Whether you’re building a thin client (web application) or a thick client (client-server application), at some point you’ll probably be making requests to a web server and need good data formatting for responses. Currently, three main data formats are used to transmit data from a web server to a client: CSV, XML, and JSON. To develop an application with a solid architecture, it’s a good idea to understand the differences between each format and know when to use them. The purpose of this post is to define each data format, discuss the advantages and disadvantages of each, and discover which situations work best with each format.

CSV

CSV stands for “comma separated values”. As the name implies, this data format is basically a list of elements separated by commas. Let’s say your response is sending a list of people from a particular family. The format would look like this:

Eric, Andrea, Kusco

Pros: This format is the most compact of the three formats. Generally speaking, CSV formats are about half the size of XML and JSON formats. This is the main advantage of CSV because it can help reduce bandwidth

Cons: This format is the least versatile of the three formats. This is because a homebrew parser is required to convert the CSV data to a native data structure. As a result, if the data structure changes, there is an associated overhead of having to change or even redesign your parsers. Also, since the program that creates the CSV and the program that parses the CSV reside on different machines (remember we are passing data from one machine to another), both programs must be updated simultaneously to prevent the receiving program from crashing. Otherwise, an outage is required to update both programs individually to avoid incompatibility issues.

Finally, CSV doesn’t really support data hierarchies. What if you wanted to submit attributes for each person in each family? You would then have to design a complex parser that knows which parts of the CSV refer to elements of a family and which parts refer to elements of each person. One way to solve this problem is to use another delimiter like “;” to separate the attribute of each person:

Eric;male;26,Andrea;female;26,Kusco;male;8

However, the problem with creating custom formats is that you incur the maintenance overhead of an even more complex parser.

XML

XML stands for “Extensible Markup Language”. XML was designed in 1996 and officially became a W3C standard in 1998. It was created to better represent data formats with a hierarchical structure. The format looks like this:

Pros: This data format fully supports hierarchical data structures and is very appropriate when complex data is received in response. It is also very readable for humans. Most browsers have built-in XML readers that allow you to inspect XML files. Since XML was the first standard hierarchical data format, most APIs have built-in functionality to automatically convert XML data streams to native data structures as objects.

Cons: This data format is about three times larger than CSV. This is because each data item has an associated opening and closing parameter tag.

JSON

JSON stands for (Javascript Object Notation). It was invented in 2001 and was popularized by Yahoo and Google in 2005 and 2006. It was created as an alternative to XML. However, like XML, it represents hierarchical data with the use of commas, braces, and brackets. An example of JSON looks like this:

{“name”:”Eric”,”age”:”26″},

{“name”:”Andrea”,”age”:”26″},

{“name”:”Kusco”,”age”:”8″}

Pros: This data format supports hierarchical data and is smaller than XML. As the name implies, it was also built to more easily parse data into native Javascript objects, making it very useful for web applications. JSON is the best of both worlds compared to CSV and XML. It’s simple and compact like CSV, but supports hierarchical data like XML. Unlike XML, JSON formats are only twice as large as CSV formats.

Cons: This data format has slightly less support than XML. Since JSON is relatively newer than XML, there are fewer APIs to automatically convert JSON to native data structures. However, this is changing rapidly because newer APIs and plugins support XML and JSON.

conclusion

As a general rule, JSON is the best data exchange format to date. It is light, compact and versatile. CSV should only be used if you are sending large amounts of data and bandwidth is an issue. Today, XML should not be used as a data exchange format because it is more suitable for document markup.