Optimizing the performance of a relational algebra database interface
Communications of the ACM
A relational model of data for large shared data banks
Communications of the ACM
An Introduction to Database Systems
An Introduction to Database Systems
The Design and Analysis of Computer Algorithms
The Design and Analysis of Computer Algorithms
Optimal implementation of conjunctive queries in relational data bases
STOC '77 Proceedings of the ninth annual ACM symposium on Theory of computing
Formal languages and their relation to automata
Formal languages and their relation to automata
The Format Model: A Theory of database Organization
Journal of the ACM (JACM)
Implementation of logical query languages for databases
ACM Transactions on Database Systems (TODS)
A framework for choosing a database query language
ACM Computing Surveys (CSUR)
The design of a relational database system with abstract data types for domains
ACM Transactions on Database Systems (TODS)
Generating editing environments based on relations and attributes
ACM Transactions on Programming Languages and Systems (TOPLAS)
MATCH—a new high-level relational operator for pattern matching
Communications of the ACM
Logic and databases: a critique
ACM SIGACT News
On the integrity of databases with incomplete information
PODS '86 Proceedings of the fifth ACM SIGACT-SIGMOD symposium on Principles of database systems
Data independent recursion in deductive databases
PODS '86 Proceedings of the fifth ACM SIGACT-SIGMOD symposium on Principles of database systems
Parallel evaluation of recursive rule queries
PODS '86 Proceedings of the fifth ACM SIGACT-SIGMOD symposium on Principles of database systems
Language constructs for programming by example
COCS '86 Proceedings of the third ACM-SIGOIS conference on Office information systems
An amateur's introduction to recursive query processing strategies
SIGMOD '86 Proceedings of the 1986 ACM SIGMOD international conference on Management of data
A message passing framework for logical query evaluation
SIGMOD '86 Proceedings of the 1986 ACM SIGMOD international conference on Management of data
Traversal recursion: a practical approach to supporting recursive applications
SIGMOD '86 Proceedings of the 1986 ACM SIGMOD international conference on Management of data
Evaluation of database recursive logic programs as recurrent function series
SIGMOD '86 Proceedings of the 1986 ACM SIGMOD international conference on Management of data
Query processing in deductive databases with incomplete information
SIGMOD '86 Proceedings of the 1986 ACM SIGMOD international conference on Management of data
Logic and databases: a response
ACM SIGACT News
Logic and databases: a critique
ACM SIGPLAN Notices
Logic and databases: a response
ACM SIGPLAN Notices
The decision problem for the probabilities of higher-order properties
STOC '87 Proceedings of the nineteenth annual ACM symposium on Theory of computing
Database theory—past and future
PODS '87 Proceedings of the sixth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
PODS '87 Proceedings of the sixth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Bounds on the propagation of selection into logic programs
PODS '87 Proceedings of the sixth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
A translation language complete for database update and specification
PODS '87 Proceedings of the sixth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Efficient evaluation for a subset of recursive queries
PODS '87 Proceedings of the sixth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
On the expressive power of the extended relational algebra for the unnormalized relational model
PODS '87 Proceedings of the sixth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
PODS '87 Proceedings of the sixth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Querying part hierarchies: a knowledge-based approach
DAC '87 Proceedings of the 24th ACM/IEEE Design Automation Conference
A graphical query language supporting recursion
SIGMOD '87 Proceedings of the 1987 ACM SIGMOD international conference on Management of data
Mechanical translation of set theoretic problem specifications into efficient RAM code-A case study
Journal of Symbolic Computation
Types and persistence in database programming languages
ACM Computing Surveys (CSUR)
The powerset algebra as a result of adding programming constructs to the nested relational algebra
SIGMOD '88 Proceedings of the 1988 ACM SIGMOD international conference on Management of data
Compiling separable recursions
SIGMOD '88 Proceedings of the 1988 ACM SIGMOD international conference on Management of data
SIGMOD '88 Proceedings of the 1988 ACM SIGMOD international conference on Management of data
Alpha: An Extension of Relational Algebra to Express a Class of Recursive Queries
IEEE Transactions on Software Engineering
SYGRAF: Implementing Logic Programs in a Database Style
IEEE Transactions on Software Engineering
INC: a language for incremental computations
PLDI '88 Proceedings of the ACM SIGPLAN 1988 conference on Programming Language design and Implementation
Minimizing function-free recursive inference rules
Journal of the ACM (JACM)
Decidable optimization problems for database logic programs
STOC '88 Proceedings of the twentieth annual ACM symposium on Theory of computing
