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© 2008 Thomas Neumann Note: A more recent version of the RDF-3X code is available at http://code.google.com/p/rdf3x/ .
A sample Entity – Relationship diagram using Chen's notation Entity–relationship model ( ER model ) in software engineering is an abstract way to describe a database . This article refers to the techniques proposed in Peter Chen 's 1976 paper. [ 1 ] However, variants of the idea existed previously, [ 2 ] and have been devised subsequently such as supertype and subtype data entities [ 3 ] and commonality relationships.
Overview YAGO2s is a huge semantic knowledge base, derived from Wikipedia WordNet and GeoNames . Currently, YAGO2s has knowledge of more than 10 million entities (like persons, organizations, cities, etc.) and contains more than 120 million facts about these entities.
UML logo Unified Modeling Language ( UML ) is a standardized general-purpose modeling language in the field of object-oriented software engineering . The Unified Modeling Language includes a set of graphic notation techniques to create visual models of object-oriented software-intensive systems.
I found myself reading NoSQL is a Premature Optimization a few minutes ago and threw up in my mouth a little. That article is so far off base that I’m not even sure where to start, so I guess I’ll go in order. In fact, I would argue that starting with NoSQL because you think you might someday have enough traffic and scale to warrant it is a premature optimization, and as such, should be avoided by smaller and even medium sized organizations. You will have plenty of time to switch to NoSQL as and if it becomes helpful. Until that time, NoSQL is an expensive distraction you don’t need.
Database Models: Hierarcical, Network, Relational, Object-Oriented, Semistructured, Associative and Context.Each Column Has a Unique Name Certain fields may be designated as keys, which means that searches for specific values of that field will use indexing to speed them up. Where fields in two different tables take values from the same set, a join operation can be performed to select related records in the two tables by matching values in those fields. Often, but not always, the fields will have the same name in both tables. For example, an "orders" table might contain (customer-ID, product-code) pairs and a "products" table might contain (product-code, price) pairs so to calculate a given customer's bill you would sum the prices of all products ordered by that customer by joining on the product-code fields of the two tables. This can be extended to joining multiple tables on multiple fields. Because these relationships are only specified at retreival time, relational databases are classed as dynamic database management system.
The associative model of data is an alternative data model for database systems. Other data models, such as the relational model and the object data model, are record-based. These models involve encompassing attributes about a thing, such as a car, in a record structure. Such attributes might be registration, colour, make, model, etc.
PyTables is a package for managing hierarchical datasets and designed to efficiently and easily cope with extremely large amounts of data. You can download PyTables and use it for free . You can access documentation , some examples of use and presentations in the HowToUse section. PyTables is built on top of the HDF5 library , using the Python language and the NumPy package. It features an object-oriented interface that, combined with C extensions for the performance-critical parts of the code (generated using Cython ), makes it a fast, yet extremely easy to use tool for interactively browse, process and search very large amounts of data.