them statuses: a project activity is under development, in review, launched, and so on. Many dimensions of our work and life involve routines with stages or statuses. When we produce content about these dimensions, we should tag the situation discussed.

One way to develop a situational taxonomy is by creating a blueprint of a detailed user journey that includes an end-to-end analysis of the various stages that real-world users go through, including the “unhappy path” where they encounter a situation they don’t want. Andrew Hinton has made a compelling case in his book Understanding Context that the situations that people find themselves in drive the needs they have. Many user journey maps don’t name the circumstances, they jump immediately into the actions people might do. Try to avoid doing that. Name each distinct situation: both the ones actively chosen by them as well as those foisted on them. Then map these terms to your content.

Situational taxonomies are suited to content about third parties (news for example) or when emphasizing the outcomes of a process rather than the factors that shape it. Processes that are complex or involve chance (financial gyrations or a health misfortune, for example) are suited to situational taxonomies. A situational taxonomy term describes “what happened?” at a high level. Thinking about events as a process or sequence can help to identify terms to describe the action discussed in the content.

The technical word for making nouns out of verbs is “nominalization.” For example, the verb “decide” becomes the noun “decision.” Not all nominalizations are equal: some are very clunky or empty of meaning. Decision is a better word than determination, for example. Try to keep situational terms from becoming too abstract.

Situational taxonomies are less granular than task-based ones. They provide an umbrella term that can represent several related actions. They can enhance tracking, navigation and recommendations, but not as precisely as task-based terms. Task taxonomies express more, suggesting not only what happens, but also how it happens.

Key Verbs Mark the Purpose of the Content

Identifying key verbs can be challenging work. Not all headlines will contain verbs. But ideally the opening paragraph should reveal verbs that frame the purpose of the article. Content strategists know that too much content is created without a well-defined purpose. Taxonomy terms focused on actions indicate what happens in the content, and suggest why that matters. Headlines, and taxonomy terms that rely entirely on nouns, don’t offer that.

We will look at some text from an animal shelter. I have intentionally removed the headline so we can focus on the content, to find the core concepts discussed. A simple part-of-speech app will allow us to isolate different kinds of words. First we will focus on the verbs in the text, which includes the terms “match”, “spot”, “suit”, “ask”, and “arrange”. The verb focus seems to be “matching.” Matching could be a good candidate term in a task taxonomy.

part of search view of verbs in narrative

Now we’ll look at nouns. In additional to common nouns such as dogs and families, we see some nouns that suggest a process. Specifically, several nouns include the word “adoption.” Adoption would be a candidate term in a situational taxonomy. Note the shift in focus: adoption suggests a broader discussion about the process, whereas matching suggests a more specific goal.

part of search view of nouns in narrative

When you look at content through the lens of verbs, questions arise. What verbs capture what the content is describing? Why is the content here? What is the reader or viewer supposed to do with this information? Could they tell someone else what is said here?

If you are having trouble finding key verbs, that could indicate problems with the content. Your content may not describe an activity. There is plenty of content that is “background content,” where readers are not expected to take any action after reading the content. If your goal for producing the content is simply to offer information for reference purposes, then it is unlikely you will find key verbs, because the content will probably be very noun-centric. The other possibility is that the writing is not organized clearly, and so key actions discussed are not readily seen. Both possibilities suggest a strategy check-up might be useful.

Avoid a Hollow Taxonomy

Even when tagging well-written content, capturing what activity is represented will require some effort. This can’t be automated, and the people doing the tagging need to pay close attention to what is implied in the content. They are identifying concepts, not simply matching words.

Tagging is easier to do when one already has vocabulary to describe the activities mentioned in your content. That requires auditing, discovery and planning. If your taxonomy only addresses things and not actions, it may be hollow. It can have gaps.

Most content is created to deliver an outcome. Metadata shouldn’t only describe the things that are mentioned. It should describe the actions that the content discusses, which will be explicitly or implicitly related to the actions you would like your customers to take. You want to articulate within metadata the intent of the content, and thus be in a position to use the content more effectively as a result. Key verbs let you capture the essence of your content.

By identifying key verbs, brands can use active terminology in their metadata to deliver content that is aligned with the intent of audiences.

diagram of key verb roles
How key verb metadata can support content outcomes

The Future Web of Verbs

Web search is moving “from the noun to the verb,” according to Prabhakar Raghavan, Google’s Vice President of Engineering.

We are at the start of a movement toward a web of verbs, the fusing of content and actions. Taxonomy is moving away from its bookish origins as the practice of describing documents. Its future will increasingly be focused on supporting user actions, not just finding content. But before we can reach that stage, we need to understand the relationship between the content and actions of interest to the user.

Taxonomies need to reflect the intent of the user. We can understand that intent better when we can track content according to the actions it discusses. We can serve that intent better when we can offer options (recommendations or choices) centered on the actions of greatest interest to the user.

