What is metadata and why is it as important as the data itself?

Features Data tips

August 25, 2016

Reading time: 8 min

Metadata. You may have heard the term before, and may have asked yourself either "what is metadata?" or "why is it as important as data?" This article will be an attempt to provide answers to these two questions.

Metadata can be explained in a few ways:

Learn more about Metadata in this article: All you need to know about Metadata.

In short, metadata is important. I like to answer this "what is metadata" question as such: metadata is a shorthand representation of the data to which they refer. If we use analogies, we can think of metadata as references to data. Think about the last time you searched Google. That search started with the metadata you had in your mind about something you wanted to find. You may have begun with a word, phrase, meme, place name, slang or something else. The possibilities for describing things seems endless. Certainly metadata schema can be simple or complex, but they all have some things in common.

Metadata Have Been Around for a While

What is metadata - an analogy to help understand. 
Hanford's historic (1943) B Reactor is part of the Manhattan Project Historical National Park. Courtesy TRIDEC.


Old-Timey Provenance: Proto-Metadata

I am not that old, but I am old enough to remember doing my job without digital aids. In the early 90s, I was a (then) young archaeologist working for Battelle Pacific Northwest Laboratory on the Hanford Project. Hanford is the US extraction facility for weapons grade plutonium. It was also where the United States processed enriched Uranium for the bombs dropped on Nagasaki and Hiroshima in 1945. Enrico Fermi had a lab there and the US Department of Energy saw this facility as having historical significance. There is a point to this anecdote. In 1992 and 1993, we had basic tcp/ip, but we did not have the array of digital tools we have today.

Provenance was the word used back then to describe the origins and the nature of objects. If I unearth an artifact and I take it out of its context, that is, I remove it from the site, what would happen to its scientific value? That depends on how well I describe that provenance and if I use the right keywords and organizational principles that are used to categorize, describe, analyze and curate similar objects and artifacts. This is why looting of archaeological sites is so damaging. Not only is the object lost but even if recovered it has lost its provenance or meaning!

This anecdote hopefully starts to form an idea that data on the data is as important as the data itself. Without having context, data has little reuse value.

Metadata is as Valuable as the Data

Archaeologists can help us answer the question "what is metadata" through their work.
Archaeologist is bagging an artifact and recording metadata on the bag to keep the artifacts' scientific value intact. Photo by Cliff Mine

Using the context of my job as an archaeologist, an object loses its scientific value if it loses its provenance or metadata. Every artifact is bagged and tagged using a numerical reference on the bag that corresponds to notes in a log. Often there are photos and sketches made of the artifact in-situ (in its original state) for future research. Archaeology is not about treasure hunting. open data is not just about storytelling. Both endeavors are fun and exciting. But the useful side of both open data and Archaeology is about the amount of reuse we can derive from our objects whether they be stones and bones or massive datasets.

Defining Metadata Using Multiple Sources

Now that we have a more basic answer to our original question "what is metadata", let's take a look at what others have had to say. I use two definitions as a reference: one from the International Standards Organization (ISO), the other from White House Roundtables that I attended (both on Data Quality and on open data for Public-Private Collaboration), as we co-constructed a definition in the presence of experts.

The ISO and the White House Roundtables definition on data quality have some subtle differences. First, provenance in the White House context is defined as the metadata of a dataset. The second difference is that there is no "timeliness" dimension to the ISO definition of Data Quality. The ISO predates the widespread adoption of open data. Perhaps timeliness will become a part of the ISO in the future. The ISO provides a semantic definition to Data Quality which serves as the metadata requirement. To make this easier to discuss, we will conflate the definitions of provenance and semantics into a third term called metadata.

What is metadata: Creating our own Definition

According to Liu and Ram's "A semiotic Framework for Analyzing Data Provenance Research", the word provenance used in the context of data has different meanings for different people. Liu and Ram go on to define the semantic model of provenance in this and several other works as a seven piece conceptual model.

Liu and Ram conceptualize data provenance as consisting of seven interconnected elements including what, when, where, who, how, which, and why. These are elements of several metadata frameworks. Basically, most metadata schemas ask these elements about their data.

The W7 Ontological Model of Metadata

So, if we conflate these two terms into metadata, we are saying that metadata gives the following information about the data it models or represents:

  • What
  • When
  • Where
  • Who
  • How
  • Which
  • Why

Opendatasoft natively uses a subset of DCAT to describe datasets. The following metadata is available:

  • title,
  • description,
  • language,
  • theme,
  • keyword,
  • license,
  • publisher,
  • references.
It is possible to activate the full DCAT template, thus adding the following additional metadata: created, issued, creator, contributor, accrual, periodicity, spatial, temporal, granularity, data quality.


