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Microblogs such as Twitter provide a valuable stream of diverse user-generated data. While the data extracted from Twitter is generally timely and accurate, the process by which developers extract structured data from the tweet stream is ad-hoc and requires reimplementation of common data manipulation primitives. In this paper, we present two systems for querying and extracting structure from Twitter-embedded data. The first, TweeQL, provides a streaming SQL-like interface to the Twitter API, making common tweet processing tasks simpler. The second, TwitInfo, shows how end-users can interact with and understand aggregated data from the tweet stream, in addition to showcasing the power of the TweeQL language. Together these systems show the richness of content that can be extracted from Twitter.

In this paper we describe the fundamental components of a database management system for the definition, storage, manipulation and query of aggregate data, i.e. data which are obtained by applying statistical aggregations and statistical analysis functions over raw data. In particular, the attention has been focused on: (1) a data structure for the efficient storage and manipulation of aggregate data, called ADaS; (2) the graphical structures of the aggregate data model ADAMO for a more user-friendly definition and query of aggregate data; (3) a graphical user interface which enables a straightforward specification of the ADAMO structures; (4) a textual declarative query language to retrieve data from the aggregate database, called ADQUEL.

HYPERQUERY is a hypertext query language for object-oriented pictorial database systems. First, we discuss object calculus based on term rewriting. Then, example queries are used to illustrate language facilities. This query language has been designed with a flavor similar to QBE as the highly nonprocedural and conversational language for object-oriented pictorial database management system OISDBS.

We describe the design and implementation of the Glue-Nail database system. The Nail language is a purely declarative query language; Glue is a procedural language used for non-query activities. The two languages combined are sufficient to write a complete application. Nail and Glue code both compile into the target language IGlue. The Nail compiler uses variants of the magic sets algorithm, and supports well-founded models. Static optimization is performed by the Glue compiler using techniques that include peephole methods and data flow analysis. The IGlue code is executed by the IGlue interpreter, which features a run-time adaptive optimizer. The three optimizers each deal with separate optimization domains, and experiments indicate that an effective synergism is achieved. The Glue-Nail system is largely complete and has been tested using a suite of representative applications.

The incorporation of a knowledge of time within database systems allows for temporally related information to be modelled more naturally and consistently. Adding this support to the metadatabase further enhances its semantic capability and allows elaborate interrogation of data. This paper presents SQL/SE, an SQL extension capable of handling schema evolution in relational database systems.

In this paper we introduce DOODLE, a new visual and declarative language for object-oriented databases. The main principle behind the language is that it is possible to display and query the database with arbitrary pictures . We allow the user to tailor the display of the data to suit the application at hand or her preferences. We want the user-defined visualizations to be stored in the database, and the language to express all kinds of visual manipulations. For extendibility reasons, the language is object-oriented. The semantics of the language is given by a well-known deductive query language for object-oriented databases. We hope that the formal basis of our language will contribute to the theoretical study of database visualizations and visual query languages, a subject that we believe is of great interest, but largely left unexplored.

This paper proposes a method for handling inapplicable and unknown missing data. The method is based on: (1) storing default values (instead of null values) in place of missing data, (2) storing truth values that describe the logical status of the default values in corresponding fields of corresponding tables. Four valued logic is used so that the logical status of the default data values can be described as, not just true or false, but also as inapplicable or unknown. This method, in contrast to the “hidden byte” approach, has two important advantages: (1) Because the logical status of all data is represented explicitly in tables, all 4-valued operations can be handled via a 2-valued data manipulation language, such as SQL. Language extensions for handling missing data (e.g., “IS NULL”) are not necessary. (2) Because data fields always contain a default value (as opposed to a null value or mark), it is possible to do arithmetic across missing data and to interpret the logical status of the result by means of logical operations on the corresponding stored truth values.

We define the independence-reducibility based on a modification of key dependencies, which has better computational properties and is more practically useful than the original one based on key dependencies. Using this modification as a tool, we design BCNF databases that are highly desirable with respect to updates and/or query answering. In particular, given a set U of attributes and a set F of functional dependencies over U, we characterize when F can be embedded in a database scheme over U that is independent and is BCNF with respect to F, a polynomial time algorithm that tests this characterization and produces such a database scheme whenever possible is presented. The produced database scheme contains the fewest possible number of relation schemes. Then we show that designs of embedding constant-time-maintainable BCNF schemes and of embedding independence-reducible schemes share exactly the same method with the above design. Finally, a simple modification of this method yields a polynomial time algorithm for designing embedding separable BCNF schemes.

