Parsing XML Using Parallel Traversal of Streaming Trees

Abstract. XML has been widely adopted across a wide spectrum of applica-tions. Its parsing efficiency, however, remains a concern, and can be a bottleneck. With the current trend towards multicore CPUs, parallelization to improve per-formance is increasingly relevant. In many applications, the XML is streamed from the network, and thus the complete XML document is never in memory at any single moment in time. Parallel parsing of such a stream can be equated to parallel depth-first traversal of a streaming tree. Existing research on parallel tree traversal has assumed the entire tree was available in-memory, and thus cannot be directly applied. In this paper we investigate parallel, SAX-style parsing of XML via a parallel, depth-first traversal of the streaming document. We show good scalability up to about 6 cores on a Linux platform.

XML Messaging for Mobile Devices

In recent years, XML has been widely adopted as a universal format for structured data. A variety of XML-based systems have emerged, most prominently SOAP for Web services, XMPP for instant messaging, and RSS and Atom for content syndication. This popularity is helped by the excellent support for XML processing in many programming languages and by the variety of XML-based technologies for more complex needs of applications. Concurrently with this rise of XML, there has also been a qualitative expansion of the Internet's scope. Namely, mobile devices are becoming capable enough to be full-fledged members of various distributed systems. Such devices are battery-powered, their network connections are based on wireless technologies, and their processing capabilities are typically much lower than those of stationary computers. This dissertation presents work performed to try to reconcile these two developments. XML as a highly redundant text-based format is not obviously suitable for mobile devices that need to avoid extraneous processing and communication. Furthermore, the protocols and systems commonly used in XML messaging are often designed for fixed networks and may make assumptions that do not hold in wireless environments. This work identifies four areas of improvement in XML messaging systems: the programming interfaces to the system itself and to XML processing, the serialization format used for the messages, and the protocol used to transmit the messages. We show a complete system that improves the overall performance of XML messaging through consideration of these areas. The work is centered on actually implementing the proposals in a form usable on real mobile devices. The experimentation is performed on actual devices and real networks using the messaging system implemented as a part of this work. The experimentation is extensive and, due to using several different devices, also provides a glimpse of what the performance of these systems may look like in the future.Matkapuhelimien ja muiden mobiililaitteiden määrä on kasvanut erittäin nopeasti viime vuosina. Laitteiden pieni koko, niiden tarjoamat ohjelmointimahdollisuudet ja langattomat verkkoyhteydet mahdollistavat Internet- ja muiden verkkosovellusten käytön kaikkialla. Akusta johtuva rajallinen käyttöaika, heikko suoritusteho ja verkkokäytön vaatima virta ja aika toimivat kuitenkin selkeinä rajoitteina mobiililaitteiden mahdollisuuksille, ja jotta mobiilimaailma ei joutuisi kokonaan tulevaisuuden Internetin ulkopuolelle, järjestelmien ja sovellusten suunnittelussa on otettava sen erityispiirteet huomioon. Tulevaisuuden verkkosovelluksissa suoran päätelaitteiden välisen viestinnän odotetaan olevan keskeinen osa sovelluksen toimintaa. Nyky-Internetissä tällaisessa viestinnässä käytetään yhä useammin XML-kieltä, joka laajennettavuutensa ja helppokäyttöisyytensä ansiosta vähentää sovelluskehittäjän taakkaa. XML-kielen ongelmina ovat kuitenkin sen vaatimat suuret tiedonsiirto- ja käsittelyajat, jotka ovat olleet esteenä XML:n laajalle käytölle mobiiliympäristöissä. Väitöskirja tutkii XML-pohjaisen laitteiden välisen viestinnän perusedellytyksiä mobiililaitteilla langattomissa verkoissa. Keskeiset tutkimuskohteet ovat tiivis ja tehokkaasti käsiteltävä XML-esitysmuoto, XML:n käsittelyyn paremmin sopivat ohjelmointirajapinnat ja mobiiliympäristön viestiprotokollat. Työn tuloksena on syntynyt mobiililaitteille suunniteltu XML-pohjainen viestintäjärjestelmä, joka on sellaisenaan käytettävissä verkkosovellusten perustana. Järjestelmälle on suoritettu kattavat mittaukset, jotka osoittavat järjestelmän sopivuuden käyttötarkoitukseensa. Tulosten analyysissa otetaan myös huomioon, miten järjestelmän eri ominaisuudet sopivat kuhunkin mobiililaitteiden tukemaan ympäristöön, sekä tarkastellaan, miltä tulevaisuuden mobiililaitteiden suorituskyky saattaisi näyttää

