With the rise of mobile devices claiming a greater and greater portion of internet traffic, optimizing performance of data fetching becomes more important. A common technique of communicating between subsystems of online applications is through web services using the REpresentational State Transfer (REST) architectural style. However, REST is imposing restrictions in flexibility when creating APIs that are potentially introducing suboptimal performance and implementation difficulties. One proposed solution for increasing efficiency in data fetching is through the use of frameworks for declarative data fetching. During 2015 two open source frameworks for declarative data fetching, Falcor and Relay+ GraphQL, were released. Because of their recency, no information of how they impact performance could be found. Using the experimental approach, the frameworks were evaluated in terms of latency, data volume and number of requests using test cases based on a real world news application. The test cases were designed to test single requests, parallel and sequential data flows. Also the filtering abilities of the frameworks were tested. The results showed that Falcor introduced an increase in response time for all test cases and an increased transfer size for all test cases but one, a case where the data was filtered extensively. The results for Relay+GraphQL showed a decrease in response time for parallel and sequential data flows, but an increase for data fetching corresponding to a single REST API access. The results for transfer size were also inconclusive, but the majority showed an increase. Only when extensive data filtering was applied the transfer size could be decreased. Both frameworks could reduce the number of requests to a single request independent of how many requests the corresponding REST API needed. These results led to a conclusion that whenever it is possible, best performance can be achieved by creating custom REST endpoints. However, if this is not feasible or there are other implementation benefits and the alternative is to resort to a "one-size-fits-all" API, Relay+GraphQL can be used to reduce response times for parallel and sequential data flows but not for single request-response interactions. Data transfer size can only be reduced if filtering offered by the frameworks can reduce the response size more than the increased request size introduced by the frameworks. / Alteftersom användningen av mobila enheter ökar och står för en allt större andel av trafiken på internet blir det viktigare att optimera prestandan vid datahämtning. En vanlig teknologi för kommunikation mellan delar internet-applikationer är webbtjänster användande REpresentational State Transfer (REST)-arkitekturen. Dock introducerar REST restriktioner som minskar flexibiliteten i hur API:er bör konstrueras, vilka kan leda till försämrad prestanda och implementations-svårigheter. En möjlig lösning för ökad effektivitet vid data-hämtning är användningen av ramverk som implementerar deklarativ data-hämtning. Under 2015 släpptes två sådana ramverk med öppen källkod, Falcor och Relay+GraphQL. Eftersom de nyligen introducerades kunde ingen information om dess prestanda hittas. Med hjälp av den experimentella metoden utvärderades ramverken beträffande svarstider, datavolym och antalet anrop mellan klient och server. Testerna utformades utifrån en verklig nyhetsapplikation med fokus på att skapa testfall för enstaka anrop och anrop utförda både parallellt och sekventiellt. Även ramverkens förmåga att filtrera svarens data-fält testades. Vid användning av Falcor visade resultaten på en ökad svarstid i alla testfall och en ökad datavolym för alla testfall utom ett. I testfallet som utgjorde undantaget utfördes en mycket omfattande filtrering av datafälten. Resultaten för Relay+GraphQL visade på minskad svarstid vid parallella och sekventiella anrop, medan ökade svarstider observerades för hämtningar som motsvarades av ett enda anrop till REST API:et. Även resultaten gällande datavolym var tvetydiga, men majoriteten visade på en ökning. Endast vid en mer omfattande filtrering av datafälten kunde datavolymen minskas. Antalet anrop kunde med hjälp av båda ramverken minskas till ett enda oavsett hur många som krävdes vid användning av motsvarande REST API. Dessa resultat ledde till slutsatsen att när det är möjligt att skräddarsy REST API:er kommer det att ge den bästa prestandan. När det inte är möjligt eller det finns andra implementations-fördelar och alternativet är att använda ett icke optimerat REST API kan användande av Relay+ GraphQL minska svarstiden för parallella och sekventiella anrop. Däremot leder det i regel inte till någon förbättring för enstaka interaktioner. Den totala datavolymen kan endast minskas om filtreringen tar bort mer data från svaret än vad som introduceras genom den ökade anrops-storleken som användningen av ett frågespråk innebär.

