Research Seminars
Historic seminars
2001
Wed 25th April Guido Bugmann, Plymouth University
6-7pm "Programming Robots with Natural Language"
(BCS Specialist Group in AI & KBS)
Tue 8th May David Gilbert, City University
5-6pm "Protein Topology - techniques for pattern matching,
pattern discovery and structure comparison"
Tue 15th May Jean Bacon and Ken Moody, Cambridge University
5-6pm "OASIS Access Control for Distributed Services"
Tue 5th June William Langdon, University College,
5-6pm "Advances in Genetic Programming"
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"Programming Robots with Natural Language"
Dr Guido Bugmann (University of Plymouth)
Future domestic robots will need to adapt to the special needs of their users
and to their environment. Programming by natural language will be a key method
enabling computer language-naive users to instruct their robots. Its main
advantages over other learning methods are speed of acquisition and ability to
build high level symbolic rules into the robot.
The presentation describes initial steps and considerations towards the design
of a practical system in which users teach a vision-based robot how to
navigate in a miniature town. Users will use unconstrained speech within a
restricted domain-specific lexicon determined by analysing a corpus of route
instructions. This is expected to maximise speech recognition performance.
The robot knows a set of primitive navigation procedures that the user can
refer to when giving route instructions. The presentation reports on the
analysis of the corpus in terms of lexicon and primitive actions procedures.
It then elaborates on the system-wide constraints imposed by the use of
Instruction-Based Learning (IBL) and describes proposed solutions.
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Dr Guido Bugmann was born in 1953 and has two children. He studied Physics at
the University of Geneva in Switzerland. In 1986 he completed a PhD on
"Fabrication of photovoltaic solar cells with a-Si:H produced by anodic
deposition in a DC plasma". He has then worked at the Swiss Federal Institute
of Technology in Lausanne on the development of a measurement system using an
ultra-sound beam and neural networks to measure the size of air bubbles in
bacterial cultures.
In 1989 he joined the Fundamental Research Laboratories of NEC in Japan and
modelled the function of biological neurons in the visual system. In 1992 he
joined Prof. John G. Taylor at King's College London to develop applications
of the pRAM neuron model and develop a theory of visual latencies. In 1993 he
joined the group of Prof. Mike Denham at the University of Plymouth (UK) where
he develops vision-based navigation systems for robots, and investigates
biological planning and spatial memory. He supervises PhD students and teaches
neural computation at B.Sc. and M.Sc. level. Dr Bugmann has 3 patents and over
90 publications. He is member of the Swiss Physical Society, The Neuroscience
Society and The British Machine Vision Association.
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Protein Topology - techniques for pattern matching, pattern discovery and
structure comparison
David Gilbert
Department of Computing, City University, London EC1V 0HB, UK
drg@soi.city.ac.uk, www.soi.city.ac.uk/~drg
We present a formal description of protein topology based on TOPS
representations of protein structures. These comprise Secondary Structure
Elements (SSEs), beta-sheet connectivities and certain chiralities.
We have also defined topological patterns which are like structure
descriptions with inserts of SSEs permitted between pattern SSEs. We have
developed a pattern matching algorithm which exploits the constraints imposed
by the ordering on SSEs to prune the search space. Our pattern discovery
technique works by repeated pattern matching and pattern extension and is
of complexity linear in the number of examples. We have developed a method
to divide a set of protein domains into subsets each with its own
characteristic pattern, using a rating function based on the "goodness" of
the pattern (using a compression measure) and their coverage of the example
set. Such unions of patterns can be used to characterise the CATH or SCOP
protein hierarchy with greater discrimination than simple (non-union)
patterns.
In addition a distance between two proteins can be computed by using a
common discovered pattern to produce a structural alignment of their SSE
sequences, and then computing a sum of the edit distances over non-matching
subsequences plus a penalty for non-matched arcs (hbonds and chiralities).
This work is collaborative with David Westhead (Leeds, UK) and Juris Viksna
(Latvia).
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OASIS Access Control for Distributed Services
Jean Bacon and Ken Moody
University of Cambridge Computer Laboratory
OASIS is a role-based access control architecture for achieving secure
interoperation of independently managed services in an open, distributed
environment. OASIS differs from traditional RBAC in a number of ways: role
management is decentralised, roles are parametrised, roles are activated in the
context of a session and privileges are not delegated.
Services define roles and implement formally specified policy for role
activation and service use; users must present the required
credentials, in the specified context, in order to activate a role or
invoke a service. The membership rule of a role indicates which of the
role activation conditions must remain true for the role to remain active.
A role is deactivated immediately if any of the conditions
of the membership rule associated with its activation become false.
This is achieved by building OASIS above event-based middleware.
Unlike traditional RBAC, OASIS does not use privilege delegation and static
role hierarchies but instead defines the notion of appointment,
whereby being active in certain roles
carries the privilege of issuing appointment certificates to other users.
Appointment certificates
capture the notion of long lived credentials such as academic and
professional qualification or membership of an organisation. The role
activation conditions of services may include appointment certificates,
prerequisite roles and environmental constraints.
We define the OASIS model and architecture and discuss engineering
issues.