Pentagonal scheme for dynamic XML prefix labelling

In XML databases, the indexing process is based on a labelling or numbering scheme and generally used to label an XML document to perform an XML query using the path node information. Moreover, a labelling scheme helps to capture the structural relationships during the processing of queries without the need to access the physical document. Two of the main problems for labelling XML schemes are duplicated labels and the cost efficiency of labelling time and size. This research presents a novel dynamic XML labelling scheme, called the Pentagonal labelling scheme, in which data are represented as ordered XML nodes with relationships between them. The update of these nodes from large scale XML documents has been widely investigated and represents a challenging research problem as it means relabelling a whole tree. Our algorithms provide an efficient dynamic XML labelling scheme that supports data updates without duplicating labels or relabelling old nodes. Our work evaluates the labelling process in terms of size and time, and evaluates the labelling scheme’s ability to handle several insertions in XML documents. The findings indicate that the Pentagonal scheme shows a better initial labelling time performance than the compared schemes, particularly when using large XML datasets. Moreover, it efficiently supports random skewed updates, has fast calculations and uncomplicated implementations so efficiently handles updates. Also, it proved its capability in terms of the query performance and in determining the relationships.Libyan governmen

Enhanced web services performance by compression and similarity-based aggregation of SOAP traffic

Many organizations around the world have adopted Web services, server farms hosted by large enterprises, and data centres for various applications. Web services offer several advantages over other communication technologies. However, it still has high latency and often suffers congestion and bottlenecks due to the massive load generated by large numbers of end users for Web service requests. Simple Object Access Protocol (SOAP) is the basic Extensible Markup Language (XML) communication protocol of Web services that is widely used over the Internet. SOAP provides interoperability by establishing access among Web servers and clients from the same or different platforms. However, the verbosity of the XML format and its encoded messages are often larger than the actual payload, causing dense traffic over the network. This thesis is proposing three innovative techniques capable of reducing small, as well as very large, messages. Furthermore, new redundancy-aware SOAP Web message aggregation models (Binary-tree, Two-bit, and One-bit XML status trees) are proposed to enable the Web servers to aggregate SOAP responses, and send them back as one compact aggregated message, thereby reducing the required bandwidth and latency, and improving the overall performance of Web services. Fractal as a mathematical model provides powerful self-similarity measurements for the fragments of regular and irregular geometric objects in their numeric representations. Fractal mathematical parameters are introduced to compute SOAP message similarities that are applied on the numeric representation of SOAP messages. Furthermore, SOAP fractal similarities are developed to devise a new unsupervised auto-clustering technique. Fast fractal similarity based clustering technique is proposed with the aim of speeding up the computations for the selection of similar messages to be aggregated together in order to achieve greater reduction

Compressing Labels of Dynamic XML Data using Base-9 Scheme and Fibonacci Encoding

The flexibility and self-describing nature of XML has made it the most common mark-up language used for data representation over the Web. XML data is naturally modelled as a tree, where the structural tree information can be encoded into labels via XML labelling scheme in order to permit answers to queries without the need to access original XML files. As the transmission of XML data over the Internet has become vibrant, it has also become necessary to have an XML labelling scheme that supports dynamic XML data. For a large-scale and frequently updated XML document, existing dynamic XML labelling schemes still suffer from high growth rates in terms of their label size, which can result in overflow problems and/or ambiguous data/query retrievals. This thesis considers the compression of XML labels. A novel XML labelling scheme, named “Base-9”, has been developed to generate labels that are as compact as possible and yet provide efficient support for queries to both static and dynamic XML data. A Fibonacci prefix-encoding method has been used for the first time to store Base-9’s XML labels in a compressed format, with the intention of minimising the storage space without degrading XML querying performance. The thesis also investigates the compression of XML labels using various existing prefix-encoding methods. This investigation has resulted in the proposal of a novel prefix-encoding method named “Elias-Fibonacci of order 3”, which has achieved the fastest encoding time of all prefix-encoding methods studied in this thesis, whereas Fibonacci encoding was found to require the minimum storage. Unlike current XML labelling schemes, the new Base-9 labelling scheme ensures the generation of short labels even after large, frequent, skewed insertions. The advantages of such short labels as those generated by the combination of applying the Base-9 scheme and the use of Fibonacci encoding in terms of storing, updating, retrieving and querying XML data are supported by the experimental results reported herein

