Skip to content

Introduction#

Welcome to the Laces Hub user manual! The Laces Hub is a platform to publish, share and access Linked Data. This Linked Data is organized into groups and repositories, which can be management through the application's user interface, but also accessed through a REST API in order to apply this data within any applications.

Linked Data#

The term Linked Data refers to a set of best practices for publishing structured data on the Web. These principles have been coined by Tim Berners-Lee in 2006. The principles are:

  • Use URIs as names for things
  • Use HTTP URIs so that people can look up those names
  • When someone looks up a URI, provide useful information
  • Include links to other URIs, so that they can discover more things

More information on Linked Data can be found here.

RDF#

Most data published to Laces Hub will be stored as RDF.

The following definition is taken from the RDF 1.1 Primer.

The Resource Description Framework (RDF) is a framework for expressing information about resources. Resources can be anything, including documents, people, physical objects, and abstract concepts.

RDF is intended for situations in which information on the Web needs to be processed by applications, rather than being only displayed to people. RDF provides a common framework for expressing this information so it can be exchanged between applications without loss of meaning. Since it is a common framework, application designers can leverage the availability of common RDF parsers and processing tools. The ability to exchange information between different applications means that the information may be made available to applications other than those for which it was originally created.

More information can be found under RDF.

non-RDF#

Although RDF is ideal for expressing information, data also comes in other, non-RDF, formats which are better suited to process these types of files. Images and (text) documents are more useful if their are stored in their native format, like JPEG, PNG, TXT or PDF.

Laces Hub allows these types of files to be published and accessed in a same way as RDF data.

Organisation#

All data published within Laces Hub, is organised into a hierarchical structure, consisting of groups, repositories and publications.

Groups#

Groups form the main structure for all content on the platform. Groups allow you to add structure to your repositories and manage access for other users on a high level.

Apart from repositories, groups can also contain nested groups, or subgroups, to further organise your data.

Repositories#

Repositories are the containers for related publications. They often will be dedicated to a single project or purpose.

Publications#

Publications are collections of RDF data. All data found in one publication, together represent a single coherent data set.

Files#

Non-RDF data is stored as files. Files can be referred to from within publications, which is a feature of the Laces Library Manager.

Location#

Laces Hub uses the hierarchical structure mentioned above to organise its publications. This organisation is reflected in the address, or URL, given to each group, repository and/or publications.

Each URL conforms to the following pattern:

http://hub.laces.tech/<group>/<repository>/<publication>

The <group> segment in the URL above, consists of the top-level group and any subgroups within this top-level group. So if the top-level group "semmtech", contains a subgroup "schemas", any repositories inside this subgroup "schemas" will have a URL which starts with:

http://hub.laces.tech/semmtech/schemas/<repository>/<publication>

The <publication> segment can also be created with multiple segments, either for naming purposes or to indicate the version. So if we a <repository> called "laces", which has a "specifications" publication with version "202107021100", then the URL becomes:

http://hub.laces.tech/semmtech/schemas/laces/specifications/versions/202107021100

To summarize these are the values for the placeholders introduced above:

<group>       = semmtech/schemas
<repository>  = laces
<publication> = specifications/versions/202107021100

Versioning#

Laces Hub supports different versioning modes:

  • None: no versioning is used, in case you publish to the same location, yor previous publication will be overwritten (default mode).
  • Incremental: auto-incremental numbering for each subsequent version, e.g. 1, 2, 3, etc.
  • Datetime: uses the current date and time as the version identifier, i.e. 202010231305 (October 23, 2020 at 13:05)
  • Timestamp: a numerical value for the current time, based on the Unix Epoch, i.e. 1603458300000 (also October 23, 2020 at 13:05)
  • Custom: free text label to identify a version, e.g. red, blue, vanilla, etc.

The mode should be defined upon publishing, and cannot be changed for a publication once set.

Access#

In order to access Laces Hub and its content, a user account is required. Once an account has been created, users can either explore the Hub using a web browser or connect 3rd party applications using the Hub's programmatic API. For more information on getting access, please check out Getting started.

REST API#

The Hub exposes web services to manage the concept described above. For more info, see API Basics to get started.