SQL provides NULL values for attributes which are unknown to the user. There are three meanings of NULL but they are not classified by database engines. Results of SQL queries show different meaning when they are produced by subqueries. This paper explains the meaning of them with suggestions ...
英文: Semantics: examines how meaning is encoded in a language.中文: 语义学:考察的是意义如何在语言中编码。英文: The key definitions of spatio-temporal data modeling are summarized and the requirements of spatio-temporal database community, including temporal semantics, spatial semantics, spatio-...
For example, when we use checkbox, if we do like this: Receive promotional offers? When we use screen reader, it will lose the semantics meaning, it only say: checkbox checked Instead, we want to hear: Receive promotional offers?, checkbox, checked There are two way to do it: 1. label...
It is shown that the navigational structure provided by the object model can be exploited to present joins and nesting constructs contained in an SQL-query. It is also shown that with such a translation, considerable gain in the intuitive meaning of the query can be achieved. When applied to...
Lines 9–13 essentially represent the SQL query given above, and lines 1-6 and 14–17 capture the meaning of the pseudo-RDF. We provide the rule only as an illustration, so readers interested in details of PSOA RuleML are referred to [30]. ...
This sequence of SQL commands preserves the existing value of wsrep_sync_wait and then sets it to at least 1, meaning that SELECTs are subject to causal wait. Once we have issued the SELECT, we restore the previous value of the variable....
Here is the meaning of the replication parameter: 000: no replication 001: replicate once on the same rack 010: replicate once on a different rack, but same data center 100: replicate once on a different data center 200: replicate twice on two different data center 110: replicate once on ...
*+ operators, meaning zero-or-one, zero- or-more and one-or-more respectively. Expressions can be grouped in paren- theses, (), to control order of evaluation. Semantic predicate operators &! match an expression but never consume any of the text. The and-predicate & matches if the ...
4) The model should be designed in a forward-looking manner, anticipating other likely data elements, to minimize the need for future disruptive changes. Examination of the EU RD CDEs revealed that there were, in fact, many inter-dependencies between them – meaning that one CDE could not re...
The OBO format is human friendly, and useful GUI-based tools like OBO-Edit are available for building ontologies in it [13]. We deal with OBO version 1.2, and refer to it as simply OBO in this paper. Semantic Web ontologies The Semantic Web ontologies give well-defined meaning to the co...