Web service control of component-based agile manufacturing systems

Current global business competition has resulted in significant challenges for manufacturing and production sectors focused on shorter product lifecyc1es, more diverse and customized products as well as cost pressures from competitors and customers. To remain competitive, manufacturers, particularly in automotive industry, require the next generation of manufacturing paradigms supporting flexible and reconfigurable production systems that allow quick system changeovers for various types of products. In addition, closer integration of shop floor and business systems is required as indicated by the research efforts in investigating "Agile and Collaborative Manufacturing Systems" in supporting the production unit throughout the manufacturing lifecycles. The integration of a business enterprise with its shop-floor and lifecycle supply partners is currently only achieved through complex proprietary solutions due to differences in technology, particularly between automation and business systems. The situation is further complicated by the diverse types of automation control devices employed. Recently, the emerging technology of Service Oriented Architecture's (SOA's) and Web Services (WS) has been demonstrated and proved successful in linking business applications. The adoption of this Web Services approach at the automation level, that would enable a seamless integration of business enterprise and a shop-floor system, is an active research topic within the automotive domain. If successful, reconfigurable automation systems formed by a network of collaborative autonomous and open control platform in distributed, loosely coupled manufacturing environment can be realized through a unifying platform of WS interfaces for devices communication. The adoption of SOA- Web Services on embedded automation devices can be achieved employing Device Profile for Web Services (DPWS) protocols which encapsulate device control functionality as provided services (e.g. device I/O operation, device state notification, device discovery) and business application interfaces into physical control components of machining automation. This novel approach supports the possibility of integrating pervasive enterprise applications through unifying Web Services interfaces and neutral Simple Object Access Protocol (SOAP) message communication between control systems and business applications over standard Ethernet-Local Area Networks (LAN's). In addition, the re-configurability of the automation system is enhanced via the utilisation of Web Services throughout an automated control, build, installation, test, maintenance and reuse system lifecycle via device self-discovery provided by the DPWS protocol...cont'd

