Gerda and Walter Koch of AIT Applied Information Technology Graz, Austria write:
LoCloud provides support services and tools to regional and local heritage institutions. These tools and services simplify ingestion of data into Europeana and help to improve metadata quality with the use of cloud-based services. One of the LoCloud services developed during the second project year is the vocabulary microservice.
Microservices? An introduction
The past years have seen a move from monolithic applications towards microservice architectures. Microservice architectures are generally described as suites of small and independent services compiled into single applications, in opposite to monolithic applications that are built as single units, with a client-side user interface, a database, and a server-side application. While any changes to monolithic applications require the re-building and deployment of the entire applications, in microservice architectures it is quite easy to introduce new versions of the individual services or integrate new services. This will become even more important in the future, as applications will increasingly be deployed to the cloud.
Figure 1 – Monolithic versus microservices architecture
Microservices are independently deployable and scalable and they could even be written in different programming languages by different software teams. Usually. the services are built upon business capabilities and communicate via web service requests or remote procedure calls.
The LoCloud microservices have been developed by different project partner teams and are being deployed in the LoCloud MORe  aggregator. Additionally, some of the services provide front-end applications. The LoCloud vocabulary microservice provides the business capability for vocabulary management and enrichment of metadata.
Vocabulary services support the enrichment of metadata (catalogue data) by adding vocabulary terms to metadata records. This can be done right “at the beginning” when the object is registered in the local cataloguing system. Alternatively, the data can be enriched by an automated service “after” cataloguing has taken place. The second possibility often prevails when data is ingested into joint virtual catalogues (like Europeana) where common vocabularies provide a means to semantically link data and to support easy browsing through the entire repository.
The LoCloud microservice “Generic enrichment” automatically receives the vocabularies available in the vocabulary tool and uses them during the automated enrichment process conducted in the MORe aggregator.
To date around 30 vocabularies are imported to the vocabulary tool. A list of these vocabularies can be found here > LoCloud Vocabularies.
Figures 2 and 3 show how the microservices Vocabulary and Vocabulary Matching (available currently for English and Spanish language) are added to a data source enrichment plan in the the MORe aggregator.
Consequently, the EDM metadata is checked against the LoCloud vocabularies and where appropriate the vocabulary links are added.
Use Case 2 – Match vocabulary terms in the aggregator.
Instead of matching the vocabularies automatically to the metadata it is possible to selected individual terms from the LoCloud vocabularies that should be added to the metadata. These selections are called Subject Collections in MORe.
Use case 3 – Use the vocabularies in your local cataloguing systems via web services
One of the benefits of microservices is that these small and independent services may be plugged in into other application and can be used via the APIs  they provide. Figure 6 depicts an example of a local cataloguing system for music archiving that calls the vocabulary web service in the metadata field “Genre(s)”. The technical information on how the services can be integrated is published on the LoCloud online support centre. There are currently fifteen different web service calls for vocabulary integration available.
Use case 4 – The vocabulary experimental application.
The LoCloud vocabularies have been imported into the Tematres tool in order to use them via web services in the aggregation process. But
Tematres can also be used to create vocabularies from the scratch or to import already existing vocabularies. The advantage of importing vocabularies to the tool is clear: The vocabularies become available in SKOS format with an own web presence and can be used for semantic linking afterwards. With the consent of the vocabulary owner, the vocabulary might then become available for other LoCloud partners in the MORe aggregator. Moreover, the LoCloud Tematres installation allows collaborating online in creating and extending vocabularies (for example in order to create new translations of existing vocabularies).
The vocabulary application is accessible through this link (see figure 7). Please check the LoCloud support portal for information on a test user account which is necessary to access and create a new vocabulary.
http://en.wikipedia.org/wiki/Application_programming_interface 26 January, 2015