Search results for "ubiquitous services"

Hits ?▲	Authors	Title	Venue	Year	Link	Author keywords
3	Tim Kindberg, Chris Bevan, Eamonn O'Neill, James Mitchell, Jim Grimmett, Dawn Woodgate	Authenticating ubiquitous services: a study of wireless hotspot access.	UbiComp	2009	DBLP DOI BibTeX RDF	authentication, wi-fi, phishing, ubiquitous services
2	Giliard Brito de Freitas, César Augusto Camillo Teixeira	Ubiquitous services in home networks offered through digital TV.	SAC	2009	DBLP DOI BibTeX RDF	UPnP™, interoperability, home network, digital TV, content delivery
2	Ana Petric, Krunoslav Trzec, Kresimir Jurasovic, Vedran Podobnik, Gordan Jezic, Mario Kusek, Igor Ljubi	Agent-Based Support for Context-Aware Provisioning of IMS-Enabled Ubiquitous Services.	SOCASE	2009	DBLP DOI BibTeX RDF	context-aware service provisioning, IMS-enabled services, multi-agent system, session mobility
2	Yun-Young Hwang, Hyung-Jun Yim, Il-Jin Oh, Kyu-Chul Lee	The Universal Adaptor for Dynamic Ubiquitous Services Discovery and Binding.	CSSE	2008	DBLP DOI BibTeX RDF
2	Ben-Shung Chow	A Very Low Bit Rate Video Coding for Ubiquitous Services.	MUE	2008	DBLP DOI BibTeX RDF	video coding, motion compensation, very low bit rate
2	Hideyuki Tokuda	Challenges in creating embedded ubiquitous services everywhere.	ESTImedia	2008	DBLP DOI BibTeX RDF
2	Yingli Sheng, Haitham S. Cruickshank, A. Dev Pragad, Paul Pangalos, A. Hamid Aghvami	An integrated QoS, security and mobility framework for delivering ubiquitous services across all IP-based networks.	PIMRC	2008	DBLP DOI BibTeX RDF
2	Yingli Sheng, Haitham S. Cruickshank	Security mechanisms for delivering ubiquitous services in next generation mobile networks.	PIMRC	2008	DBLP DOI BibTeX RDF
2	Claudio S. Pinhanez	Ubiquitous Services.	IEEE SCC	2007	DBLP DOI BibTeX RDF
2	Hideyuki Tokuda	Challenges in Creating New Context-aware Ubiquitous Services.	CEC/EEE	2007	DBLP DOI BibTeX RDF
2	Mitsuhiko Karashima, Yuko Ishibashi	Unconscious Transmission Services of Human Feelings.	HCI	2007	DBLP DOI BibTeX RDF	transmission of feelings, ubiquitous services
2	Ohbyung Kwon, Jihoon Kim	A Methodology for Assessing the Level of U-Transformation of Ubiquitous Services.	UCS	2006	DBLP DOI BibTeX RDF
2	Yasue Kishino, Tsutomu Terada, Shojiro Nishio	Ubiquitous Gadgets for Constructing Flexible Ubiquitous Services.	MDM	2006	DBLP DOI BibTeX RDF
2	Jae Yeol Lee, Gue Won Rhee, Hyun Kim, Kang-Woo Lee, Young-Ho Suh, Kwangsoo Kim	Convergence of Context-Awareness and Augmented Reality for Ubiquitous Services and Immersive Interactions.	ICCSA	2006	DBLP DOI BibTeX RDF
2	Kenichi Yamazaki	Research Directions for Ubiquitous Services.	SAINT	2004	DBLP DOI BibTeX RDF
2	Venu Vasudevan	Ensembleware: Contextual Service Provisioning in an Ubiquitous Services World.	SAINT	2004	DBLP DOI BibTeX RDF
1	Hideyuki Tokuda, Jin Nakazawa	SenseCampus: Sensor enabled Cyber-Physical Coupling for Ubiquitous Services.	JIP	2012	DBLP DOI BibTeX RDF
1	Andreas Rieger	Framework for Building Situation-Aware Ubiquitous Services in Smart Home Environments.		2011	RDF
1	Sheng-Yuan Yang	OntoIAS: An ontology-supported information agent shell for ubiquitous services.	Expert Syst. Appl.	2011	DBLP DOI BibTeX RDF
