@inproceedings{Graf2011Rolling,

title = {Rolling Boles, Optimal XML Structure Integrity for Updating Operations},

author = {Sebastian Graf and Sebastian Kay Belle and Marcel Waldvogel},

url = {https://netfuture.ch/wp-content/uploads/2011/graf11rolling.pdf},

year  = {2011},

date = {2011-03-28},

urldate = {1000-01-01},

booktitle = {Proceedings of the 20th international conference on World Wide Web (WWW2011)},

pages = {49-50},

publisher = {ACM},

address = {Hyderabad, India},

abstract = {While multiple techniques exist to utilize the tree structure of the Extensible Markup Language (XML) regarding integrity checks, they all rely on adaptions of the Merkle Tree: All children are acting as one slice regarding the checksum of one node with the help of an one-way hash concatenation. This results in postorder traversals regarding the (re-)computation of the integrity structure within modification operations. With our approach we perform nearly in-time updates of the entire integrity structure. We therefore equipped an XHash-based approach with an incremental hash function. This replaces postorder traversals by adapting only the incremental modifications to the checksums of a node and its ancestors. With experimental results we prove that our approach only generates a constant overhead depending on the depth of the tree while native DOMHash implementations produce an overhead based on the depth and the number of all nodes in the tree. Consequently, our approach called Rolling Boles generates sustainable impact since it facilitates instant integrity updates in constant time.},

keywords = {XML},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{Graf2011Hecate,

title = {Hecate: Managing Authorization with RESTful XML},

author = {Sebastian Graf and Vyacheslav Zholudev and Lukas Lewandowski and Marcel Waldvogel},

url = {https://netfuture.ch/wp-content/uploads/2011/graf11hecate.pdf},

year  = {2011},

date = {2011-03-28},

urldate = {1000-01-01},

booktitle = {Proceedings of WS-REST 2011},

abstract = {The potentials of REST offers new ways for communications between louse coupled entities featured through the Web of Things. The binding of the disjunct components of this architecture creates security issues, such as the centralized authorization techniques respecting the independence of the underlying entities. This results in the question how authorization is performed respecting the flexibility of REST without any knowledge about the underlying resources. Nevertheless, possible knowledge about these resources should enable the authorization workflow to offer finer-granular permissions on substructures of the resources. With our new approach - named Hecate - we offer a framework to assure simplified handling while keeping the potentials and flexibility of REST. We have designed an architecture based on XML with a flexible authorization mechanism on the one hand and optional resource-awareness on the other hand. The flexibility within the authorization work-flow bases on permission sets respecting the HTTP verbs. Additional in-depth knowledge of the entity optionally extends these permissions with resource-aware filters. Hecate offers not only great benefits because of its flexibility, but also because of the optional extensibility proved within the two reference implementations. With Hecate, we show that a centralized authorization mechanism combining independence and optional resource-based filtering extends the flexibility of REST rather than restricting it.},

keywords = {Identity Management, Security, XML},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{Graf2011Treetank,

title = {Treetank, Designing A Versioned XML Storage},

author = {Sebastian Graf and Marc Kramis and Marcel Waldvogel},

url = {https://netfuture.ch/wp-content/uploads/2011/graf11treetank.pdf},

year  = {2011},

date = {2011-03-26},

urldate = {1000-01-01},

booktitle = {XML Prague '11},

abstract = {XML underlies the same constant modification scenarios like any other resource especially in flexible environments like the WWW. Therefore, intelligent handling of versioned XML is mandatory. Due to the structural nature of XML, the efficient storage of changes in the data and therefor in the tree needs new paradigms regarding efficient storage and effective retrieval operations. We present a node granular XML versioning approach which relies on the independence of the storage and the versioning system. Different layers which have the ability to satisfy specific aspects of a node-granular versioning storage guarantee this independence. Results prove that our architecture offers efficient handling of consecutive changes within all modification scenarios while not restricting XML regarding its usage. Hence, our prototype system handles even huge XML instances while ensuring equal access to each revision of the data.},

keywords = {Cloud Storage, XML},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{Graf2010Integrity,

