QL4MDR: a GraphQL query language for ISO 11179-based metadata repositories

Abstract

BackgroundHeterogeneous healthcare instance data can hardly be integrated without harmonizing its schema-level metadata. Many medical research projects and organizations use metadata repositories to edit, store and reuse data elements. However, existing metadata repositories differ regarding software implementation and have shortcomings when it comes to exchanging metadata. This work aims to define a uniform interface with a technical interlingua between the different MDR implementations in order to enable and facilitate the exchange of metadata, to query over distributed systems and to promote cooperation. To design a unified interface for multiple existing MDRs, a standardized data model must be agreed on. The ISO 11179 is an international standard for the representation of metadata, and since most MDR systems claim to be at least partially compliant, it is suitable for defining an interface thereupon. Therefore, each repository must be able to define which parts can be served and the interface must be able to handle highly linked data. GraphQL is a data access layer and defines query techniques designed to navigate easily through complex data structures.ResultsWe propose QL4MDR, an ISO 11179-3 compatible GraphQL query language. The GraphQL schema for QL4MDR is derived from the ISO 11179 standard and defines objects, fields, queries and mutation types. Entry points within the schema define the path through the graph to enable search functionalities, but also the exchange is promoted by mutation types, which allow creating, updating and deleting of metadata. QL4MDR is the foundation for the uniform interface, which is implemented in a modern web-based interface prototype.ConclusionsWe have introduced a uniform query interface for metadata repositories combining the ISO 11179 standard for metadata repositories and the GraphQL query language. A reference implementation based on the existing Samply.MDR was implemented. The interface facilitates access to metadata, enables better interaction with metadata as well as a basis for connecting existing repositories. We invite other ISO 11179-based metadata repositories to take this approach into account.

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“…Both are metadata standards, with the ISO/TS 21526 explicitly targeting the health care sector [ 53 ]. However, as they do not provide a specific data format to support the syntactic compatibility of information [ 54 ], integration is currently not prioritized.…”

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“…The research began by building an integrated system of competency tests then input the data into the database. This system will be built with 2 concepts in the API, Graph-QL and REST [15], the data will be used as output requests f rom clients, then test and comparing the performance of each API concept that has been built using the characteristics of QoS (Quality of Service). As shown in Figure 1.…”

“…It is also designed to make APIs faster, more f lexible and developer f riendly [3]. As a REST alternative, Graph-QL allows developers to make requests that pull data from multiple data sources in a single APIs endpoint [4]. In addition, the API manager will also have the f lexibility to be able add and remove f ields without having af f ect to existing queries [5].…”

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“…The major difference is that SOA focuses on integration and service orchestration (usually requiring a sophisticated middleware), whereas Microservices focus on separating the business logic into small independent components [CDT18,FML17,Ric15]. SOA and Microservices imply a distributed system architecture, which adds further complexity in terms of communication, synchronization, safety and security [TS07].…”