Quaestiones Informaticae Vol 5 No 3
http://hdl.handle.net/10500/24190
2020-09-18T18:19:55ZGenerating relations using formal grammars
http://hdl.handle.net/10500/24249
Generating relations using formal grammars
von Solms, S. H.
Grammars generating 2-dimensional arrays have been studied by many people [1, 2, 3, 4). One effort was
Random Context Array Grammars [4], where different types of context conditions placed on the production, were
used to control the generating process.
Relations, as used in relational data bases, can be considered as rectangular arrays, and therefore it should be
possible to generate and manipulate relations using 2-dimensional Grammars.
Simple Relation Grammars generate relations, and can simulate some unary operations like select and
project on these relations.
Extended Relation Grammars also generate relations, but these relations can communicate with each other
within a "Extended Relation Schema (ERS)". Within such an ERS binary operations like union and join can be
simulated.
This paper is a summary of a research project of which certain parts have already been submitted for
publication.
1987-01-01T00:00:00ZPointers as a data type
http://hdl.handle.net/10500/24246
Pointers as a data type
Philips, N.C.K.; Postma, Stef W.
The distinction between an abstract data type and an implementation of a data type is not as
clear as is commonly thought. A hash table can be used to implement the type bag but few of our
colleagues think of a hash table as itself being a data type. Similarly, pointers can be used to give
a linked implementation of the data type list, but few of us seem to think of pointers as
themselves forming a data type. However we shall give an algebraic specification of a pointer
data type which is an abstraction of the representation of pointers in Pascal. The usual linked
structures can then be specified abstractly via mutually recursive type specifications. In addition
we shall describe a uniform method of constructing implementations of data type specifications
via operations on strings.
1987-01-01T00:00:00ZCommon approach to some informational systems
http://hdl.handle.net/10500/24245
Common approach to some informational systems
Orlowska, M.E.
In this paper we consider relationships between a complete system [6], an L-system [3], a stochastic
system [13] and an N-system [8]. We introduce a notion of the induction of one system by another. We prove
the important fact that an N-system is a common generalization of all the systems mentioned above. This fact
is clearly demonstrated using geometric characterization of the set of subcontinua of the internal <0, l>.
1987-01-01T00:00:00ZThree packaging rules for information system design
http://hdl.handle.net/10500/24244
Three packaging rules for information system design
Mende, J.
After identifying the processing functions required in a computer based information system, the designer needs
to combine them into an optimal set of load units. Some "packaging" arrangements yield a better system than
others, depending upon characteristics of the data collected from external sources and the data extracted for external
users. An effective and technically efficient system satisfies three rules.
1. If two user data types are needed at different times, the corresponding extract functions should be
separated in different load units.
2. If source data predates the user data derived from it, the corresponding collect and extract functions
should be separated in different load units.
3. If two source data types are available at different frequencies, one being less frequent than the user
data derived from it, the corresponding collect functions should be separated in different load units.
1987-01-01T00:00:00Z