WAQL-PP: Preprocessor for a Data Aggregation Query Language
This week I started to design and implement a preprocessor for the Web-service Aggregation Query Language (WAQL) which is an extension of XQuery. This language is used as part of the WS-Aggregation framework developed at the Distributed Systems Group of the Vienna University of Technology. With this text I want to explain the motivation behind WAQL and how the preprocessor will be designed. The motivation is nicely stated as part of my task description.
The key idea of WAQL is that it provides a convenience syntax for XQuery, which otherwise tends to become complex and hardly comprehensible in bigger scenarios. WAQL queries are transformed into valid XQuery expressions, which are finally executed by a (third-party) XQuery engine.
First of all we need to get a grasp of what the WAQL extensions to the XQuery language are. Since WAQL is still in its experimental stages, there is no exact specification of the language and it may change or grow over time. At the moment WAQL consists of two language constructs:
- Template Lists: This extension tries to simplify the specification of generated inputs. It basically is syntactical sugar representing a XQuery for-loop construct and as such can be transformed easily.
- Data Dependencies: This second extension is the interesting one, it can express dependencies between several different queries. The framework has to identify these dependencies and execute the queries in a valid order, so that all dependencies can be resolved.
The above two constructs should explain why the actual transformation has to be split into several phases which can be triggered by the framework at different points in time. The separate steps the preprocessor has to perform are as follows:
- Parsing: The textual WAQL query is parsed and an intermediate representation is constructed. Since WAQL is an extension which enhances the set of expressions for the XQuery language, the actual parser has to understand the full XQuery grammar. This may sound like a lot of work, but the XQuery specification provides a detailed description of the grammar in about 140 EBNF rules. So defining a valid parser is a doable job.
- Resolving of data dependencies: At this point the preprocessor has generated a list of all unresolved data dependencies. However the preprocessor has no idea which other queries are linked to the one currently being processed. So the actual resolving has to be done by the framework, the preprocessor just adapts the intermediate representation to the data provided by the framework.
- Transformation: Once all dependencies have been resolved the intermediate representation can be transformed back into a textual XQuery (without any WAQL extensions), which can then be passed on to a third-party XQuery engine.
Now that the basic operations are defined, we are able to give a rough description of the WAQL preprocessor and how it can be embedded into the existing framework. The two basic modules are a generated parser (obviously performing the parsing step) and a driving engine (performing the resolving and transformation steps). The parser will most certainly be generated using the JavaCC parser generator. The below graphic should explain the architecture.
Note that the above explanation is written from the compiler-constructor point of view, it just covers the preprocessor as part of the framework. All the other nasty details of WS-Aggregation are beyond the scope of this text. If you are interested you should read the paper or contact Waldemar Hummer who was kind enough to explain it to me. Also I will continue to write about the ongoing development of the preprocessor, so stay tuned.
Update: This text was crossposted to the DSG Praktika Blog as well.
Pingback
great analysis , very
great analysis , very informative
Pingback
Magnificent goods from you,
Magnificent goods from you, man. I've take note
your stuff previous to and you are just extremely excellent.
I actually like what you've received right here, really like what you are stating and the best way through which you say it.
You are making it enjoyable and you continue to care for to keep it smart.
I can not wait to learn much more from you.
That is actually a wonderful website.
So I just behave for
So I just behave for https://privateinvestigatorindianapolis.com
Now are you talking about the
Now are you talking about the WAQL-PP.2.0 processor or the Vienna University technology professors?
This is a fantastic website
This is a fantastic website and I can not recommend you guys enough.
Hello mates, how is all, and
Hello mates, how is all, and what you want to say about this piece of writing,
in my view its actually remarkable designed for me.
whoah this blog is wonderful
whoah this blog is wonderful i love reading your posts.
Keep up the good work! You already know, many individuals
are looking round for this info, you can help them greatly. https://angel.co/u/james-land-1
Cégvásárlás iránt érdeklődők
Cégvásárlás iránt érdeklődők és befektetők számára dealmarket eladó cégek listája adatbázis.
Revolutionize Your Workspace
Revolutionize Your Workspace with Freedman's Office Chairs in Atlanta
**Embrace Productivity and Comfort: Freedman's Office Chairs in Atlanta**
In the bustling city of Atlanta, where innovation meets tradition, Freedman's Office Furniture
introduces its exclusive range of ergonomic
office chairs. Located at 3379 Peachtree Rd NE,
Atlanta, GA 30326, our showroom caters to the discerning
tastes of residents in neighborhoods like Ansley Park and Baker Hills, offering premium office seating solutions that combine
style and functionality.