1	Hideyuki Tokuda, Jin Nakazawa, Takuro Yonezawa	Ubiquitous Services: Enhancing Cyber-Physical Coupling with Smart Enablers.	IEICE Transactions	2011	DBLP BibTeX RDF
1	Hai Dong, Farookh Khadeer Hussain, Elizabeth Chang	A framework for discovering and classifying ubiquitous services in digital health ecosystems.	J. Comput. Syst. Sci.	2011	DBLP DOI BibTeX RDF
1	Sunwook Kim, Seongwoon Kim, Kyoung Park, Yongwha Chung	Offloading Socket Processing for Ubiquitous Services.	J. Inf. Sci. Eng.	2011	DBLP BibTeX RDF
1	Shu-Ching Wang, Jen-Her Wu	Proactive Privacy Practices In The Trend Of Ubiquitous Services: An Integrative Social Contracts Perspective.	PACIS	2011	DBLP BibTeX RDF
1	Heejung Chang, Kangsun Lee	A Quality-Driven Web Service Composition Methodology for Ubiquitous Services.	J. Inf. Sci. Eng.	2010	DBLP BibTeX RDF
1	Were Oyomno, Pekka Jäppinen, Esa Kerttula	Privacy Policy Enforcement for Ambient Ubiquitous Services.	AmI	2010	DBLP DOI BibTeX RDF
1	Ileana Buhan, Gabriele Lenzini, Sasa Radomirovic	Contextual Biometric-Based Authentication for Ubiquitous Services.	UIC	2010	DBLP DOI BibTeX RDF
1	Seng Wai Loke	Building Taskable Spaces over Ubiquitous Services.	IEEE Pervasive Computing	2009	DBLP DOI BibTeX RDF
1	Ching-Hsien Hsu, Jong Hyuk Park, Laurence Tianruo Yang, Mário M. Freire	Secure communications and data management in ubiquitous services.	Int. J. Communication Systems	2009	DBLP DOI BibTeX RDF
1	Romain Rouvoy, Frank Eliassen, Mikaël Beauvois	Dynamic planning and weaving of dependability concerns for self-adaptive ubiquitous services.	SAC	2009	DBLP DOI BibTeX RDF	planning-based adaptation, quality of service, aspect-oriented programming, component-based software engineering
1	Antero Metso, Petri Pulli, Seamus Hickey, Xiaosong Zheng	Ubiquitous Services for Senior Citizens - Living Process Detection and Middleware.	ACIS-ICIS	2009	DBLP DOI BibTeX RDF
1	Zeeshan Asghar, Seamus Hickey, Shaista Kazmi	Developing mobile services for specific user groups using virtual environments.	MUM	2009	DBLP DOI BibTeX RDF	virtual environments, mobile services, elderly, QFD
1	Ali Yachir, Karim Tari, Yacine Amirat, Abdelghani Chibani, Nadjib Badache	QoS based framework for ubiquitous robotic services composition.	IROS	2009	DBLP DOI BibTeX RDF
1	Andreas Emrich, Alexandra Chapko, Dirk Werth	Context-Aware Recommendations on Mobile Services: The m: Ciudad Approach.	EuroSSC	2009	DBLP DOI BibTeX RDF	m:Ciudad, user-generated services, recommendations, mobile services, proactivity
1	Kristina Höök	Mobile Life - Innovation in the Wild.	INTERACT	2009	DBLP DOI BibTeX RDF
1	Artur Lugmayr, Simon Reymann, Volker Bruns, Jakub Rachwalski, Stefan Kemper	Distributing the personal digital environment throughout your entertainment environment: handling personal metadata across domains.	Multimedia Syst.	2009	DBLP DOI BibTeX RDF	Context profile, Portable personality, P2, Ubiquitous computation, Context awareness, Personalization, Metadata, Pervasive computation, Ambient media, Personal profile, Personality profile
1	Xuefeng Liang, Naixue Xiong, Laurence Tianruo Yang, Hui Zhang, Jong Hyuk Park	A compensation scheme of fingerprint distortion using combined radial basis function model for ubiquitous services.	Computer Communications	2008	DBLP DOI BibTeX RDF