Generating and Managing Secure Passwords for Online Accounts

User accounts at Internet services contain a multitude of personal data such as messages, documents, pictures, and payment information. Passwords are used to protect these data from unauthorized access. User authentication based on passwords has many advantages for both users and service providers. Users can use passwords across many platforms, devices, and applications and do not need to carry an additional device. Service providers can implement password-based user authentication with little effort and operate it with low cost per user. However, passwords have a key problem: the conflict between security and ease of use. For security reasons, passwords must be attack-resistant, individual for each account, and changed on a regular basis. But, these security requirements make passwords very difficult to use. They require users to create and manage a large portfolio of passwords. This poses three problems: First, the generation of attack-resistant passwords is very difficult. Second, the memorization of many passwords is practically impossible. Third, the regular change of passwords is very time-consuming. These problems are aggravated by the different password requirements, interfaces, and procedures of services. The preservation of passwords for users such as storing passwords on user devices mitigates the memorization problem, but it raises new problems: the confidentiality, availability, recoverability, and accessibility of the preserved passwords. Despite decades of research, the problems of passwords are not solved yet. Consequently, secure passwords are not usable in practice. As a result, users select weak passwords, use them across accounts, and barely change them. In this thesis, we introduce the Password Assistance System (PAS). It makes secure passwords usable for users. This is achieved by automation and comprehensive support. PAS covers all aspects of passwords. It generates, preserves, and changes passwords for users as well as ensures the confidentiality, availability, recoverability, and accessibility of the preserved passwords. This reduces the efforts and activities of users to deal with passwords to a minimum and thus enables users to practically realize secure passwords for their online accounts for the first time. PAS is the first solution that is capable of handling the different password implementations of services. This is achieved by a standardized description of password requirements, interfaces, and procedures. Moreover, PAS is solely realized on the user-side and requires no changes on the service-side. Both features ensure the practicability of PAS and make it ready to be used. PAS solves the password generation problem by creating attack-resistant, individual, and valid passwords for users automatically. Users just need to provide the URL of a service to generate an optimal password for an account. Our uniform description of password requirements provides the information to generate passwords in accordance with the individual password requirements of services. PAS is able to generate the requirements descriptions automatically by extracting the password requirements of services from their websites. So far, this was done for 185,696 services. Moreover, PAS is equipped with an optimal password-composition rule set for the event that services do not explicitly state their password requirements, which is the usual case. By means of the optimal rule set, PAS also generates attack-resistant passwords with the best possible acceptance rate in case of unknown password requirements. PAS solves the password memorization problem by preserving passwords for users. This releases users from memorizing their passwords and facilitates to use individual passwords for accounts. PAS makes users' password portfolios available on all their devices as well as automatically synchronizes changes. PAS achieves this without storing passwords at servers so that an attacker cannot steal them from servers. Moreover, PAS provides a backup solution to recover the preserved passwords in case of loss. Users need to create backups only once and do not have to update them even when their password portfolios change. Consequently, users can keep backups completely offline at secure, different, and physically isolated locations. This minimizes the risk of compromise and loss as well as enables an emergency access to the passwords for trusted persons. Moreover, PAS has a built-in revocation mechanism. It allows users to completely invalidate devices and backups in case they lose control over them. This guarantees that no passwords can be stolen from lost user devices and backups once revoked. Users always have full control of their passwords. PAS solves the password change problem by changing passwords automatically for users. Users neither need to create new passwords nor manually log in to their accounts. Our uniform description of password interfaces and procedures provides the information to change passwords at arbitrary services. Moreover, PAS is the first solution that provides autonomous password changes. It changes passwords on a regular basis with respect to the security level of passwords as well as immediately after PAS detects a compromise of users' passwords. The practicability of PAS is demonstrated by an implementation. The individual components of PAS can be used independently, integrated into other applications, and combined to a single user application, called a password assistant. In summary, this thesis presents a solution that makes secure passwords usable. This is done by automation and comprehensive support in the generation and management of passwords

Enhanced SOAP Performance for low bandwidth environments

It is desirable that SOAP performs efficiently in environments where there are a large number of transactions. However, SOAP is based on XML and therefore inherits XML's disadvantage of having voluminous messages. Firstly, the performance of different SOAP bindings is investigated. A benchmark of different SOAP bindings in wireless environments demonstrates the unsuitability of HTTP and TCP bindings in limited bandwidth environments. UDP is recommended as an alternative transport protocol for SOAP. Secondly, the thesis examines the use of multicast in reducing the traffic caused by SOAP messages in low bandwidth environments to deal with challenges described. A novel SOAP-level multicast protocol based on the similarity of SOAP messages, called SMP (Similarity-based SOAP Multicast Protocol), is proposed. In particular, issues of traffic, network optimization, response time and scalability are investigated. Lastly, two extensions of SMP are proposed to further improve the performance of SMP. SMP's extensions are two algorithms, greedy and incremental tc-SMP, for traffic-constrained similarity-based SOAP multicast. Tc-SMP optimizes network traffic by building its own spanning trees instead of using the one built by traditional methods, such as Dijkstra's algorithm. A new client is added to a tc-SMP tree through an existing tc-SMP node that causes minimal additional traffic for that connection. Detailed analytical models and experimental evaluations of the proposed methods demonstrate that combining SOAP messages of similar content and multicasting them as aggregated messages can significantly lower total network traffic. These improvements are advantageous for Web service applications that involve a high number of simultaneous similar transactions such as stock quotes, weather and sport event reports