title = {Integrity Assurance for RESTful XML},

author = {Sebastian Graf and Lukas Lewandowski and Marcel Waldvogel},

url = {https://netfuture.ch/wp-content/uploads/2010/graf10integrity.pdf},

year  = {2010},

date = {2010-11-04},

urldate = {1000-01-01},

booktitle = {Proceedings of WISM 2010},

abstract = {The REpresentational State Transfer (REST) represents an extensible, easy and elegant architecture for accessing web-based resources. REST alone and in combination with XML is fast gaining momentum in a diverse set of web applications. REST is stateless, as is HTTP on which it is built. For many applications, this not enough, especially in the context of concurrent access and the increasing need for auditing and accountability. We present a lightweight mechanism which allows the application to control the integrity of the underlying resources in a simple, yet flexible manner. Based on an opportunistic locking approach, we show in this paper that XML does not only act as an extensible and direct accessible backend that ensures easy modifications due to the allocation of nodes, but also gives scalable possibilities to perform on-the-fly integrity verification based on the tree structure.},

keywords = {Security, XML},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{Graf2008Distributing,

title = {Distributing XML with Focus on Parallel Evaluation},

author = {Sebastian Graf and Marc Kramis and Marcel Waldvogel},

url = {https://netfuture.ch/wp-content/uploads/2008/graf08distributing.pdf},

year  = {2008},

date = {2008-08-23},

urldate = {1000-01-01},

booktitle = {Sixth International Workshop on Databases, Information Systems and Peer-to-Peer Computing (DBISP2P 2008)},

pages = {55-67},

abstract = {In contrast to relational databases the distribution of document-centric XML is not well researched. While there are some suggestions on how to split and distribute large XML documents, these approaches do not consider the parallel query evaluation. In this paper, we present and compare five different algorithms to search after suitable split nodes in

a large XML document. We then describe how to distribute extractable substructures over a fixed number of peers and how to query these peers in parallel to retrieve the final result. In addition, we analyse the impact of our splitting algorithms with respect to scalability for two different XPath expression classes on three well-known XML data sets. We conclude this paper with an outlook on future work, including result ordering during parallel query execution and dynamic re-distribution of XML fragments to new peers due to updates.},

keywords = {Cloud Storage, XML},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{Janetzko2006Exploring,

title = {Interactive Poster: Exploring Block Access Patterns of Native XML Storage},

author = {Halldór Janetzko and Daniel A. Keim and Marc Kramis and Florian Mansmann and Marcel Waldvogel},

url = {https://netfuture.ch/wp-content/uploads/2006/janetzko06exploring.pdf},

year  = {2006},

date = {2006-10-29},

urldate = {1000-01-01},

booktitle = {Proceedings of InfoVis 2006},

abstract = {Recent block-based native XML storage systems such as IDEFIX touch blocks according to the XQuery engine’s execution plan. The resulting access patterns are virtually unknown and potentially cause many expensive disk seeks. Visualization comes to the rescue when extensive log files must be analyzed – a tedious and difficult task. The dynamic time-based block-touch animation as well as the static block-type information of VISUAL IDEFIX foster the insight into the performance-critical internals of the XML storage and help to optimize both the block layout and the XQuery engine to speed up queries.},

keywords = {XML},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{Gruen2006Pushing,

title = {Pushing XPath Accelerator to its Limits},

author = {Christian Grün and Alexander Holupirek and Marc Kramis and Marc H. Scholl and Marcel Waldvogel},

url = {https://netfuture.ch/wp-content/uploads/2006/gruen06pushing.pdf},

year  = {2006},

date = {2006-06-01},

urldate = {1000-01-01},

booktitle = {Proceedings of the First International Workshop on Performance and Evaluation of Data Management Systems (EXPDB 2006)},

publisher = {ACM},

abstract = {<p>Two competing encoding concepts are known to scale well with growing amounts of XML data: XPath Accelerator encoding implemented by MonetDB for in-memory documents and X-Hive's Persistent DOM for on-disk storage. We identified two ways to improve XPath Accelerator and present prototypes for the respective techniques: BaseX boosts inmemory performance with optimized data and value index structures while Idefix introduces native block-oriented persistence with logarithmic update behavior for true scalability, overcoming main-memory constraints.</p><p>An easy-to-use Java-based benchmarking framework was developed and used to consistently compare these competing techniques and perform scalability measurements. The established XMark benchmark was applied to all four systems under test. Additional fulltext-sensitive queries against the well-known DBLP database complement the XMark results. Not only did the latest version of X-Hive finally surprise with good scalability and performance numbers. Also, both BaseX and Idefix hold their promise to push XPath Accelerator to its limits: BaseX efficiently exploits available main memory to speedup XML queries while Idefix surpasses main-memory constraints and rivals the on-disk leadership of X-Hive. The competition between XPath Accelerator and Persistent DOM definitely is relaunched.</p>},

keywords = {XML},

pubstate = {published},

tppubtype = {inproceedings}

}