The first area that verb taxonomies will be implemented will likely be transactional ones, such as making reservations using Schema actions. But the applications are much broader than these “bottom of the funnel” interventions. Brands should start to think about using action-oriented taxonomy terms through their content offerings. This is an uncharted area, linking our metadata to our desired content outcomes.

— Michael Andrews


  1. Key verbs build on the pre-semantic idea of key words, but are specific to activities, and represent concepts (semantic meaning) instead of literal word strings.  ↩
  2. You can watch a great video of the process on YouTube.  ↩
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Intelligent Content

Ontology for the Perplexed

Sooner or later people who deal with content hear about an odd word called ontology.  It is often discussed as a forbidding topic: the representation of all knowledge, and the source of endless grief for those who dare to wrestle with it.  I’ve seen online debates of people trying to define what it is, often by comparing it to other forms of content organization.  These definitions are sometimes theoretical, sometimes impossibly mechanical, and routinely confusing.

Ontology is often shrouded in mystery.  But it is an important topic with practical uses.  Ontologies are used to organize content on various topics, though the details of specific implementations can be complex.  In an effort to distill some of the essence of what ontology is about, I read a recent book by an analytic philosopher named Nikk Effingham entitled An Introduction to Ontology (Polity Press, 2013).  I learned that ontology is a controversial field, full of debates and disagreements about terminology.  While the details of the philosophy were less practical than I might have hoped, I did find the range of topics debated useful to understanding many foundational issues content strategy professionals must take into consideration.

To get a sense of the importance of ontology, consider the emerging field of the Internet of Things.  Already, we have a multitude of things that are connected together, each sending out signals indicating what each thing is sensing. The devices and the systems they interact with, are constantly sensing, monitoring, and interpreting.  These signals may address social, physical, biological, or cognitive phenomenon.  What do all these signals mean?  Deciphering and translating their meaning is partly the role of ontology.

There are plenty of complex definitions of ontology, but I will offer a more direct one.  Ontology is simply identifying and describing what exists that might be significant.  We can refer to what exists generically as a thing.  We need to define what is the thing is, especially since we commonly define things in terms of other things.

When I looked at some of the philosophy that inspired this way of thinking, I found several themes that resonated with me that seemed of practical value.  I will summarize these below in several propositions.  They are my insights, rather than a summary of the field, which as I noted, it far from consensus.

Before we try to construct an elaborate network of inter-related definitions, the formal mechanics of ontology, it is important to identify dimensions that can impact how we define things.

image via synsemia
image via synsemia

Use Properties To Help You Establish How Similar Things Are

We can identify various properties associated with a thing.  The more properties a thing shares with another thing, the more likely the two things are related, all things equal.  Related things will be seen as complementary or competitive with each other.

The properties should be meaningful and hold significance.  Trivial properties (for example, something true in all cases) won’t convey much useful information.  The property that is most unique about a thing is often interesting, although it is also possible the property is not significant.  A test of significance is looking at the potential explanatory value of a property.  Might the property influence the behavior of the thing, or perhaps other things that interact with it?   Suppose we divide things into those that have metallic finish colors, and those with matte finish colors.  Is that difference significant, or inconsequential?  The significance of properties will depend on the context.  Rarely does one property alone entirely sway outcomes, so the covariation of properties are most interesting.

Differentiate Whether Things are Equivalent, or the Same

Sometimes a single thing is described in different ways.  Sometimes different things are described in the same way.

We know a single individual can have different monikers.  Mark Twain was the same person as Samuel Clemens, but unless we are aware that this author used a pen name, we might believe the names referred to different people.

A more challenging issue is when we want to see things that are broadly similar as being a single item.  We can match up things that agree on numerous properties and will say they are the same kind of thing.  When every property is identical, we can be tempted to assume the two things themselves are identical.  But we can be tricked into seeing things as identical when they are merely equivalent, due to the limitations of our descriptions.  Suppose all Model Z computers share the same properties we have identified — they have the same specs.  There is a bug in the computer, and the engineering team develops a fix.  The customer service team announces that Model Z’s problems are now fixed.  But a group of people using the Model Z continues to experience problems.  It turns out their computers are not exactly identical to other users: perhaps they have loaded software from Adobe or Oracle, which is outside of the specs the manufacturer tracks, which created the conflict.

Any time there are two or more instances of a thing, there will be some variation.  Sometimes that variation is so minor we can comfortably say the instances are effectively identical.  It is useful to know how much variation might be possible before assuming all instances of a thing will behave the same way.  And it is very important not to treat clusters of things (including people) that seem broadly similar as being identical.  There’s much value knowing how things might be equivalent to one another, but one should also be aware of potential differences.

Distinguish Categorical and Qualified Descriptions

Many descriptions are factual, and not subject to interpretation or subsequent change.  Your car will generally have the same engine size over its lifespan.  We say your car is a V-6: it is part of the identity of the car.  For many tangible things, as long as the thing exists, its properties will remain the same, even when it reaches the landfill.

Some descriptions are qualified by time or place.  When we see a map on a sign saying “you are here” we know that  “here” is relative to our current location and changes as we move around.  If we were to view this sign through a webcam remotely, the message would be incongruous.  As mobile technology allows us to shift location and time zones and communicate asynchronously, descriptions of where and when become more challenging.