1	Alistair P. Barros	Ubiquitous Services and Business Processes.	Handbook of Research on Ubiquitous Computing Technology for Real Time Enterprises	2008	DBLP BibTeX RDF
1	Jong-Hwan Kim, Chi-Ho Lee, Kang-Hee Lee, Naveen Suresh Kuppuswamy	Evolutionary Generation of Artificial Creature's Personality for Ubiquitous Services.	Advances in Metaheuristics for Hard Optimization	2008	DBLP DOI BibTeX RDF
1	Athman Bouguettaya	Infrastructure for Ubiquitous Services.	ADC	2008	DBLP BibTeX RDF
1	Sheng-Yuan Yang	Developing of an Ontological Focused-Crawler for Ubiquitous Services.	AINA Workshops	2008	DBLP DOI BibTeX RDF
1	Takeshi Tsuchiya, Marc Lihan, Hirokazu Yoshinaga, Kei'ichi Koyanagi	Distributed Information Retrieval Service for Ubiquitous Services.	ARES	2008	DBLP DOI BibTeX RDF	Peer-to-Peer: Information Retrieval
1	A. Dev Pragad, George Kamel, Paul Pangalos, A. Hamid Aghvami	A combined mobility and QoS framework for delivering ubiquitous services.	PIMRC	2008	DBLP DOI BibTeX RDF
1	Merat Shahidi, Abdelhak Attou, Hamid Aghvami	Content adaptation: requirements and architecture.	iiWAS	2008	DBLP DOI BibTeX RDF	adaptation management, content adaptation, ubiquitous services
1	Chen-Shu Wang, Yeu-Ruey Tzeng	A Wireless Networking Technologies Overview Over Ubiquitous Service Applications.	NCM	2008	DBLP DOI BibTeX RDF	U-commerce, U-Manufacture, U-health, Wireless technology, Ubiquitous Services, U-learning
1	Oriana Riva, Josiane Nzouonta, Cristian Borcea	Context-aware fault tolerance in migratory services.	MobiQuitous	2008	DBLP DOI BibTeX RDF	context-aware fault tolerance, migratory services, mobile ad hoc networks
1	Tsuyoshi Shinno, Kazunori Hashizume, Junichi Tajima, Shigeo Kaneda, Hirohide Haga	Detection of multiple human location and direction by integrating different kinds of sensors.	PETRA	2008	DBLP DOI BibTeX RDF	contextual awareness, individual identification, ubiquitous computing, location tracking
1	Eric J. Ballance, Hwajung Lee	Developing Proactive Information Delivery System through Bluetooth in Ubiquitous Networks.	MUE	2008	DBLP DOI BibTeX RDF	Ubiquitous and Pervasive Computing, Bluetooth, Ubiquitous Networks, Information Delivery
1	Chenn-Jung Huang, Hong-Xin Chen, I-Fan Chen, Kai-Wen Hu	A Location-Aware Resource Management Scheme for Ubiquitous Wireless Networks.	MUE	2008	DBLP DOI BibTeX RDF	ubiquitous computing, resource management, heterogeneous wireless network, location-aware computing, SDMA
1	Kentaro Fujiwara, Yuuichi Teranishi, Susumu Takeuchi, Kaname Harumoto, Shojiro Nishio	An Implementation of Lightweight Message Transport Mechanism for P2P Agent Platform on Ad-Hoc Networks.	SAINT	2008	DBLP DOI BibTeX RDF	Lightweight Message, Ad-hoc Network, P2P, Ubiquitous
1	Wei-Tsung Su, Ing-Hsiu Liao, Kuan-Rong Lee, Yau-Hwang Kuo	Service-Oriented Device Composition in Resource Constrained Ubiquitous Environments.	WCNC	2008	DBLP DOI BibTeX RDF
1	Fernando Lyardet, Diego Wong Szeto, Erwin Aitenbichler	Context-Aware Indoor Navigation.	AmI	2008	DBLP DOI BibTeX RDF
1	Joo Hwan Lee, Joobong Song, Hyungsup Kim, Junyoung Choi, Myung Hwan Yun	A User-Centered Approach for Ubiquitous Service Evaluation: An Evaluation Metrics Focused on Human-System Interaction Capability.	APCHI	2008	DBLP DOI BibTeX RDF	User-Centered Design Evaluation, Usability Evaluation Method (UEM), Interactivity, ubiquitous Service
