CQL stands for Class Query Language ; it is an extension of SQL towards the classes of mathematical logic. But unlike SQL, CQL is not limited to relational databases (RDBMS), it is rather intended to manage and query object-oriented databases (OODBMS)and other Library Management Systems (LMS).
The philosophy behind is simple: a declarative and neutral query language for class hierarchies. As a result, CQL is very well suited for use with PLIB driven LMS for both queries and data modeling. However the scope of the language is not limited to PLIB but is applicable to a wide-range of object-oriented class libraries.
Among its main features, CQL allows the use of set-theoretic boolean operations between classes that together form an acyclic graph structure and it embeds many datatypes comonly used in data modeling (since its version 2.0, CQL provides a consistent Collection framework). Moreover, meta-data can be queried and manipulated just like basic data, making it easy to browse any hierarchy of classes.
Eventually, besides compatibility with CSV files (Excel format) and STEP files (also called Part21 file format, defined in ISO-10303-21 STEP standard), CQL defines a new XML based file format (Parcelling format) to ease migration and exchanges of data/meta-data between heterogeneous systems, bypassing the problem of multiple character-set encodings.
Documents:
- Class Query Language
and its application to ISO13584 Parts Library Standard
by Yumiko Mizoguchi-Shimogori, Hiroshi Murayama, Noriko Minamino
(ECEC'2002 9th European Concurrent Engineering Conference)
Concurrent Engineering: System integration for profit p128-p135, 2002, SCS
- Modeling Product Ontology with CQL
by Hiroshi Murayama , Olivier Lemarchand and Yumiko Mizoguchi-Shimogori
(10th ISPE International Conference on Concurrent Engineering, July2003, Madeira, Portugal)
Concurrent Engineering: Enhanced Inter Operable Systems, p279-p286, 2003, SCS
CQL Specifications:
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