REST and GraphQL are the two dominant Application Programming Interface (API) architectures being used for communication with databases. They differ in a lot of aspects, and as such it is not immediately obvious which architecture is preferable. This thesis aims to shed some light onto this problem by exploring two aspects, developer experience, and performance. The method used to measure the developer experience was a case study, in which participants had to write code that communicates with a REST API and a GraphQL API and then answer questions that describe their experience communicating with both. To test the performance, a case study was done in which 5 different benchmarks were ran comparing the two. The results of the first case study show that GraphQL solutions were perceived to give a more overall picture of what is happening than REST solutions. REST was, however, viewed as easier to complete the tasks with. The results of the second case study show that a server that implements REST architecture has better performance during normal circumstances, but GraphQL shows better performance if data is being requested with specified fields. / REST och GraphQL är de två dominerande applikationsprogrammeringsgränssnitten (API) arkitekturerna som används för att kommunincera med databaser. De skiljer sig i många aspekter och därav är det inte uppenbart vilken arkitektur som föredras. Denna avhandling har som mål att reda ut detta problem genopm att utforska två aspekter, utvecklarupplevelsen och prestandan. Metoderna som användes för att mäta utvecklarupplevelsen var en fallstudie, där deltagarna fick skriva kod som kommunicerar med en REST server och en GraphQL server och sedan besvara frågor som beskriver deras upplevelse med att kommunicera med dessa. För att testa prestandan gjordes en fallstudie där 5 olika benchmarks kördes för att jämföra de två servrarna. Resultatet från våran första fallstudien visar på att GraphQL ansågs ha en bättre helhetbild av vad som händer gentemot REST, men när det kom till själva implementaionen av uppgifterna, ansågs REST vara lättare. Resultaten av den andra fallstudien visar att REST arkitekturen har bättre prestanda under normala omständigheter, men att GraphQL har bättre prestanda när datan efterfrågas med enbart specifika fält.

Master of Science / Department of Computing and Information Sciences / Mitchell L. Neilsen / The mobile world is rapidly changing: Smartphones have gone from portable messaging and email devices to streaming-video machines that surf the Web at blazing speed. Now-a-days a smartphone can provide computing capabilities, wireless communication capabilities, run software and perform other tasks just like any traditional computer. These amazing features of a smartphone and Open Source Android market helped in the development of this project. The purpose of this project is to develop an Android application for controlling various elements of user environment. User Controlled Environment is an Android application for home. The environment consists of smart lights, an Android mobile devices for playing music and a display. The application sends the user’s preferred settings to the environment and the respective settings are applied. The preferences are displayed on the screen. The user will be able to view and adjust a variety of environmental preferences. The preferences include the light’s color, light intensity, and the music. When the user exits the application the environment goes to a default state. The users can set preferences which include moods, seven colors of light, three levels of light intensity and songs that the users can select.

Software systems evolve over the life span to accommodate changes in order to meet technical and business requirements. Evolution of open source software (OSS) is challenging because of involvement from a large number of independent teams and developers who make modifications in the systems according to their own requirements. It is required to evaluate these changes as these are being incorporated into the system against the long term evolvability objectives. This paper presents the analysis of the Hackystat, an OSS framework; against analyzability, changeability, extensibility, testability domain specific quality attributes. The analysis of the processes used during the development of the OSS systems is also discussed. On the basis of the analysis and the early research conducted to evaluate software evolvability, an evolvability analysis method for OSS evolution is presented in this report. Guidelines of the model suggest that the requirements identification and analysis, identification of the system components that are to be affected as a result of the change, identification and prioritization of the potential solutions, evaluation of the potential solutions with respect to evolvability characteristics, use of test driven development and automated build tools are the important steps that should be performed to evaluate system changes. Evolvability analysis model also suggests that the team which is responsible to for system overall architecture (project control group) should also evaluate changes submitted by different teams. A case study to modify a service oriented architecture bases system into software as a service cloud model following the guidelines of evolvability analysis model is also presented.