An approach to the recursive retrieval problem in the relational database
Communications of the ACM
The Computational Completeness of Extended Database Query Languages
IEEE Transactions on Software Engineering
ODE (Object Database and Environment): the language and the data model
SIGMOD '89 Proceedings of the 1989 ACM SIGMOD international conference on Management of data
Conflict resolution of rules assigning values to virtual attributes
SIGMOD '89 Proceedings of the 1989 ACM SIGMOD international conference on Management of data
Efficient evaluation of right-, left-, and multi-linear rules
SIGMOD '89 Proceedings of the 1989 ACM SIGMOD international conference on Management of data
Expressiveness of restricted recursive queries
STOC '89 Proceedings of the twenty-first annual ACM symposium on Theory of computing
On the first-order expressibility of recursive queries
PODS '89 Proceedings of the eighth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Expressibility of bounded-arity fixed-point query hierarchies
PODS '89 Proceedings of the eighth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Expressing structural hypertext queries in graphlog
HYPERTEXT '89 Proceedings of the second annual ACM conference on Hypertext
Linearization of Nonlinear Recursive Rules
IEEE Transactions on Software Engineering
Some computational aspects of circumscription
Journal of the ACM (JACM)
On compile-time query optimization in deductive databases by means of static filtering
ACM Transactions on Database Systems (TODS)
Commutativity and its role in the processing of linear recursion
VLDB '89 Proceedings of the 15th international conference on Very large data bases
Direct transitive closure algorithms: design and performance evaluation
ACM Transactions on Database Systems (TODS)
A tool supporting query optimization and program transformation techniques
CSC '90 Proceedings of the 1990 ACM annual conference on Cooperation
Computing transitive closures of multilevel relations
ACM SIGMOD Record
ACM SIGACT News
INC: a language for incremental computations
ACM Transactions on Programming Languages and Systems (TOPLAS)
Towards an algebraic theory of recursion
Journal of the ACM (JACM)
Query Optimization for Nontraditional Database Applications
IEEE Transactions on Software Engineering
On Datalog vs. polynomial time (extended abstract)
PODS '91 Proceedings of the tenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
The expressiveness of a family of finite set languages
PODS '91 Proceedings of the tenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Overbound and right-linear queries
PODS '91 Proceedings of the tenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
K: a high-level knowledge base programming language for advanced database applications
SIGMOD '91 Proceedings of the 1991 ACM SIGMOD international conference on Management of data
QBD*: A Graphical Query Language with Recursion
IEEE Transactions on Software Engineering
Converting nested algebra expressions into flat algebra expressions
ACM Transactions on Database Systems (TODS)
Communicating control knowledge to a deductive database system
CSC '92 Proceedings of the 1992 ACM annual conference on Communications
On the equivalence of recursive and nonrecursive datalog programs
PODS '92 Proceedings of the eleventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Datalog expressiveness of chain queries: grammar tools and characterizations
PODS '92 Proceedings of the eleventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
On tree-based techniques for query evaluation
PODS '92 Proceedings of the eleventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Finding nonrecursive envelopes for Datalog predicate
PODS '93 Proceedings of the twelfth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
ACM Transactions on Database Systems (TODS)
Undecidable optimization problems for database logic programs
Journal of the ACM (JACM)
On the expressive power of query languages
ACM Transactions on Information Systems (TOIS)
On completeness of historical relational query languages
ACM Transactions on Database Systems (TODS)
Will I be pretty, will I be rich?: some thoughts on theory vs. practice in systems engineering
PODS '94 Proceedings of the thirteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
PODS '94 Proceedings of the thirteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
On the complexity of equivalence between recursive and nonrecursive Datalog programs
PODS '94 Proceedings of the thirteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
PODS '94 Proceedings of the thirteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Towards a theory of spatial database queries (extended abstract)
PODS '94 Proceedings of the thirteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Finitely representable databases (extended abstract)
PODS '94 Proceedings of the thirteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Declarative updates of relational databases
ACM Transactions on Database Systems (TODS)
Combinatorial games in database theory
PODS '95 Proceedings of the fourteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Semantics of query languages for network databases
ACM Transactions on Database Systems (TODS)
Applying an update method to a set of receivers (extended abstract)
