(adapted/excerpted from the Open Data Handbook)

Open data is data that can be freely used, reused and redistributed by anyone - subject only, at most, to the requirement to attribute and share-alike. Some requirements for data to be truly open are as follows.

• Availability and access: the data must be available as a whole and at no more than a reasonable reproduction cost, preferably by downloading over the internet. The data must also be available in a convenient and modifiable form
• Reuse and redistribution: the data must be provided under terms that permit reuse and redistribution including the intermixing with other datasets.
• Universal participation: everyone must be able to use, reuse and redistribute - there should be no discrimination against fields of endeavour or against persons or groups. For example, ‘non-commercial’ restrictions that would prevent ‘commercial’ use, or restrictions of use for certain purposes (e.g. only in education), are not fully open.

Why is it so important to be clear about the definition of “open”? The answer: interoperability, which is the ability of diverse systems and organizations to work together (inter-operate). Interoperability allows for different components to work together. This ability to make components and to plug them together is essential to building large, complex systems. Without interoperability this becomes nearly impossible.

The core of a “commons” of data (or code) is that one piece of “open” material can be freely intermixed with other “open” material. This interoperability is key to achieving the main practical benefits of “openness”: the enhanced ability to combine different datasets together and thereby to develop more and better products and services. This ability to combine separate pieces from different sources into larger, more sophisticated systems is the real value of the openness standard.

All data linked to this Open Data portal is published “as is”. The Information is licensed 'as is' and the Information Provider and/or Licensor excludes all representations, warranties, obligations and liabilities in relation to the Information to the maximum extent permitted by law. The Information Provider and/or Licensor are not liable for any errors or omissions in the Information and shall not be liable for any loss, injury or damage of any kind caused by its use. The Information Provider does not guarantee the continued supply of the Information.

(from the Open Knowledge Foundation)

Some common reasons for supporting open data:

• Transparency: In a well-functioning, democratic society citizens need to know what their government is doing. To do that, they must be able freely to access government data and information and to share that information with other citizens. Transparency isn’t just about access, it is also about sharing and reuse — often, to understand material it needs to be analyzed and visualized and this requires that the material be open so that it can be freely used and reused.
• Releasing social and commercial value: In a digital age, data is a key resource for social and commercial activities. Everything from finding your local post office to building a search engine requires access to data, much of which is created or held by government. By opening up data, government can help drive the creation of innovative business and services that deliver social and commercial value.
• Participation and engagement – participatory governance or for business and organizations engaging with your users and audience: Much of the time citizens are only able to engage with their own governance sporadically — maybe just at an election every 4 or 5 years. By opening up data, citizens are enabled to be much more directly informed and involved in decision-making. This is more than transparency: it’s about making a full “read/write” society, not just about knowing what is happening in the process of governance but being able to contribute to it.

When exploring the SmartDublin data catalog, you will find data provided in a variety of formats. The formats were chosen to best match the information the data describes: spreadsheets as CSVs, and geospatial information as GeoJSON or KML, and data provided through APIs (application programming interface). These are all considered open formats and can be used freely in many applications and on most computer operating systems. There is a star rating that indicates the Openness of the data see 5-star Open Data:

To be clear, it is preferable to publish your data with as many stars as possible, eg. as CSV rather than Excel.

The information below will help you better understand the file formats used in the SmartDublin catalog and how you can begin investigating their contents.

• What is it: A tabular (spreadsheet) data format, where the column values are separated by commas. CSV files are both human and machine readable. You may see other “delimiters” used, including tabs.
• Used by: Many applications, including Microsoft Excel, OpenOffice, and Google Docs and by text editors like Sublime Text, TextWrangler, Apple TextEdit, and Microsoft Notepad. When the CSV includes geographic coordinates, you may also open them in desktop mapping applications, such as QGIS, and with web-mapping tools, like GeoJSON.io and CartoDB.

• What is it: JSON is an easily human and machine readable open standard format, which transmits data objects consisting of attribute-value pairs. GeoJSON is an extension of JSON that allows for the encoding of simple geographical features (points, lines and polygons) along with non-spatial attributes. TopoJSON itself extends GeoJSON by “stitching” together shared geometries (e.g. borders). This reduces file size and also facilitates certain visualizations.
• Used by: GeoJSON files can be opened by desktop mapping applications and web-mapping tools, by R (with the right extensions), and by text editors. The online utility ogr2ogr supports conversion from many geospatial file formats into GeoJSON.

• What is it: KML is an XML notation format used to express geographic information (longitude, latitude, altitude) on two- and three-dimensional maps. These files are easily readable by humans and machines.
• Used by: These files were originally developed for use with Google Earth. They can also be opened in a variety of other desktop GIS applications and web-mapping platforms.

• What is it: Shapefiles are one of the most common geospatial formats out there. Like GeoJSON, shapefiles can store both spatial geometries (points, lines and polygons) and other feature attributes. In our data catalog, you will find shapefiles zipped together with a few other files (with extension .shx, .dbf, .sbn).
• Used by: In addition to ArcGIS, these files can be opened in free an open source GIS applications like QGIS. They can also be converted to many other data formats.

• What is it: A widespread document format developed by Adobe for sharing text and images in a fixed, un-layered layout. Text from PDFs created with optical-character recognition technology can be copied and pasted to a more open format.
• Used by: Most modern web browsers (e.g. Firefox, Google Chrome, Opera, Safari), can open PDF files without additional plugins. There are several free applications for viewing (but not necessarily editing) PDFs, including Adobe Reader, Apple Preview, and OpenOffice.

• What is it: A Zip file is a compressed archive file that is used to make large files and collections of files more manageable to the user. When a .zip file is created, data is compressed to reduce the file size. Multiple files can be combined into a single Zip folder, making it easier to upload, download or email a volume of files.
• Used by: If you are using Windows 10 or Mac, they support zip natively. Alternatives include 7-Zip (Windows); there are many third-party apps for Mac.