1	Patrik Spieß, Dinh Khoa Nguyen, Ingo Weber, Ivan Markovic, Michael Beigl	Modelling, Simulation, and Performance Analysis of Business Processes Involving Ubiquitous Systems.	CAiSE	2008	DBLP DOI BibTeX RDF
1	Youna Jung, Amirreza Masoumzadeh, James B. D. Joshi, Minkoo Kim	RiBAC: Role Interaction Based Access Control Model for Community Computing.	CollaborateCom	2008	DBLP DOI BibTeX RDF	Role interaction, Multiagent system, Role-based Access Control, Cooperation, Community computing
1	Tai-Jong Kim, Min-Cheol Kim	Context Awareness Using Semantic Web Technology in the Ubiquitous Learning Service.	ICCSA	2008	DBLP DOI BibTeX RDF	u-Learning service, ontology, semantic web, context awareness, intelligent web service
1	Jonas Kuschel	The Vehicle Ecosystem.	Open IT-Based Innovation	2008	DBLP DOI BibTeX RDF	services, Information infrastructure, open innovation, ecosystem
1	Fosca Giannotti, Dino Pedreschi, Franco Turini	Mobility, Data Mining and Privacy the Experience of the GeoPKDD Project.	PinKDD	2008	DBLP DOI BibTeX RDF
1	Ohbyung Kwon, Yonnim Lee	A Structured Methodology of Scenario Generation and System Analysis for Ubiquitous Smart Space Development.	UIC	2008	DBLP DOI BibTeX RDF	ubiquitous smart space, requirement analysis, scenario analysis, structured method
1	Takuro Yonezawa, Hiroshi Sakakibara, Kengo Koizumi, Shingo Miyajima, Jin Nakazawa, Kazunori Takashio, Hideyuki Tokuda	uPackage - A Package to Enable Do-It-Yourself Style Ubiquitous Services with Daily Objects.	UCS	2007	DBLP DOI BibTeX RDF
1	Takeshi Tsuchiya, Hirokazu Yoshinaga, Kei'ichi Koyanagi	Decentralized Information Retrieval Systems Based on Contents Information for Ubiquitous Services.	AINA Workshops	2007	DBLP DOI BibTeX RDF	statistic information of contents, peer-to-peer, overlay network, distributed searching
1	Yoshikazu Tokairin, Kazuhiro Yamanaka, Hideyuki Takahashi, Takuo Suganuma, Norio Shiratori	An Effective QoS Control Scheme for Ubiquitous Services based on Context Information Management.	CEC/EEE	2007	DBLP DOI BibTeX RDF
1	Jonghun Park, Wan Lee, Jae-Yoon Jung, Kangchan Lee	Incorporation of User Preferences into Mobile Web Service Conversations.	HCI	2007	DBLP DOI BibTeX RDF	Web service choreography, Conversation preference, Mobile web services, WS-CDL, Ubiquitous services
1	HyunBin Lee, YongJoo Song, Kyungbaek Kim, Donggook Kim, Daeyeon Park	CriStore: dynamic storage system for heterogeneous devices in off-site ubiquitous communities.	SAC	2007	DBLP DOI BibTeX RDF	dynamic storage system, flexible overlay topology, off-site ubiquitous community, self-organizing, heterogeneity
1	Paolo Bellavista	"Middleware for Next-Generation Converged Networks and Services: Myths or Reality?".	COMPSAC	2007	DBLP DOI BibTeX RDF
1	Eun-Jun Yoon, Kee-Young Yoo	Two Security Problems of Efficient Remote Mutual Authentication and Key Agreement.	FGCN	2007	DBLP DOI BibTeX RDF	Authentication, Cryptanalysis, Smart card, Password, Key agreement
1	Yang-Min Lee, Bong-Soon Kang, Jae-Kee Lee	A Study on a highly-reliable Multi-path Configuration protocol in Ubiquitous Network by MANET.	MUE	2007	DBLP DOI BibTeX RDF
1	Robert C. Meurant	On the Obliquity of Ubiquity.	MUE	2007	DBLP DOI BibTeX RDF
1	Toshihiko Yamakami	MobileWeb 2.0: Lessons from Web 2.0 and Past Mobile Internet Development.	MUE	2007	DBLP DOI BibTeX RDF