**Elevate Your Workspace in the Heart of Atlanta**
Atlanta, founded in 1836, stands as a testament
to a rich history and a thriving metropolis. With a
population of 496,461 (2021) and 227,388 households, the city continues to evolve while preserving
its unique charm. Freedman's commitment to providing modern office chairs aligns seamlessly with Atlanta's
spirit of progress and dynamism.
**Navigating the Urban Hub: Interstate 20**
Much like the smooth flow of Interstate 20, Freedman's ergonomic office chairs embody a perfect blend of form and function. This mirrors Atlanta's commitment to providing a conducive environment for businesses to flourish and
individuals to excel in their professional endeavors.
**Investing in Style: A Wise Choice for Atlanta Professionals**
In a city that values aesthetics and innovation, opting for Freedman's ergonomic office chairs is a
statement of sophistication. Our collection not only
enhances the visual appeal of your workspace but also complements Atlanta's commitment
to creating a work environment that fosters creativity and success.
**Discovering Atlanta's Landmarks and the Comfort of Freedman's Chairs**
Embark on a journey through Atlanta's iconic landmarks while experiencing the unmatched comfort of Freedman's ergonomic
office chairs. Here are five fascinating facts about some of Atlanta's
cherished destinations:
- **Atlanta Botanical Garden:** A 30-acre botanical garden showcasing an incredible variety
of plants and flowers.
- **Centennial Olympic Park:** Built for
the 1996 Summer Olympics, this park serves as a gathering spot for locals and visitors.
- **Atlanta History Center:** An extensive history museum featuring exhibits, historic houses, and gardens.
- **College Football Hall of Fame:** Celebrating the rich history of college football
with interactive exhibits and memorabilia.
- **The ""It's a living"" Street Art:** A vibrant street art
scene in the city, offering colorful and dynamic murals.
**Why Choose Freedman's Ergonomic Office Chairs in Atlanta**
Opting for Freedman's ergonomic office chairs in Atlanta is
not just a choice; it's a commitment to elevate your workspace.
Our stylish and comfortable chairs ensure that your office reflects the vibrant and dynamic spirit of Atlanta, making it an ideal place for productivity, innovation, and success.
"
"Transform Your Work Environment with Freedman's Office Chairs in Orlando
**Revitalize Your Workspace: Discover Freedman's Office Chairs in Orlando**
In the heart of Orlando, where magic and modernity coexist, Freedman's
Office Furniture proudly presents its exclusive range of office
chairs. Conveniently located at 200 E Robinson St Suite 1120, Orlando, FL 32801,
our showroom caters to the diverse needs of residents in neighborhoods like Audubon Park and Colonial Town Center,
offering premium office seating solutions that prioritize both comfort and style.
**Elevate Your Work Experience in Orlando's Lively Atmosphere**
Orlando, founded in 1875, has grown into a vibrant city with a population of 309,
154 (2021) and 122,607 households. Freedman's commitment to providing high-quality office chairs
resonates with Orlando's lively and energetic atmosphere,
offering residents the perfect blend of comfort and functionality for their
workspaces.
**Navigating the City: The Significance of Interstate 4**
Much like the seamless flow of Interstate 4, Freedman's ergonomic office chairs seamlessly blend style and functionality.
This mirrors Orlando's commitment to providing an environment where residents can seamlessly navigate between work and leisure,
making our chairs an ideal choice for those who value efficiency and
aesthetics.
**Investing in Comfort: An Informed Choice for Orlando
Professionals**
In a city known for its diverse attractions and entertainment, investing in Freedman's
ergonomic office chairs is a conscious decision. Our chairs not only enhance the aesthetics of your workspace but also align with
Orlando's commitment to providing a comfortable
and conducive work environment.
**Explore Orlando's Attractions and Relax in Freedman's Chairs**
Embark on a journey through Orlando's enchanting attractions while enjoying the unparalleled comfort of Freedman's ergonomic office chairs.
Here are five interesting facts about some of Orlando's most beloved landmarks:
- **Walt Disney World Resort:** The most visited vacation resort globally, spanning over 25,
000 acres.
- **Universal Studios Florida:** An iconic film and
television studio theme park, featuring thrilling rides and attractions.
- **Lake Eola Park:** A scenic park in downtown Orlando with a picturesque lake and swan boats.
- **Dr. Phillips Center for the Performing Arts:** A state-of-the-art venue hosting
various cultural and artistic performances.
- **Orlando Museum of Art:** Showcasing a diverse collection of contemporary and classic art.
**Why Choose Freedman's Ergonomic Office Chairs in Orlando**
Opting for Freedman's ergonomic office chairs in Orlando is not just a decision; it's a commitment to enhancing your workspace.