Time and place can have more subtle effects on identity.  I once worked with a telecommunications firm that had a “family” package.  The marketing staff liked how friendly the word family sounded.  But when defining family, the definition subtly shifted to becoming members of your household.  Then the question arose of who qualifies as a member of a household.  Would children in university count?  If so, would it be only when they are living at home, or when they are away at university?  It may have seemed like an arcane issue to debate that distracted from other tasks, but the issue had significant impacts on sales, recurring revenues, and cost of service.

Ontologists refer to qualified descriptions as indices.  With the rise of big data, we are finding more indices pretending to be solid things.  I shop online, and am told that based on my “profile” I presented with various recommended products.  If I regularly shop for a wide variety of products, my profile is always changing, but never seems to match me, because now I’m seeking something different.

Know Whether a Concept is Abstract or Transitional

We often use intangible concepts to describe things — it helps us make sense of the qualities of a thing.  The meaning of many concepts we use to describe things are stable and familiar, so much so we think of them as real things, rather than as concepts.  When we say something is a meter long, the meaning of a meter is won’t fluctuate — the definition of a meter has been fixed for a couple of centuries.  Such concepts are abstract: independent of time or location.   But some concepts are less fixed, and more subject to time and place.  We might describe a work of art as contemporary, because it was created less than 20 years ago.  But in another five years, it might be more appropriate to call the same unchanged item of art as being modern, especially if the artist were to die.

Cultural values are especially susceptible to changes in meaning over time — just look at how old advertisements describe products in ways we find offensive or clueless today.  A simple example would be the shifting meaning of the term “healthy.”  Occasionally cultural changes can happen even faster than products change, such as gender role changes: for example, eyeliner for men being dubbed guyliner. Even many technology descriptions are conceptual, and transitional.  The label smartphone is just a concept that has no stable identity.  What we consider to be a smartphone has changed over time, and there is no guarantee we will continue using this term in the future.

Concepts are useful.  Just be aware that because they are often not precisely defined, their meaning is more likely to drift over time.

Watch Out for Frankenobjects

People in the marketing world are sometimes prone to package together unrelated items.  Consider Amazon Prime.  What is it, exactly?  Is it a club membership?  A prepaid shipping fee?  A streaming video service?  A music service?  What will it be next year?

Philosophers studying ontology call things that are glued together from parts that are not conceptually related or normally connected as “gerrymandered objects.”  Like gerrymandering in politics, the motivation is to trap something in an incomprehensible identity that changes form over time.  If you have to present a gerrymandered object to audiences, be prepared to do a lot of explaining what it is, how it works, and why it matters.

Understand What a Grouping has in Common

There are two types of groupings: collections and sets.

Collections are groupings of things that have common properties.  They are things that seem to belong together.  We see a collection of clothing for spring that are colored yellow.  The types of clothes are different, but they are all yellow, and all for spring, so they seem like a meaningful collection.  The creation of collections relies on rules based on the properties of things included in the collection.

Sets are things that are placed together on the basis of a choice that may be extrinsic to the properties of the items.  A good example is an online shopping cart. I may have a roll of cellophane tape, a pair of socks, and a bottle of allergy medicine in my cart.  It is a set of things that are unrelated, except for the fact I placed them there at a specific time with the intent to purchase them.  Sets are often created or changed as a consequence of an event.  There may not be any rules about what can be included in a set.

Sets may include related things, but do not have to.  Sets require interpretation to know what they contain, since we may not know the details or themes of their contents except through inspection.  We can combine sets, or look for unique items among several sets.  Whereas common properties define collections, with sets, you might check common or unique properties after making changes to the set.

Both collections and sets are useful, but they serve different purposes.

Understand the Changes of State that are Possible for a Thing

It can be difficult to say when something changes from one state to another.  This is especially true if we can’t identify a specific event responsible for causing the change.  I don’t know when my hair turned from brown to grey.  In fact, when listening to other people’s opinions on this topic, there seems to be minor disagreement.  Not only is change sometimes hard to pin down, it can be subjective as well.  When will my hair stop being grey?  When I shave my head, or dye my hair orange.

We assume hair color will change over time, even though it is generally not a significant property of people.  But we often underestimate the changes in the more significant properties of other things.  This poses two issues. One is that the description fails to update itself when the thing has changed. Another is that we are unprepared for unexpected change, and don’t even have vocabulary ready to describe it.  We need to account for edge cases, and intermediate properties that could be significant.

Closing Thoughts

Creating an ontology is challenging work. They typically require a team of people working over the course of years to develop them.  No one is going to create a new ontology for the Internet of Things in a few weeks time.

But ontological thinking is easier to do, and more immediately applicable.  Ontology reminds us that we often bring a point of view that colors how we perceive and categorize things.  Our view may be influenced by a specific time, place or situation in which we are located.  When we are aware of these factors, we can develop a person-independent description of things.

— Michael Andrews