1	Yong Song, SangKwon Moon, Gyudong Shim, Daeyeon Park	mu-ware: A Middleware Framework for Wearable Computer and Ubiquitous Computing Environment.	PerCom Workshops	2007	DBLP DOI BibTeX RDF
1	Manfred Bortenschlager, Gabriele Kotsis, Marco Mamei, Nicola Bicocchi, Gabriella Castelli, Alberto Rosi, Franco Zambonelli	CoMA Workshop Final Report.	WETICE	2007	DBLP DOI BibTeX RDF
1	Rodrigo Roman, Cristina Alcaraz	Applicability of Public Key Infrastructures in Wireless Sensor Networks.	EuroPKI	2007	DBLP DOI BibTeX RDF	Wireless Sensor Networks, Public Key Cryptography, Public Key Infrastructure
1	Shigeyoshi Iizuka, Yurika Katagiri	Design for Confident Communication of Information in Public Spaces.	HCI	2007	DBLP DOI BibTeX RDF	Reassurance, Public Space, Personal Space
1	Taekyoung Kwon, Sang-ho Park, Sooyeon Shin	Multi-modal Authentication for Ubiquitous Computing Environments.	HCI	2007	DBLP DOI BibTeX RDF
1	Haining Lee, Jaeil Park, Peom Park, Myungchul Jung, Dongmin Shin	Dynamic Conflict Detection and Resolution in a Human-Centered Ubiquitous Environment.	HCI	2007	DBLP DOI BibTeX RDF	human-centered ubiquitous environment, resolution, human interaction, Conflicts detection
1	Gregory M. P. O'Hare, Michael J. O'Grady, Conor Muldoon, Caroline A. Byrne	Ambient Documents: Intelligent Prediction for Ubiquitous Content Access.	HCI	2007	DBLP DOI BibTeX RDF	ambient documents, Ubiquitous computing, intelligent agents, Ambient Intelligence
1	Hyemee Park, KwangJin Park, Tae-Jin Lee, Hyunseung Choo	A Network Framework on Adaptive Power Management in HCI Mobile Terminals.	HCI	2007	DBLP DOI BibTeX RDF	MANET routing, Clustering, Mobile HCI
1	Hun-Soon Lee, Seung-Il Jin	An Effective XML-Based Sensor Data Stream Processing Middleware for Ubiquitous Service.	ICCSA	2007	DBLP DOI BibTeX RDF	context-driven service, ubiquitous computing, middleware, continuous query, sensor data
1	Jong Sik Moon, Im-Yeong Lee	A Study on Ticket-Based AAA Mechanism Including Time Synchronization OTP in Ubiquitous Environment.	ICCSA	2007	DBLP DOI BibTeX RDF	OTP, Authentication, Ubiquitous, AAA, Ticket
1	Binod Vaidya, SangDuck Lee, Eung-Kon Kim, Seung Jo Han	Streaming Media Securely over Multipath Multihop Wireless Network.	PAKDD Workshops	2007	DBLP DOI BibTeX RDF
1	Youna Jung, Jungtae Lee, Minkoo Kim	Community Computing Model Supporting Community Situation Based Strict Cooperation and Conflict Resolution.	SEUS	2007	DBLP DOI BibTeX RDF
1	Theodore Patkos, Antonis Bikakis, Grigoris Antoniou, Maria Papadopouli, Dimitris Plexousakis	A Semantics-Based Framework for Context-Aware Services: Lessons Learned and Challenges.	UIC	2007	DBLP DOI BibTeX RDF
1	Akio Sashima, Noriaki Izumi, Koichi Kurumatani, Yoshiyuki Kotani	Toward Role-based Agent Coordination for Mobile and Ubiquitous Services.	AINA	2006	DBLP DOI BibTeX RDF
1	Shigetoshi Yokoyama, Eiji Kamioka, Shigeki Yamada	An Anonymous Context Aware Access Control Architecture For Ubiquitous Services.	MDM	2006	DBLP DOI BibTeX RDF
1	Srisakul Thakolsri, Christian Schaefer, Thomas Walter, Wolfgang Kellerer	Accounting management for session mobility in an ubiquitous environment.	IWCMC	2006	DBLP DOI BibTeX RDF	accounting, session mobility