Our stylish and comfortable chairs ensure that your office reflects the dynamic and creative spirit of
Orlando, making it an ideal place for productivity, innovation,
and success.
"
"Discover Superior Comfort with Freedman's
Office Chairs in Atlanta
**Elevate Your Workspace: Freedman's Office Chairs in Atlanta**
Nestled in the vibrant city of Atlanta, Freedman's Office Furniture proudly introduces its exclusive collection of office
chairs. Conveniently located at 3379 Peachtree Rd NE, Atlanta, GA 30326, our
showroom caters to the diverse needs of residents in neighborhoods like Ansley Park and Buckhead, offering premium office seating solutions that blend comfort and sophistication seamlessly.
**Crafting a Distinctive Workspace in Atlanta's Dynamic Setting**
Founded in 1836, Atlanta has evolved into a bustling city with a population of 496,461 (2021) and 227,
388 households. Freedman's commitment to delivering top-notch office chairs aligns perfectly with
Atlanta's dynamic and diverse setting, providing residents with ergonomic solutions
that enhance both productivity and aesthetic appeal.
**Navigating the Urban Hub: The Importance of Interstate 20**
Much like the flow of Interstate 20, Freedman's ergonomic office chairs effortlessly navigate the modern office landscape.
This reflects Atlanta's status as a vibrant urban hub, where residents value efficiency and
style in equal measure, making our chairs the perfect choice for
those seeking a superior seating experience.
**Investing in Excellence: A Thoughtful Choice for Atlanta Professionals**
In a city renowned for its rich history and cultural attractions, choosing Freedman's ergonomic office chairs is a thoughtful
investment. Our chairs not only elevate the visual appeal
of your workspace but also resonate with Atlanta's
commitment to fostering innovation and success through a comfortable and ergonomic work environment.
**Explore Atlanta's Cultural Gems and Relax in Freedman's Chairs**
Immerse yourself in Atlanta's cultural richness while enjoying the superior
comfort of Freedman's ergonomic office chairs. Here are five fascinating facts
about some of Atlanta's most iconic landmarks:
- **Atlanta Botanical Garden:** A 30-acre garden showcasing an incredible variety
of plants, flowers, and sculptures.
- **Centennial Olympic Park:** Built for the 1996 Summer Olympics,
it's a gathering spot with fountains, events, and green spaces.
- **Martin Luther King Jr. National Historic Site:** Preserving
the legacy of the civil rights leader, including his childhood
home and Ebenezer Baptist Church.
- **Piedmont Park:** A sprawling urban park with walking trails, sports facilities, and the picturesque Lake Clara Meer.
- **The Fox Theatre:** A historic venue known for
its Moorish architecture and hosting various performances.
**Why Choose Freedman's Ergonomic Office Chairs in Atlanta**
Opting for Freedman's ergonomic office chairs in Atlanta is not merely a decision—it's
a statement. Elevate your workspace with our stylish and
comfortable chairs, embodying the spirit of innovation and success that defines Atlanta's dynamic professional landscape.
"
"Discover Unmatched Seating Comfort with Freedman's Office Chairs in Orlando
**Elevate Your Workspace: Freedman's Office Chairs in Orlando**
Located at 200 E Robinson St Suite 1120, Orlando, FL 32801,
Freedman's Office Furniture is proud to introduce its
exclusive range of office chairs to the vibrant city of
Orlando. Serving neighborhoods like Colonial Town Center and College Park, Freedman's provides superior office seating solutions that prioritize both comfort and
style.
**Crafting a Distinctive Workspace in Orlando's Sunshine State**
Established in 1875, Orlando has transformed into a thriving city
with a 2021 population of 309,154 and 122,607 households.
Freedman's dedication to delivering top-tier office chairs aligns seamlessly with
Orlando's sunny ambiance, offering residents ergonomic
solutions that blend seamlessly with the
city's dynamic and energetic atmosphere.
**Navigating the Urban Landscape: The Significance of Interstate 4**
Much like the flow of Interstate 4, Freedman's
ergonomic office chairs effortlessly navigate the modern office
landscape. This mirrors Orlando's status as
a hub of entertainment and technology, where residents seek innovative
and comfortable seating solutions, making our chairs the ideal choice for those desiring a superior seating experience.
**Investing in Excellence: A Thoughtful Choice for Orlando Professionals**
In a city known for its theme parks and cultural attractions,
choosing Freedman's ergonomic office chairs is a thoughtful investment.
Our chairs not only enhance the visual appeal of your workspace but
also align with Orlando's commitment to creating a vibrant
and comfortable work environment that fosters creativity
and success.
