Sunday, June 17, 2012

JSON Storage in HyperGraphDB

JSON ( came about as a convenient, better-than-XML data format that one could directly work from in JavaScript.  About a year ago, I got a bit disappointed by the JSON libraries out there. JSON is so simple, yet all of them so complicated, so verbose. Most of it comes from the culture of strong typing in Java and from the presumed use of JSON on the server as an intermediate representation to be mapped to Java beans, where the application domain is usually modeled. But JSON is powerful enough on its own if you are willing to trade off type safety for flexibility. So I wrote mJson (for "minimal" Json), a single source file library for working with JSON from Java. For a description see the blog posts:

Using this library, I've been able to avoid creating the usual plethora of Java classes to work with my domain in several applications. Coding with it is pretty neat. One can pretty much view JSON as a general minimalistic, highly flexible modeling tool, a bit like s-expressions or any general enough abstract data structure (another example are first-order logic terms). 

Now, there's a persistence layer for those JSON entities based on HyperGraphDB. Unlike "document-oriented" databases, the representation in HyperGraphDB is really graph-like with all the expected consequences. It is described in the HyperGraphDB Json Wiki Page, pretty stable, convenient and fun to work with. 

If time permits, I will write a few posts in the form of a tutorial to show how to quickly build database backed JSON REST services with mJson and HyperGraphDB. If you have a suggestion of an application domain to cover, please share it in a comment!

In the meantime, I invite you to give it a try! 



Monday, June 11, 2012

HyperGraphDB 1.2 Beta now available

Kobrix Software is pleased to announce the release of HyperGraphDB version 1.2.

HyperGraphDB is a general purpose, free open-source data storage mechanism. Geared toward modern applications with complex and evolving domain models, it is suitable for semantic web, artificial intelligence, social networking or regular object-oriented business applications.

This release contains numerous bug fixes and improvements over the previous 1.1 release. A fairly complete list of changes can be found at the Changes for HyperGraphDB, Release 1.2 wiki page.

  1. Introduction of a new HyperNode interface together with several implementations, including subgraphs and access to remote database peers. The ideas behind are documented in the blog post HyperNodes Are Contexts.
  2. Introduction of a new interface HGTypeSchema and generalized mappings between arbitrary URIs and HyperGraphDB types.
  3. Implementation of storage based on the BerkeleyDB Java Edition (many thanks to Alain Picard and Sebastian Graf!). This version of BerkeleyDB doesn't require native libraries, which makes it easier to deploy and, in addition, performs better for smaller datasets (under 2-3 million atoms).
  4. Implementation of parametarized pre-compiled queries for improved query performance. This is documented in the Variables in HyperGraphDB Queries blog post.

HyperGraphDB is a Java based product built on top of the Berkeley DB storage library.

Key Features of HyperGraphDB include:
  • Powerful data modeling and knowledge representation.
  • Graph-oriented storage.
  • N-ary, higher order relationships (edges) between graph nodes.
  • Graph traversals and relational-style queries.
  • Customizable indexing.
  • Customizable storage management.
  • Extensible, dynamic DB schema through custom typing.
  • Out of the box Java OO database.
  • Fully transactional and multi-threaded, MVCC/STM.
  • P2P framework for data distribution.
In addition, the project includes several practical domain specific components for semantic web, reasoning and natural language processing. For more information, documentation and downloads, please visit the HyperGraphDB Home Page.