1	Eduardo Cerqueira, Paulo Mendes, Edmundo Monteiro	Multi-user session control in the next generation wireless system.	MOBIWAC	2006	DBLP DOI BibTeX RDF	heterogeneous wireless systems, multi-user session, quality of service
1	Carlos Alberto Kamienski, Djamel Sadok, Joseane Farias Fidalgo, Jennifer Lima, Börje Ohlman	On the Use of Peer-to-Peer Architectures for the Management of Highly Dynamic Environments.	PerCom Workshops	2006	DBLP DOI BibTeX RDF
1	Kyung-Lang Park, Joo-Kyoung Park, Chang-Deok Kang, Hoon-Ki Lee, Eui-Hyun Baek, Shin-Dug Kim	VPW: An Effective Personal Space Model for Providing Ubiquitous.	SERA	2006	DBLP DOI BibTeX RDF
1	Hui-Juan Yao, Geng-Sheng Kuo	Dynamic Point Forwarding Scheme for QoS-aware Mobility in Future All-IP Wireless Networks.	VTC Spring	2006	DBLP DOI BibTeX RDF
1	Shafique Ahmad Chaudhry, Faysal Adeem Siddiqui, Ali Hammad Akbar, Ki-Hyung Kim	NETSAQ: Network State Adaptive QoS Provisioning for MANETs.	APNOMS	2006	DBLP DOI BibTeX RDF	Network state Adaptive, Policy-based QoS provisioning, QoS, Mobile ad-hoc networks (MANETs), QoS routing
1	Jianhua Ma, Qiangfu Zhao, Vipin Chaudhary, Jingde Cheng, Laurence Tianruo Yang, Runhe Huang, Qun Jin	Ubisafe Computing: Vision and Challenges (I).	ATC	2006	DBLP DOI BibTeX RDF
1	Shiqun Li, Shane Balfe, Jianying Zhou, Kefei Chen	Enforcing Trust in Pervasive Computing with Trusted Computing Technology.	CRITIS	2006	DBLP DOI BibTeX RDF
1	Binod Vaidya, SangDuck Lee, Jae-Kyun Han, Seung Jo Han	Authentication Mechanism Using One-Time Password for 802.11 Wireless LAN.	CSR	2006	DBLP DOI BibTeX RDF
1	Binod Vaidya, YoungJin Kim, Eung-Kon Kim, Seung Jo Han	Investigating Authentication Mechanisms for Wireless Mobile Network.	UIC	2006	DBLP DOI BibTeX RDF
1	Rahat Iqbal, Janienke Sturm, Olga A. Kulyk, Jimmy Wang, Jacques M. B. Terken	User-centred design and evaluation of ubiquitous services.	SIGDOC	2005	DBLP DOI BibTeX RDF	peripheral feedback, ubiquitous/pervasive computing, evaluation, meetings, human-human interaction, social dynamics, lectures
1	Hideyuki Takahashi, Yoshikazu Tokairin, Takuo Suganuma, Norio Shiratori	Design and Implementation of an Agent-Based Middleware for Context-Aware Ubiquitous Services.	SoMeT	2005	DBLP BibTeX RDF
1	Nishkam Ravi, Peter Stern, Niket Desai, Liviu Iftode	Accessing Ubiquitous Services Using Smart Phones.	PerCom	2005	DBLP DOI BibTeX RDF
1	Hideyuki Takahashi, Takuo Suganuma, Norio Shiratori	AMUSE: An Agent-based Middleware for Context-aware Ubiquitous Services.	ICPADS	2005	DBLP DOI BibTeX RDF
1	Lina Peng, K. Selçuk Candan	Confidence-driven early object elimination in quality-aware sensor workflows.	DMSN	2005	DBLP DOI BibTeX RDF	sensor workflows, data stream management
1	Eiji Tokunaga, Hiroaki Kimura, Nobuyuki Kobayashi, Tatsuo Nakajima	Virtual tangible widgets: seamless universal interaction with personal sensing devices.	ICMI	2005	DBLP DOI BibTeX RDF	personal mobile devices, universal controllers, virtual tangible user interface, ubiquitous computing, interaction techniques, handheld augmented reality
1	Liliana Ardissono, Anna Goy, Giovanna Petrone, Marino Segnan	A multi-agent infrastructure for developing personalized web-based systems.	ACM Trans. Internet Techn.	2005	DBLP DOI BibTeX RDF	Infrastructures for developing personalized recommender systems, personalization, multi-agent architectures