SuperSQL is an extension of SQL that allows query results presented in various media for publishing and presentations with simple but sophisticated formatting capabilities. SuperSQL query can generate various kinds of materials, for example, a LaTeX source file to publish query results in a nested table, HTML or Java source files to present the result on WWW browsers, and other media including MS-Excel worksheet, Tcl/Tk, O2C, etc. O2C is a data manipulation language of O2 and thus useful to migrate data in a relational database to an object oriented database. SuperSQL is meant to provide a theoretical and practical foundation for 4GL-type applications such as report writers and DB/WWW coordinators. In this demonstration, we show how TFE reorganize the query results into various media in a universal way, first by grouping tuples according to an arbitrary tree structured schema, and by translating them with the constructors available in the target media.

ODE is a database system and environment based on the object paradigm. It offers one integrated data model for both database and general purpose manipulation. The database is defined, queried and manipulated in the database programming language O++ which is based on C++. O++ borrows and extends the object definition facility of C++, called the class. Classes support data encapsulation and multiple inheritance. We provide facilities for creating persistent and versioned objects, defining sets, and iterating over sets and clusters of persistent objects. We also provide facilities to associate constraints and triggers with objects. This paper presents the linguistic facilities provided in O++ and the data model it supports.

The ANS Database Committee (X3H2) is currently at work on a proposed standard relational database language (RDL), and has adopted as a basis for that activity a definition of the "structured query language" SQL from IBM [10]. Moreover, numerous hardware and software vendors (in addition to IBM) have already released or at least announced products that are based to a greater or lesser extent on the SQL language as defined by IBM. There can thus be little doubt that the importance of that language will increase significantly over the next few years. Yet the SQL language is very far from perfect. The purpose of this paper is to present a critical analysis of the language's major shortcomings, in the hope that it may be possible to remedy some of the deficiencies before their influence becomes too all-pervasive. The paper's standpoint is primarily that of formal computer languages in general, rather than that of database languages specifically.

ROSE is an experimental database system for CAD/CAM applications that organizes a database into entries and relationships. The data model of ROSE is an extension of the relational model and the data manipulation language is an extension of the relational algebra. Internally, ROSE is organized so that it can use operating system services to implement database system services. In this paper we describe five optimizations that have helped to make ROSE a fast database system for CAD/CAM.

An extension of the database language SQL is described which introduces several new concepts into the language that are standard in the relational model, but surprisingly not present in available SQL-based systems such as SQL/DS and DB2.

Many new database applications require computational and data modelling power simply not present in conventional database management systems. Developers are forced to design complex encodings of complex data into a limited set of database types, and to embed DML commands into a host programming language, a notoriously tricky and error-prone enterprise. In this paper, we describe the design and implementation of GESTALT, a system and methodology for organizing and interfacing to multiple heterogeneous, existing database systems. Application programs are written in a supported programming language (currently C and Lisp) using high-level data and control abstractions native to the language. The system is flexible in that the underlying database systems can easily be replaced/upgraded/augmented without affecting existing application programs. We also describe our experience with the system: GESTALT has been in daily operational use at MIT for over a year, supporting an information system for CAF, a research facility for the automation of semiconductor fabrication.

Machiavelli is a polymorphically typed programming language in the spirit of ML, but supports an extended method of type inferencing that makes its polymorphism more general and appropriate for database applications. In particular, a function that selects a field ƒ of a records is polymorphic in the sense that it can be applied to any record which contains a field ƒ with the appropriate type. When combined with a set data type and database operations including join and projection, this provides a natural medium for relational database programming. Moreover, by implementing database objects as reference types and generating the appropriate views — sets of structures with “identity” — we can achieve a degree of static type checking for object-oriented databases.

This paper summarizes discussions of a panel on "Type Specifications and Databases" at VLDB in Mexico City. Panel members are listed at the end of the paper.Significant advances have been achieved in software engineering and programming language research in the development of specification techniques. There are important consequences for design, redesign, precision, and analysis of software. The importance of this work to database applications, and indeed data models and data languages, is now becoming apparent. However, specific database issues (e.g., constraints, complex data relationships, shared data, data independence) alter the specification problem as encountered in programming languages. The summary emphasizes the importance of (precise) specification in the database context and relates recent results in both programming languages and databases. It also lists outstanding theoretical problems and the relationship of advances in specification research to the development of semantic data models and high level languages for databases.

The question of defining data types in a database language is examined. In order to illustrate the general ideas and make them more concrete, the specific case of adding support for dates and times to the database language SQL is considered in detail.

Adaplex is an integrated language for programming database applications. It results from the embedding of the database sublanguage DAPLEX in the general purpose programming language Ada. This paper provides an overview of the DDM: a distributed database manager (DDM) that supports the use of Adaplex as an interface language. The important technical innovations we have incorporated in the design of this system include:1. An advanced data model that captures more application semantics than conventional data models.2. Support for flexible data distribution options that improve locality of reference and efficiency of query processing.3. Extensive query optimization that combines compile time access path optimization with run time site selection.4. Efficient transaction management that reduces transaction conflicts and improves the resiliency of replicated data.5. Robust, incremental recovery management that provides for automatic recovery from certain "catastrophic" failure conditions.