A mobile application is typically divided into two sides that communicate with each other: the front-end (i.e. what the user can see and interact with on the phone) and the back-end (the hidden ”server” side, which processes requests from the front-end). Ways to improve their production cycle are constantly investigated by corporations such as Applidium, which is a French startup company specialized in mobile applications. For instance, the firm often has to deal with external back-ends that are not properly documented, which makes the development of products intricate. Furthermore, test and documentation files for certain parts of projects are manually written, which is time consuming, and are all largely based on the same information (back-end descriptions). Hence, this information frequently finds itself scattered in different files, sometimes in different versions. Having identified issues that most regularly disrupt the work of the company’s employees, a certain number of goals to solve these are set, such as, notably, centralizing all back-end-related information into one authoritative source, and automatizing the generation of test and documentation files. A tool (in the form of a web application) allowing users to describe back-ends, called Pericles, is then proposed as the outcome of the master thesis, to deal with the described problems and materialize the defined objectives. Finally, a qualitative evaluation is performed through a questionnaire designed to assess how users feel the tool helps them in their work, which constitutes the metric for this project. The evaluation suggests that the implemented tool is relevant with respect to the fixed goals, and allows to infer its propensity to help Applidium’s developers and project managers by making the development and validation of projects easier.

The objective of this thesis was to design and implement a scalable and load efficient back-end system for web game services. This is of interest since web applications may overnight gain a significant increase in user base, because of viral sharing. Therefore designing the web application to service an increasing amount of users can make or break the application, in regard to keep the user base. Because of this, testing how well the system performs during heavy load can be used as a foundation when making a decision of when and where to scale up the application. The system was to be generically accessible through an Application Programming Interface (API) by the different game services. This was done using a RESTful architecture where emphasise was put on building the system scalable and load efficient. This thesis focuses on designing and implementing such a system, and how load testing can be used to evaluate this systems performance for an increasing amount of simultaneous clients using the web application. The results from load testing the implemented system was above the expectations, considering the hardware used when running the tests and hosting the system. The conclusion of this thesis is that by following REST when designing a web service, scalability becomes a natural part of how one would design the system.

Software as a service is an emerging but important aspect of the web. WebServices play a vital role in providing it. Web Services are commonly provided in one of two architectural styles: a "REpresentational State Transfer" (REST), or using the "Simple Object Access Protocol" (SOAP.) Originally most web content was text and small images. But more recent services involve complex data structures including text, images, audio, and video. The task of optimizing data to provide delivery of these structures is a complex one, involving both theoretical and practical aspects. In this thesis work, I have considered two architectures developed in the REST architectural style and tested them on mixes of data types (plain text, image, audio) being retrieved from a file system or database. The payload which carries the actual content of a data transmission process can either be in Extensible Markup Language (XML) or JavaScript Object Notation (JSON). Both of these language notations are widely used. The two architectures used in this thesis work are titled as Scenario 1 and Scenario 2. Scenario 1 proposes two different cases for storing, retrieving and presenting the data via a REST web service. We investigate the question of what is the best way to provide different data types (image, audio) via REST Web Service. Payload size for JSON and XML are compared. Scenario 2 proposes an enhanced and optimized architecture which is derived from the pros of the first two cases in Scenario 1. The proposed architecture is best suited for retrieving and serving non-homogeneous data as a service in a homogenous environment. This thesis is composed of theoretical and practical parts. The theory part contains the design and principles of REST architecture. The practical part has a Web Service provider and consumer model developed in Java. The practical part is developed using the Spring MVC framework and Apache CXF, which provides an implementation using JAX-RS, the Java API for RESTful services. A glossary of acronyms used in this thesis appears in the appendix on page 101.

