Fig. 4.2.1 A standard data base structure.

In order to load the data into the DBMS, there needs to be a careful definition of the
logical and the physical characteristics of the system. All data—attributes, keys, indexes,
etc.—need to be defined before the data can be loaded into the system.

The notion of structure meaning “able to be managed under a standard DBMS” is a very
widely used understanding of what is meant by structured. The meaning has been around
for a long time and is widely understood by a large body of people.

Data in Big Data

Now, consider what data looks like when it is stored in big data. There is none of the
definitional infrastructure that is found in a standard DBMS. All sorts of data are stored
in big data, and they are stored with no notion of what the structure of the data looks like.

Fig. 4.2.2 shows data stored in big data.

Fig. 4.2.2 Big data.

If the definition of structured is taken to mean “managed by a standard DBMS,” then the
data stored in big data is definitely unstructured.

However, there are different interpretations of what is meant by the term “structured.”
Consider the (very normal) circumstance of big data consisting of many repetitive
records. Fig. 4.2.3 shows that big data can certainly contain blocks of data that are made
up of many repetitive records. There are many instances where big data contains just this
sort of information. Some of the many instances include the following:

Chapter 4.2: What Is Big Data?