SC22/WG20 N1014 From kuester@saphor.de Mon Feb 10 18:18:07 2003 From: Marc Wilhelm Kuester Subject: Sorting text X-Keywords: Hello! Here the announce discussion document on internationalized sorting. It's for distibution tomorrow. Thanks and until tomorrow! Marc -- ************************* Marc Wilhelm Küster Saphor GmbH Fronländer 22 D-72072 Tübingen Tel.: (+49) / (0)7472 / 949 100 Fax: (+49) / (0)7472 / 949 114 E-Mail: kuester@saphor.net Web: http://www.saphor.net -------------------------------------------------------------- A few ideas on sorting Marc Wilhelm Küster A few loose terms: sorting: a well-defined arrangement of two sortables using the algorithm that is specified later on sortable: a sequence of one or more orderables. The type of a sortable is defined by the sequence of types of the orderables orderable: a unit which has a well-defined ordering with regards to other units of the same type ordering: the arrangement of two units of the same type into a well-defined sequence Note: A special case of ordering is string ordering Note: Two units can be considered to be of the same type if their respective values have a comparison function that puts them into a well-defined greater-than relationship. Note: In reality, sortables will be read from some datasource. This datasource can be a structured file (e.g. an XML-based file format), a relational database, an object-oriented database or something else that can deliver structured data. Sorting vs. ordering In usual English parlance sorting and ordering are roughly equivalent terms. For the purpose of this text they have different meanings, however: Ordering is the arrangement of basic units such as strings or numbers into a well-defined order whereas sorting is the arrangement of sequences of orderable units into a well-defined order. An example for this distinction is the ordering of simple strings such as abacus and abc in contrast to the sorting of phone book entries where each entry consists of (e.g.) a family name, one or more first names, a street name, a house number and finally a telephone number. The rules for sorting are culturally sensitive as well as potentially subject to personal preferences. It is likewise dependent on the type of sortable at hand and the field of application. A document on this issue must define a sample syntax for a unambiguous definition of the sorting rules within this framework. The multikey algorithm Any sorting problem can be solved by a the following algorithm, usually known as the multikey algorithm. Two sortables can be compared by: 1. Taking the first orderable from both sortables 1a. If using "word-by-word ordering" for strings, split the orderable along the desired split criterion (usually whitespace) and follow this algorithm for each of the resulting parts 2. Apply any required preprocessing to each of the two orderables 3. Comparing the two resulting units. If they have a unique ordering, than this is the sequence of the two sortables Repeat this algorithm for all orderables until a unique sequence could be found. If no sequence can be found, the sortables are considered equivalent. Preprocessing Preprocessing of orderables is for some types of orderables a necessity in most fields of application. For strings, preprocessing can be seen conceptionally as the application of UNIX-style regular expressions to a string (though in reality, it would rarely be defined in this manner). Preprocessing is culturally sensitive. Rules for preprocessing are traditionally defined in national sorting standards such as NF Z 44-001 for France, DIN 5007-2 for Germany and (to a lesser extend) ANSI/NISO Z39.75 for the US. A sample syntax must allow for the definition of (potentially complex) preprocessing rules. Ordering Each of the orderables needs a well-defined comparison method. For some orderables such as natural numbers the ordering will rarely be disputed and could hardly be considered to be culturally sensitive. For other units such as strings the comparison method is highly dependend on the culture in question (cf. ISO/IEC 14651). For yet other types such as complex numbers there is no single accepted comparison method. Yet other types may have monetary or other unit signs attached to them which will directly influence the comparison (e.g. 1 cm compared to 1 inch or USD 1 compared to EUR 1). A sample syntax must allow for the definition of ordering rules for different types of orderables and potentially for different rules for orderables of the same type when they appear in different positions of the same sortable. Syntax The TR must provide a sample syntax for the customized specification of an internationalized sorting algorithm much in the same vein that ISO/IEC 14651 provides a sample syntax for defining culturally adapted ordering specifications. This sample syntax will be XML based (and thus also be ISO 8879 conformant). It should be able to drive an application. Preparation of a quality document This paper sketches the basics for an internationalized sorting algorithm. The details for the configuration and implementation of such an algorithm are still open. In order to get a quality document, an open-source reference sample application should be developed in sync with the progress of this document. Sample application The reference application should use object-oriented techniques consistently to minimize the porting effort between OO-languages. C# (ISO/IEC 23270) is suggested as a suitable language for the reference implementation.