A brief introduction to the Callimachus Project, an Open Source software project to make the creation of Semantic Web applications easy for Web authors.

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2. Καλλίμαχος of Cyrene
c. 305–c. 240 BCE
• Father of Bibliography (The Pinakes)
at the great Library at Alexandria
• Could not categorize his own work
in Aristotle’s hierarchical system
“Mega biblion, mega kakon”
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“Many writings equals many worries”
Pinakes: Tables of those who were eminent in every branch of learning, and what they wrote,
in 120 volumes
Callimachus’ Quandary was that he could not categorize his own works in Aristotle’s
hierarchy.

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Semantic Web applications have been hampered by our pre-conceived notions of software
architecture. It has taken us ten years to build a full architecture.

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Like Aristotle’s hierarchy, we have thumb rules and presumptions in our software
architectures. The 3-tier architecture is very useful, but most people equate the data layer
with hierarchical or pseudo-hierarchical data stores like relational databases and file systems.

5. 1. Object-RDF mapping
2. RDF
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We try to address Callimachus’ Quandary by removing limitations implicit in the n-tier
architecture. Objects are exposed to the user interface so we can keep using existing means
of creating UIs, but those limitations are not serialized.

6. The painter... does not fit the paints to the world.
He fits himself to the paint.
-- Paul Klee
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Older attempts at creating RDF editors suffered from being too close to triples. Other
products make an orthogonal mistake by storing objects based on RDF, thus limiting
arbitrary relationships in the data. Callimachus tries to avoid both problems by presenting
objects to the user while storing RDF natively.

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In our opinion, Semantic Web apps should look like arbitrary Web pages.

9. RDF Store
Web server
HTTP GET Class
Resource
request
Viewable
RDF response
SPARQL query
XML
template apply.xsl
HTTP
response HTML
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10. Demo Time!
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11. Graph Pattern Queries
• Every triple is also a triple pattern
• Any graph can be used within a SPARQL ASK
query
• Basic triple patterns are triples with variables
• Variables can be stored in triples as URI within a
particular namespace
• Many CONSTRUCT and SELECT queries can be
represented using triples with variables
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12. RDFa Pattern Queries
• RDFa is parsed into RDF
• Variables are identified by URI namespace for
conversion into basic triple patterns
• Nested tags use OPTIONAL joins to maximise
matches
• RDFa file is used to construct RDFa result of
matching triples
• Callimachus project contains an implementation of
the above
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13. UI Templates
• Use external BASE to enable query reuse against
different subjects
• Template for every resource type and activity
• Activities include:
• View resource
• Review resource
• Edit resource
• Copy resource
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14. RDFa Changesets
• JavaScript RDFa library for parsing and identifying
differences on client side
• JavaScript library for RDFa aware DOM
manipulation
• POST changes back to server as RDF or SPARQL
Update
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15. When to use SPARQL
• RDFa does not include
• Join types (inner, left, cross, union)
• FILTER
• ORDER BY
• LIMIT, OFFSET
• GRAPH support
• For these constructs use SPARQL results with XSLT
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16. Managing Resources with RDFa
• Identify or create a resource vocabulary
• Create resource templates for every resource type
and activity in RDFa
• Create search interface with SPARQL and XSLT
• Semantic Web applications made easy!
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17. For More Information
• Contact
• James Leigh <james@leighnet.ca>
• David Wood <david@3roundstones.com>
• Get involved at
• http://callimachusproject.org/
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