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Adding Hypermedia as the Engine of Application State to RESTful Web Services

Aufgabenbereich: Ableitung von Service-Spezifikationen

Bearbeiter: noch nicht vergeben


- Motivation:

The REST (Representational State Transfer) architectural style includes the principle of Hypermedia as the Engine of Application State (HATEOAS). Response messages of HATEOAS compliant web services contain all possible valid states the web service can take in a next step. Thus, such web service rep-resent a finite-state automaton. Clients that use the web service, only need to know its initial states. Ideally, the clients do not need to be adapted in case this automaton changes afterwards. Many of today's web services that claim to be RESTful do not consider HATEOAS. Such web services are not fully compliant with REST.

- Task:

The task of the bachelor's the-sis is to support developers in making their RESTful web ser-vices HATEOAS compliant. This is to be achieved by us-ing an existing technique that mines behavioral models (pe-tri nets or BPMN models) from call logs. A web service's states and transitions can be represented by such behav-ioral models. These models can be used to determine all next possible states of a web service. The response messages of non HATEOAS compliant web service shall be automatically expanded by the information about the next valid states. Hence, this approach would help to evolve RESTful web services.

- Literature:

Liskin et al.: Teaching old services new tricks: adding HATEOAS support as an afterthought

Kontakt: Simon Schwichtenberg

Anhang: HATEOAS.pdf

Converting Semantic Data to Standard Data Formats



Modern web sites semantically annotated the data they provide. For instance, ticket broker web sites like or provide information about events and tickets not only in a human-understandable but also in a machine-understandable format. To do so, ontologies like are used, which allow annotating entities commonly found on web pages, e.g., events, persons, recipes. Web sites which semantically annotated their data are ranked higher and the data they provide is shown more prominently by search engines. Aside from search engines, this data can also be useful for other applications, i.e., event data could also be stored in calendars. However, in order to use this information in other applications, it has to be converted to a standard data format. In case of event data, this could be the iCalendar format. The development of such converters is often a tedious and error-prone task. Therefore, a methodology shall be developed to simplify the development of high-quality converters, which take semantic data as input and output the data in a standard data format understood by existing applications.




  • Analyze which types can be converted to standard data formats
  • Specify a format to describe what kind of information needs to be included in semantic data in order for a converter to be applicable
  • Develop a methodology  to ensure the development of high-quality converters. The methodology shall define steps and guidelines in order to develop, test, and deploy such converters, e.g., simplify the specification of test cases and develop a continuous delivery pipeline for converters
  • Apply the methodology to develop exemplary converters
  • For Master’s Theses: Mechanism to compensate missing information by utilizing other data sources, e.g., knowledge bases, crowd


Dennis Wolters

Cross-Device Integration of Windows, MacOS, or iOS Applications


Today, our favorite applications are distributed across multiple devices, e.g., we write documents using office applications on desktop computers, share texts and images using messenger on smartphones, or listen to music using our favorite streaming app on smart TVs. Unfortunately, integrating apps running of different devices is often not supported, instead manual effort or workarounds have to be used to increase the user experience across multiple devices. In our previous work [1, 2], we already developed an approach allowing to integrate services provided on Android devices into applications running on other devices. In this thesis, the approach shall be extended to other platforms, namely Windows, iOS, or MacOS.



  • Analyzing current means  for inter-application communication on one of the following platforms: Windows, iOS, or MacOS. 
  • Design of an approach to realize the cross-device integration of applications running on one of these platforms (e.g. by using adapters)
  • Implementation of a prototype which enables the cross-device integration for the respective platform and integrates with our current framework
  • Validating the approach by applying it for various applications


  • Familiar with Windows, MacOS, or iOS development
  • Having a device with the respective platform


[1] Dennis Wolters, Jonas Kirchhoff, Christian Gerth, Gregor Engels: Cross-Device Integration of Android Apps. In Proceedings of the 14th International Conference on Service Oriented Computing (ICSOC 2016). Springer, LNCS (2016) 

[2] Dennis Wolters, Jonas Kirchhoff, Christian Gerth, Gregor Engels: XDAI-A: Framework for Enabling Cross-Device Integration of Android Apps. In Proceedings of the 14th International Conference on Service Oriented Computing (ICSOC 2016). Springer, LNCS (2016)


Dennis Wolters



Ranking Constraint Violations in Knowledge Bases

Bearbeiter: noch nicht vergeben


- Motivation:

Knowledge bases such as Wikidata are used for a wide range of applications, e.g., quick

answer boxes in search engines (e.g. Google, Bing), personal assistants (e.g., Siri, Google),

or question answering systems (e.g., IBM Watson). However, today’s knowledge bases

suffer from quality problems. For example, Wikidata currently reports over 10 million

constraint violations. In traditional databases, all data which violates constraints is simply

discarded. However, this approach is not applicable to real-world, large-scale knowledge

bases as for almost every constraint, there is an exception in the real world, and strictly

enforcing constraints prevents an agile and flexible development of the knowledge base.

Nevertheless, constraint violations often point to quality problems. To overcome this

dilemma, we envision a semi-automatic approach: constraint violations are ranked by the

severity of their consequences, thus, enabling the volunteers of the knowledge base to manually review and fix the most important violations first.

- Description of the Task:

  • Investigate some examples of constraint violations in Wikidata, and manually order them by the severity of their consequences
  • Develop systematic criteria to rank constraint violations in knowledge bases
  • Develop a prototype for automatically ranking the constraint violations
  • Evaluate your prototype by comparing its result with your initial, manual ranking (or even perform a crowdsourcing experiment for master’s thesis)
  • For the most common and severe types of constraint violations, offer suggestions how to fix them (semi-) automatically

Kontakt: Stefan Heindorf

Anhang: ranking-constraint-violations-in-knowledge-bases.pdf

Die Universität der Informationsgesellschaft