PODS '95 Proceedings of the fourteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
ACM Transactions on Database Systems (TODS)
Perspectives on database theory
ACM SIGACT News
Relational expressive power of constraint query languages
PODS '96 Proceedings of the fifteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
On genericity and parametricity (extended abstract)
PODS '96 Proceedings of the fifteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Fixpoint logics, relational machines, and computational complexity
Journal of the ACM (JACM)
On the completeness of object-creating database transformation languages
Journal of the ACM (JACM)
Relational expressive power of constraint query languages
Journal of the ACM (JACM)
On the expressive power of datalog: tools and a case study
PODS '90 Proceedings of the ninth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Semigroup techniques in recursive query optimization
PODS '90 Proceedings of the ninth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
The expressive powers of the logic programming semantics (extended abstract)
PODS '90 Proceedings of the ninth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Graph-theoretic methods in database theory
PODS '90 Proceedings of the ninth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
GraphLog: a visual formalism for real life recursion
PODS '90 Proceedings of the ninth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Inherent complexity of recursive queries
PODS '99 Proceedings of the eighteenth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Proceedings of the seventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Possibilities and limitations of using flat operators in nested algebra expressions
Proceedings of the seventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
On the expressive power of database queries with intermediate types
Proceedings of the seventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Proceedings of the seventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Procedural and declarative database update languages
Proceedings of the seventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
A generalized transitive closure for relational queries
Proceedings of the seventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Decidability and undecidability results for boundedness of linear recursive queries
Proceedings of the seventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Optimization of extended database query languages
SIGMOD '85 Proceedings of the 1985 ACM SIGMOD international conference on Management of data
Theseus—a programming language for relational databeses
ACM Transactions on Database Systems (TODS)
Some relational query language design issues and the language MQL
CSC '86 Proceedings of the 1986 ACM fourteenth annual conference on Computer science
Optimization of relational algebra expressions containing recursion operators
CSC '91 Proceedings of the 19th annual conference on Computer Science
PODS '00 Proceedings of the nineteenth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Logic and Databases: A Deductive Approach
ACM Computing Surveys (CSUR)
A Formal System for Reasoning about Programs Accessing a Relational Database
ACM Transactions on Programming Languages and Systems (TOPLAS)
Applying an update method to a set of receivers
ACM Transactions on Database Systems (TODS)
Deciding first-order properties of locally tree-decomposable structures
Journal of the ACM (JACM)
On the computation of relational view complements
Proceedings of the twenty-first ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Programming primitives for database languages
POPL '81 Proceedings of the 8th ACM SIGPLAN-SIGACT symposium on Principles of programming languages
Program schemes, arrays, Lindström quantifiers and zero-one laws
Theoretical Computer Science
On the expressive power of query languages for relational databases
POPL '82 Proceedings of the 9th ACM SIGPLAN-SIGACT symposium on Principles of programming languages
Incorporating computed relations in relational databases
SIGMOD '81 Proceedings of the 1981 ACM SIGMOD international conference on Management of data
Relative information capacity of simple relational database schemata
PODS '84 Proceedings of the 3rd ACM SIGACT-SIGMOD symposium on Principles of database systems
An enhanced inference mechanism for generating relational algebra queries
PODS '84 Proceedings of the 3rd ACM SIGACT-SIGMOD symposium on Principles of database systems
On the complexity and axiomatizability of consistent database states
PODS '84 Proceedings of the 3rd ACM SIGACT-SIGMOD symposium on Principles of database systems
Horn clauses and the fixpoint query hierarchy
PODS '82 Proceedings of the 1st ACM SIGACT-SIGMOD symposium on Principles of database systems
The format model: a theory of database organization
PODS '82 Proceedings of the 1st ACM SIGACT-SIGMOD symposium on Principles of database systems
Deterministic FOIES are strictly weaker
Annals of Mathematics and Artificial Intelligence
Annals of Mathematics and Artificial Intelligence
The power of languages for the manipulation of complex values
The VLDB Journal — The International Journal on Very Large Data Bases
What You Always Wanted to Know About Datalog (And Never Dared to Ask)