**Explore Orlando's Magical Attractions and Relax in Freedman's Chairs**
Immerse yourself in Orlando's magical offerings while enjoying the
unmatched comfort of Freedman's ergonomic office chairs.
Here are five fascinating facts about some of Orlando's most
iconic landmarks:
- **Walt Disney World Resort:** The world's most-visited vacation resort, featuring four theme parks and numerous attractions.
- **Universal Studios Florida:** A film and television studio theme park with thrilling rides and shows.
- **Lake Eola Park:** A downtown oasis with swan boats,
live swans, and scenic walking paths.
- **Orlando Science Center:** A hands-on science museum with interactive exhibits and engaging displays.
- **Dr. Phillips Center for the Performing Arts:
** A modern venue hosting various live performances, including Broadway
shows.
**Why Choose Freedman's Ergonomic Office
Chairs in Orlando**
Opting for Freedman's ergonomic office chairs in Orlando is more than just a decision—it's
a commitment to excellence. Elevate your workspace with our stylish and comfortable chairs, embodying the spirit of innovation and success that defines Orlando's dynamic professional landscape.
"
"Revolutionize Your Workspace with Freedman's Office Chairs in Atlanta
**Experience Unparalleled Comfort: Freedman's Office Chairs in Atlanta**
Nestled at 3379 Peachtree Rd NE, Atlanta, GA 30326, Freedman's Office Furniture proudly introduces its exceptional collection of office chairs to the dynamic city of Atlanta.
Serving neighborhoods like Ansley Park and Buckhead, Freedman's delivers office seating solutions that seamlessly combine ergonomic
design with aesthetic appeal.
**Redesigning Your Office Aesthetic: Freedman's Office Chairs in Atlanta**
Founded in 1836, Atlanta has evolved into a bustling metropolis with a 2021 population of 496,461 and 227,388 households.
Freedman's commitment to providing top-notch office
chairs perfectly complements Atlanta's modern and diverse atmosphere, offering residents seating solutions that embody both innovation and style.
**Navigating the Cityscape: The Significance of Interstate 20**
Much like the connectivity provided by Interstate
20, Freedman's ergonomic office chairs seamlessly integrate into Atlanta's diverse professional landscape.
Reflecting Atlanta's status as a cultural and economic hub, our chairs offer
residents unparalleled comfort and style, making them the preferred choice for those seeking an exceptional
seating experience.
**A Commitment to Excellence: Choosing Freedman's Chairs in Atlanta**
In a city known for its rich history and cultural landmarks, choosing Freedman's ergonomic
office chairs is a statement of commitment to excellence.
Our chairs not only enhance the visual appeal of your workspace but also align with Atlanta's reputation for fostering innovation and success.
**Explore Atlanta's Rich Heritage and Relax in Freedman's Chairs**
Discover the vibrant history of Atlanta while enjoying the unrivaled comfort of Freedman's ergonomic office
chairs. Here are five intriguing facts about some of Atlanta's iconic landmarks:
- **Atlanta History Center:** A comprehensive history museum
featuring exhibits on the Civil War and Southern history.
- **Piedmont Park:** Atlanta's premier green space, offering walking
paths, sports facilities, and beautiful scenery.
- **Martin Luther King Jr. National Historic Site:** Preserving the childhood home of the civil rights leader and featuring the
Ebenezer Baptist Church.
- **The Fox Theatre:** A historic performing arts venue known for its grand architecture and
diverse entertainment.
- **The High Museum of Art:** Atlanta's leading art museum, showcasing a diverse
collection of artwork.
**Why Freedman's Ergonomic Office Chairs Stand Out in Atlanta**
Choosing Freedman's ergonomic office chairs in Atlanta is a decision that transcends mere furniture.
It's a commitment to elevating your workspace with stylish and comfortable seating that resonates with Atlanta's spirit
of progress and achievement.
A fantastic source of
A fantastic source of information. Thank you for taking the time to address this; I have strong feelings about it and would like to learn more about it.
Great read. Thanks for
Great read. Thanks for sharing this information.
Nice replies in return of
Nice replies in return of this issue with solid arguments and explaining the whole thing regarding that.
Yeah, right? I love reading
Yeah, right? I love reading this too! so informational! IF you are looking for angels, take a look at our gallery of newborns! They are literally so adorable like an angel.
check us out at www.sanjosebabyphotos.com/
This is really informative.
This is really informative. Very helpful.
It's an amazing paragraph for
It's an amazing paragraph for all the online users; they will take benefit from
it I am sure.
I agree, the content was
I agree, the content was helpful, especially for developers.