Abstract The Internet of Things vision proposes a global platform in an unforeseen scale for distributed applications that rely on data provided by interconnected resource-constrained things. In such large-scale systems, centralized control of system operation by a single component through vertical interactions becomes unfeasible. Ideally, decentralized control in the proximity of things enables to take into account the local dynamic resource availability and environmental characteristics that are used to optimize the application execution. To realize decentralization, capabilities for horizontal interactions, that complement the vertical interactions, and for opportunistic participation of things are needed. This thesis explores mobile agent technology to implement distributed Internet of Things applications that benefit from both vertical and horizontal interactions of the application components. First, a resource-oriented reactive mobile agent architecture and a software framework are presented. The framework facilitates RESTful interactions between agents and other system components and provides a REST-based interface to build opportunistic agent-based applications. Two agent platforms are presented that integrate resource-constrained things into the framework as mobile agent hosts. Second, mobile agent based mobile crowdsensing and edge computing applications are evaluated with large-scale simulations and real-world experiments. The results show that energy consumption is decreased in the participating things, in comparison with the existing approaches, by agent-based in-network data processing and control of the thing operation. This thesis makes a valuable contribution by enabling mobile agent operations in a heterogeneous set of resource-constrained things. The presented empirical evidence shows how mobile agent technology increases energy efficiency in distributed application execution. The presented mobile agent architecture and software framework potentially accelerate the utilization of mobile agent technology in the Internet of Things. / Tiivistelmä Esineiden Internet liittää resurssirajoitteiset sulautetut laitteet laajamittaisesti Internet-verkkoon, jossa niiden tuottamaa tietoa hyödynnetään hajautettujen järjestelmien sovelluksissa. Esineiden Internetin järjestelmien odotetaan skaalautuvan niin laajoiksi, ettei keskitetty, vertikaaliseen vuorovaikutukseen perustuva järjestelmähallinta ole enää käyttökelpoinen ratkaisu. Hajautettu hallinta lähellä tietoa tuottavia laitteita tuo etuja, kun paikallisesti sovelluksen suorituksessa otetaan huomioon toimintaympäristön tila ja voidaan reagoida dynaamisesti resurssien saatavuuteen. Hajautus Esineiden Internetin sovellusalustoilla edellyttää menetelmiä sekä laitteiden vertikaaliseen ja horisontaaliseen vuorovaikutukseen, että niiden dynaamisen osallistumisen mahdollistamiseksi sovelluksen suorittamisessa. Tässä työssä tutkittiin mobiiliagentti-teknologiaa hajautettujen sovellusten toteuttamiseen Esineiden Internet-ympäristössä. Työssä esitettiin resurssisuuntautunut arkkitehtuuri reaktiivisille mobiiliagenteille sekä ohjelmistokehys, joita käyttäen voidaan toteuttaa agenttipohjaisia hajautettuja sovelluksia. Ohjelmistokehys perustuu REST-arkkitehtuurimalliin, jonka pohjalta esitettiin yhdenmukainen rajapinta agenttien ja järjestelmäkomponenttien väliseen vuorovaikutukseen. Ohjelmistokehyksen osana toteutettiin kaksi mobiiliagentti-ohjelmistoalustaa resurssirajoitteisille sulautetuille laitteille. Työssä tarkasteltiin mobiiliagentti-pohjaisten Esineiden Internet-sovellusten energiatehokkuutta simuloinneilla sekä tosielämän kokeilla. Tarkastelun kohteeksi valittiin joukkoistettu mobiilihavainnointi sekä reunalaskennan ulottaminen resurssirajoitteisiin laitteisiin. Saadut tulokset osoittavat, että laitteiden energiankulutusta voidaan pienentää verrattuna aiemmin esitettyihin ratkaisuihin hyödyntämällä mobiiliagentteja tiedonkäsittelyyn laitteessa sekä laitteen toiminnan ohjaamiseen. Työssä esitetty resurssisuuntautunut mobiiliagenttiarkkitehtuuri sekä ohjelmistokehys edesauttavat mobiiliagentti-teknologian hyödyntämistä resurssirajoitteisissa sulautetuissa laitteissa. Tosielämän kokeista saadut tulokset osoittavat mobiiliagenttiteknologian hyötyjä hajautettujen sovellusten toteuttamisessa Esineiden Internetiin.

Master’s thesis deals with implementation of a European standard DATEX II. This standard specifies the data format for information transmission in road transport. The road traffic is flowing streams of current information. For the work was selected network of meteorological stations, which will publish the measured data, ie weather conditions of road transport. Measured data will be available to consumers in the format DATEX II. Implementation will be operational in its entirety meteorological station from design to the actual web service that will produce data information for consumers.