IEEE Transactions on Knowledge and Data Engineering
IEEE Transactions on Knowledge and Data Engineering
Moving Selections into Linear Least Fixpoint Queries
IEEE Transactions on Knowledge and Data Engineering
IEEE Transactions on Knowledge and Data Engineering
Extensions to Query Languages for Graph Traversal Problems
IEEE Transactions on Knowledge and Data Engineering
Extending SQL with General Transitive Closure and Extreme Value Selections
IEEE Transactions on Knowledge and Data Engineering
IEEE Transactions on Knowledge and Data Engineering
First-Order Logic Characterization of Program Properties
IEEE Transactions on Knowledge and Data Engineering
Efficient Query Processing for a Subset of Linear Recursive Binary Rules
IEEE Transactions on Knowledge and Data Engineering
Evaluation of Recursive Queries with Extended Rules in Deductive Databases
IEEE Transactions on Knowledge and Data Engineering
G-Log: A Graph-Based Query Language
IEEE Transactions on Knowledge and Data Engineering
Default Logic as a Query Language
IEEE Transactions on Knowledge and Data Engineering
RQL: A Recursive Query Language
IEEE Transactions on Knowledge and Data Engineering
Extending SQL with Generalized Transitive Closure
IEEE Transactions on Knowledge and Data Engineering
IEEE Transactions on Knowledge and Data Engineering
ICDT '01 Proceedings of the 8th International Conference on Database Theory
An Example of Knowledge-Based Query Processing in a CAD/CAM DBMS
VLDB '84 Proceedings of the 10th International Conference on Very Large Data Bases
Translation and Optimization of Logic Queries: The Algebraic Approach
VLDB '86 Proceedings of the 12th International Conference on Very Large Data Bases
On the Computation of the Transitive Closure of Relational Operators
VLDB '86 Proceedings of the 12th International Conference on Very Large Data Bases
VLDB '87 Proceedings of the 13th International Conference on Very Large Data Bases
Query Optimization by Stored Queries
VLDB '87 Proceedings of the 13th International Conference on Very Large Data Bases
Fixed-point semantics and the representation of algorithms on large data
VLDB '88 Proceedings of the 14th International Conference on Very Large Data Bases
Deciding First-Order Properties of Locally Tree-Decomposalbe Graphs
ICAL '99 Proceedings of the 26th International Colloquium on Automata, Languages and Programming
Logic as a Query Language: From Frege to XML
STACS '03 Proceedings of the 20th Annual Symposium on Theoretical Aspects of Computer Science
Generalized Quantifiers in Logic Programs
ESSLLI '97 Revised Lectures from the 9th European Summer School on Logic, Language, and Information: Generalized Quantifiers and Computation
Generalized Quantifiers, an Introduction
ESSLLI '97 Revised Lectures from the 9th European Summer School on Logic, Language, and Information: Generalized Quantifiers and Computation
On the Expressive Power of OCL
FM '99 Proceedings of the Wold Congress on Formal Methods in the Development of Computing Systems-Volume I - Volume I
Program Schemes, Arrays, Lindström Quantifiers and Zero-One Laws
CSL '99 Proceedings of the 13th International Workshop and 8th Annual Conference of the EACSL on Computer Science Logic
Applications of Alfred Tarski's Ideas in Database Theory
CSL '01 Proceedings of the 15th International Workshop on Computer Science Logic
On the computation of relational view complements
ACM Transactions on Database Systems (TODS)
Theoretical Computer Science - Database theory
On the expressive power of variable-confined logics
LICS '96 Proceedings of the 11th Annual IEEE Symposium on Logic in Computer Science
On the Structure of Queries in Constraint Query Languages
LICS '96 Proceedings of the 11th Annual IEEE Symposium on Logic in Computer Science
The complexity of relational query languages (Extended Abstract)
STOC '82 Proceedings of the fourteenth annual ACM symposium on Theory of computing
Relational queries computable in polynomial time (Extended Abstract)
STOC '82 Proceedings of the fourteenth annual ACM symposium on Theory of computing
PEIRCE: A relational DBMS for small systems
SIGSMALL '81 Proceedings of the 1981 ACM SIGSMALL symposium on Small systems and SIGMOD workshop on Small database systems
Computable queries for relational data bases (Preliminary Report)
STOC '79 Proceedings of the eleventh annual ACM symposium on Theory of computing
A practical functional programming system for databases
FPCA '81 Proceedings of the 1981 conference on Functional programming languages and computer architecture
Relations and attributes: A symbiotic basis for editing environments
SLIPE '85 Proceedings of the ACM SIGPLAN 85 symposium on Language issues in programming environments
Languages which capture complexity classes
STOC '83 Proceedings of the fifteenth annual ACM symposium on Theory of computing
Guarded Quantification in Least Fixed Point Logic
Journal of Logic, Language and Information
On the computation of approximations of database queries
ADC '04 Proceedings of the 15th Australasian database conference - Volume 27
Efficient Relational Calculation for Software Analysis
IEEE Transactions on Software Engineering
An overview of cantor: a new system for data analysis
SSDBM'83 Proceedings of the 2nd international workshop on Proceedings of the Second International Workshop on Statistical Database Management
