A formal framework for comparing linked data fragments

Abstract

The Linked Data Fragment (LDF) framework has been proposed as auniform view to explore the trade-offs of consuming Linked Data when serversprovide (possibly many) different interfaces to access their data. Every such in-terface has its own particular properties regarding performance, bandwidth needs,caching, etc. Several practical challenges arise. For example, before exposing anew type of LDFs in some server, can we formally say something about how thisnew LDF interface compares to other interfaces previously implemented in thesame server? From the client side, given a client with some restricted capabilitiesin terms of time constraints, network connection, or computational power, whichis the best type of LDFs to complete a given task? Today there are only a fewformal theoretical tools to help answer these and other practical questions, andresearchers have embarked in solving them mainly by experimentation.In this paper we propose theLinked Data Fragment Machine(LDFM) which isthe first formalization to model LDF scenarios. LDFMs work as classical Tur-ing Machines with extra features that model the server and client capabilities. Byproving formal results based on LDFMs, we draw a fairly completeexpressive-ness latticethat shows the interplay between several combinations of client andserver capabilities. We also show the usefulness of our model to formally analyzethe fine grain interplay between several metrics such as the number of requestssent to the server, and the bandwidth of communication between client and server.