A full INSPIRE template is also available and can be activated on demand. The creation of a fully custom metadata template can also be done.

How to Use Metadata to enhance data reuse

A lot of the discussions around data quality and data discoverability have revolved around metadata and something called ontologies. Ontologies are descriptions and definitions of relationships. Ontologies can include some or all of the following descriptions/information:

  • Classes (general things, types of things)
  • Instances (individual things)
  • Relationships among things
  • Properties of things
  • Functions, processes, constraints, and rules relating to things.

Ontologies help us to understand the relationship between things. As an example, an "android phone" is a subject of an object class, "cell phone".

Some refer to an "ontology spectrum" that describes some frameworks as weak and others as strong. This "spectrum" encapsulates the range of opinions as to what an ontology really is.

Using Ontologies to Enhance Discoverability in Metadata

Imagine we have a dataset about building permits. We may want to compare the nature of our dataset of permits with another dataset of permits. Fortunately for us, there is a standard emerging for permit data called BILDS. From the BILDS website, we see a specification and 9 municipalities all using the BILDS specification. From the BILDS GitHub account we can see a set of required standards for a permit dataset. (See Core Permits Requirements)

If our dataset matched the schemas of those 9 municipalities, then we can say they would interoperate. We still need to add some discoverable metadata around them. This is easier because all of these datasets share a similar schema. Our metadata could provide a standard definition for each column header type. This means all 9 datasets would have an increase in discoverability as well. We know what to look for.

Our Data Enriched with Valuable Metadata

At the beginning of this article, we talked about open data and Data Quality. We also made the assertion that metadata were as valuable as the data itself. We then explored some of the anatomy and definitions of metadata, ontologies, schemas, and standards.

Data quality is connected to the provenance of that data. Without metadata to provide provenance, we have a dataset without context. Data without context, like an artifact, chemical, baking soda, or any other random object, has little value. What I learned from the two White House Roundtables reinforced this concept for me. Recently I finished an open data project for a municipality and I was harvesting GIS data. Most of these data had no metadata, which made it frustrating for me to use it. Metadata alone can be extremely useful. Metadata can provide pointers to datasets, even without the actual data. We can put together an organizational chart around data that exists for a given topic.

Other Discussions on Defining Metadata

  • Dugas, M., et al. "Memorandum 'Open Metadata'." Methods of information in medicine 54.4 (2015): 376-378.

  • Detken, Kai-Olivier, Dirk Scheuermann, and Bastian Hellmann. "Using Extensible Metadata Definitions to Create a Vendor-Independent SIEM System." International Conference in Swarm Intelligence. Springer International Publishing, 2015.

  • Jiang, Guoqian, et al. "Using Semantic Web Technologies for the Generation of Domain-Specific Templates to Support Clinical Study Metadata Standards." Journal of biomedical semantics 7.1 (2016): 1.

  • McCrae, John P., et al. "One Ontology to Bind Them All: The META-SHARE OWL ontology for the Interoperability of Linguistic Datasets on the Web." European Semantic Web Conference. Springer International Publishing, 2015.

  • Riechert, Mathias, et al. "Developing Definitions of Research Information Metadata as a Wicked Problem? Characterisation and Solution by Argumentation Visualisation." Program 50.3 (2016).

  • S. Ram and J. Liu, "A Semiotics Framework for Analyzing Data Provenance Research," Journal of Computing Science and Engineering, vol. 2, pp. 221-248, 2008.)

  • Wilson, Samuel P. Developing a metadata repository for distributed file annotation and sharing. Diss. PURDUE UNIVERSITY, 2015.

Other Discussions on Ontologies and Ontology

  • Polleres, Axel and Simon Steyskal. "Semantic Web Standards for Publishing and Integrating open data." Standards and Standardization: Concepts, Methodologies, Tools, and Applications (2015): 1.

  • Daraio, Cinzia, et al. "The advantages of an Ontology-Based Data Management Approach: Openness, Interoperability, and Data Quality." Scientometrics (2016): 1-15.

  • Fukuta, Naoki. "Toward an Agent-Based Framework for Better Access to open data by Using Ontology Mappings and their Underlying Semantics." Advanced Applied Informatics (IIAI-AAI)2015 IIAI 4th International Congress. IEEE, 2015.

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  • We created this guide to help you improve the quality of your metadata and thereby ensure your data gets reused. Inside, you will find:
    20 essential metadata attributes recommended by international standards.
    7 golden rules for describing your metadata.
    A table summarizing the metadata attributes.
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