GRASP: a graphical system for statistical databases
SSDBM'1990 Proceedings of the 5th international conference on Statistical and Scientific Database Management
Relational programming with CrocoPat
Proceedings of the 28th international conference on Software engineering
One-to-many data transformations through data mappers
Data & Knowledge Engineering
Fundamental and secondary issues in the design of non-procedural relational languages
VLDB '79 Proceedings of the fifth international conference on Very Large Data Bases - Volume 5
G-WHIZ, a visual interface for the functional model with recursion
VLDB '85 Proceedings of the 11th international conference on Very Large Data Bases - Volume 11
The representation and deductive retrieval of complex objects
VLDB '85 Proceedings of the 11th international conference on Very Large Data Bases - Volume 11
Impacts of logic and databases (invited paper)
VLDB '81 Proceedings of the seventh international conference on Very Large Data Bases - Volume 7
On retrieval from a small version of a large data base
VLDB '80 Proceedings of the sixth international conference on Very Large Data Bases - Volume 6
On the Descriptive Complexity of Linear Algebra
WoLLIC '08 Proceedings of the 15th international workshop on Logic, Language, Information and Computation
One Useful Logic That Defines Its Own Truth
MFCS '08 Proceedings of the 33rd international symposium on Mathematical Foundations of Computer Science
Towards a theory of search queries
Proceedings of the 12th International Conference on Database Theory
Extending SPARQL with regular expression patterns (for querying RDF)
Web Semantics: Science, Services and Agents on the World Wide Web
Program Schemes, Queues, the Recursive Spectrum and Zero-one Laws
Fundamenta Informaticae - Machines, Computations and Universality, Part II
On Importing Knowledge from Ontologies.
Modular Ontologies
Decidability of $\mathcal{SHI}$ with Transitive Closure of Roles
ESWC 2009 Heraklion Proceedings of the 6th European Semantic Web Conference on The Semantic Web: Research and Applications
Query translation from XPath to SQL in the presence of recursive DTDs
The VLDB Journal — The International Journal on Very Large Data Bases
Synthesizing least fixed point queries into non-recursive iterative programs
IJCAI'83 Proceedings of the Eighth international joint conference on Artificial intelligence - Volume 1
Augmenting concept languages by transitive closure of roles: an alternative to terminological cycles
IJCAI'91 Proceedings of the 12th international joint conference on Artificial intelligence - Volume 1
Query by diagram: A fully visual query system
Journal of Visual Languages and Computing
Towards a theory of search queries
ACM Transactions on Database Systems (TODS)
Terminological cycles in KL-ONE-based knowledge representation languages
AAAI'90 Proceedings of the eighth National conference on Artificial intelligence - Volume 1
Automated generation of itineraries in recommender systems for tourism
ICWE'10 Proceedings of the 10th international conference on Current trends in web engineering
Intelligent author identification
ER'10 Proceedings of the 2010 international conference on Advances in conceptual modeling: applications and challenges
CIEL: a universal execution engine for distributed data-flow computing
Proceedings of the 8th USENIX conference on Networked systems design and implementation
Fields of logic and computation
Fixed-point definability and polynomial time on chordal graphs and line graphs
Fields of logic and computation
Data mapper: an operator for expressing one-to-many data transformations
DaWaK'05 Proceedings of the 7th international conference on Data Warehousing and Knowledge Discovery
FoIKS'12 Proceedings of the 7th international conference on Foundations of Information and Knowledge Systems
On the decidability and complexity of identity knowledge representation
DASFAA'12 Proceedings of the 17th international conference on Database Systems for Advanced Applications - Volume Part I
A data flow language for hybrid query and programming languages
FLOPS'12 Proceedings of the 11th international conference on Functional and Logic Programming
Program Schemes, Queues, the Recursive Spectrum and Zero-one Laws
Fundamenta Informaticae - Machines, Computations and Universality, Part II
A UNIVERSAL MODEL FOR NON-PROCEDURAL DATABASE LANGUAGES
Fundamenta Informaticae
CATEGORISATION OF COMPUTABLE DATABASE QUERIES
Fundamenta Informaticae
On the expressive power of update primitives
Proceedings of the 32nd symposium on Principles of database systems
Editorial: Data migration: A theoretical perspective
Data & Knowledge Engineering
| Hi-index | 0.03 |
We consider the question of how powerful a relational query language should be and state two principles that we feel any query language should satisfy. We show that although relational algebra and relational calculus satisfy these principles, there are certain queries involving least fixed points that cannot be expressed by these languages, yet that also satisfy the principles. We then consider various extensions of relational algebra to enable it to answer such queries. Finally, we discuss our extensions to relational algebra in terms of a new programming language oriented model for queries.