AllegroGraph

AllegroGraph is a database and application framework for building Semantic Web applications. It can store data and meta-data as triples, query these triples through various query APIs like SPARQL and Prolog, and apply RDFS++ reasoning with its built-in reasoner. It's a high performance, persistent RDF store to support Social Network Analysis, Geospatial capabilities, Temporal reasoning, etc.

History

The first version of AllegroGraph was made available at the end of 2004 by Franz Inc.. It is an ongoing project with the latest stable release 6.3.0 in October 24, 2017. The idea behind developing AllegroGraph as a graph database was to store your relationships as RDF triples, a standard format for Linked Data.

Query Interface

Custom API

Users can query AllegroGraph with SPARQL, RDFS++ Reasoning or Prolog. SPARQL is the query language of choice for modern triple stores. AllegroGraph's RDFS++ reasoning supports all the RDFS predicates and some of OWL's. Prolog is an alternative query mechanism for AllegroGraph. With Prolog, you can specify queries declaratively.

Views

Not Supported

Current graph databases such as Neo4J, AllegroGraph, and InfiniteGraph do not provide a concept for view definition and maintenance.

Concurrency Control

Not Supported

No triple locking is performed by AllegroGraph. It uses snapshot isolation and it is possible that a triple that is being read in a transaction could be deleted in a concurrent transaction. It cannot guarantee write concurrency

Logging

Logical Logging

When the commit operation of AllegroGraph returns, the database server will have written the updates made by the transaction to the transaction log and waited for the log I/O operation to finish. Transaction log files record all committed database changes (triple additions and deletions), along with some other information.

Storage Model

Custom

It shores data as the Resource Description Framework (RDF), which breaks knowledge into assertions of subject predicate object (e.g. Andy Type Human ). These assertions are called triples. AllegroGraph doesn't restrict the contents of its triples to pure RDF. In fact, we can represent any graph data-structure by treating its nodes as subjects and objects, its edges as predicates and creating a triple for every edge.

Isolation Levels

Snapshot Isolation

Every transaction sees a snapshot of the persistent database state as of the time when the transaction is started. During the transaction, it can change the persistent state without affecting the snapshot of others. When finishes, any updates made by concurrent transactions are visible.

Stored Procedures

Supported

Users can use Lisp or JavaScript to define stored procedures.

Data Model

Graph

AllegroGraph is a closed source triplestore which is designed to store RDF triples, a standard format for Linked Data.

System Architecture

Shared-Nothing

AllegroGraph follows shared-nothing model, adopts federation mechanism and flexible triple store architecture combine to make it easy to connect multiple stores together and treat them as one. When a user creates an AllegroGraph federated repository, a virtual index of the constituent stores is created and maintained in the client session to facilitate intelligent query processing and maximum performance.

Query Compilation

Not Supported

AllegroGraph Logo
Website

https://franz.com/agraph/allegrograph

Tech Docs

https://franz.com/agraph/support/documentation/current/index.html

Developer

Franz, Inc.

Country of Origin

US

Start Year

2004

Project Type

Commercial

Written in

Lisp

Supported languages

C#, Clojure, Java, Lisp, Perl, Python, Ruby, Scala

Operating Systems

Linux, OS X, Windows

Licenses

Proprietary