Semantic Email Addressing The Semantic Web Killer App

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					                 Semantic Email Addressing: The Semantic Web Killer App?

                 Michael Kassoff, Charles Petrie, Lee-Ming Zen and Michael Genesereth
                                          Logic Group, Department of Computer Science
                                                        Stanford University
                                        {mkassoff, petrie, leezen, genesereth}@stanford.edu




                           Abstract                                 No discovery required. Email addresses and mailing
  In this document, we explore how semantic technologies can
                                                                    lists can be difficult to discover, even for a human. Worse,
  be brought to email addressing. We introduce the notion of        since email addresses and mailing list names have no
  semantic email addressing (SEA). SEA allows emails to be          semantics, automatic discovery of email addresses and
  sent to a semantically specified recipient of group of recipi-     mailing lists by a computer is an extremely difficult task,
  ents, which may be dynamically changing over time. We give        if not impossible. With SEA, discovery is completely
  some applications of SEA and describe our prototype imple-        obviated.
  mentation.
                                                                    No maintenance required.         Traditional mailing lists
                       Introduction                                 require manual labor to maintain. A mailing list adminis-
Email addresses, like telephone numbers, are opaque iden-           trator must go through the process of creating the list. The
tifiers. They are often hard for a person to remember, and           list must then be maintained by the administrator himself
worse still, people’s email addresses and phone numbers             and the individuals who would like to subscribe to the list,
change from time to time.                                           unsubscribe to the list, and change their information with
   Email addresses are a means to an end. One’s goal is             regards to the list. This can be particularly onerous when
usually not to send an email to a particular address, but in-       the user must deal with many lists, for example when his
stead to a particular person. One wants to say hello to our         email address changes. Ideally, the user could update his
friend Steve, or send a message to the VP of marketing at           personal information such as email address once, in a single
Microsoft, or to the head caterer for one’s wedding. Ideally,       place, and have email addressers automatically adapt. SEA
one could send a message to a person just by entering his           makes this possible.
name, his position, or some other descriptive attributes. If
the email address of a person changes, then the email system           The rest of this paper is organized as follows. We first
should send to the new email address, automatically. If the         describe some applications of SEA. Next, we explain how
person matching a description differs over time, the email          one can send and reply to messages using SEA, and discuss
system should always send to the person currently matching          our prototype implementation called ISEA. We then explore
that description.                                                   a few issues raised by SEA, including security and privacy
   More generally, one should be able to send emails to             issues, errors, user adoption, and standardization. Finally,
groups of people matching a particular set of attributes: all       we describe related and future work.
chairs of departments at Stanford, or all female customers
living in Detroit, or all people in our organization who speak                                Examples
both English and French.                                            To illustrate semantic email addressing, we consider two ex-
   Today, mailing lists are used to email predefined groups of       amples. The first illustrates SEA in a controlled, corporate
people. However, as there are infinitely many ways to define          environment. The second illustrates the use of SEA using
a set of people (e.g.“all people in the marketing department        public information gathered from the Internet.
whose name starts with the letter ‘M’ ”), one cannot in gen-
eral rely on such predefined lists. Instead, one must have the       Corporate Example
ability to address our email arbitrary groups of people.            Corporations and other organizations often have databases
   We use the term semantic email addressing (SEA) to refer         of information about personnel, projects, customers, and so
to emails that are addressed to a semantically defined set of        on. This information can be leveraged to send emails based
entities. The recipients to a semantically addressed email          on properties of the people in the department.
are computed on the fly based on the semantic definition of              As an example, consider a moderate size company
the address.                                                        with several departments. The company has a centralized
   SEA has other benefits as well:                                   database containing the following information about com-
                                                                    pany personnel:
<foaf:name>Charles Petrie</foaf:name>
<foaf:workplaceHomepage rdf:resource="http://www.stanford.edu/"/>
<foaf:interest rdf:resource="http://en.wikipedia.org/wiki/BMW_motorcycles#R_series"/>
<foaf:interest rdf:resource="http://en.wikipedia.org/wiki/German_language"/>
<foaf:interest rdf:resource="http://en.wikipedia.org/wiki/Semantic_Research"/>
<foaf:mbox rdf:resource="mailto:petrie@stanford.edu"/>
<foaf:knows>
  <foaf:Person>
    <foaf:name>Axel Polleres</foaf:name>
    <rdfs:seeAlso rdf:resource="http://www.polleres.net/foaf.rdf"/>
  </foaf:Person>
</foaf:knows>

                            Figure 1: Fragment of Charles Petrie’s FOAF (Friend-of-a-Friend) profile


                                                                   predicates for expressing properties of a person such as their
Name                                                               name, email address, group memberships, employer, gender,
Email Address                                                      birthday, interests, projects and acquaintances. As of 2004,
Department                                                         over 1.25 million FOAF documents were publicly available
Group                                                              on the Internet, and that number has certainly grown since
Position                                                           (Ding et al. 2005).
Project                                                               By spidering the Semantic Web and collecting the infor-
Date of Hire                                                       mation contained in these FOAF files, one can build up a
                                                                   large collection of data about people and their interests. This
   Given this information, one may define groups of people          information can then be used to email people with a given
by querying the data, for example for “all senior managers         interest, or who know people who know a particular person,
in the accounting department.” If the company also has the         and so on. To illustrate, a fragment of one of the authors’
following information about projects:                              FOAF file is shown in Figure 1. As you can see, Charles
                                                                   is a Stanford employee interested in BMW R series mo-
Project Name                                                       torcycles, German, and semantic research, and knows Axel
Priority                                                           Polleres. Note that using this information and similar in-
Leader                                                             formation culled from various other FOAF files, one could
Start Date                                                         address an email to all Stanford employees interested in se-
End Date                                                           mantic research, or all people interested in R series motor-
                                                                   cycles, and so on.
   One may then define precise groups of people such as “all           Note how his FOAF file is a single place in which Charles
developers for current projects in the Database group.” Us-        can control his personal information - if Charles were to
ing semantic email addressing, one may then send an email          change his email address, then all semantically addressed
to this group. Like a traditional mailing list, a recipient of a   email based on his FOAF profile would be automatically
semantic email address may respond to the sender or to the         routed to his new address. If Charles were to leave Stan-
group itself. Unlike a traditional mailing list, the recipient     ford, then he would no longer receive emails addressed to
may respond to a particular subset of the group, or forward        Stanford people interested in semantic research. All of this
the email to some other semantically defined group of peo-          is under Charles’ control, without the need to change his
ple.                                                               settings with each mailing list individually. It all happens
   Using semantic email addressing, it would be easy for           automatically.
a computer to send an email to a specific person or group              In a sense, SEA is the opposite of spam. While both SEA
of persons. For example, the company room reservation              and spam may involve unsolicited emails, spam is sent to ev-
system could straightforwardly be programmed to automat-           eryone, while SEA is targeted towards those who have pub-
ically send an email to the building manager each time con-        licly announced they are interested in it. SEA is a marketer’s
ference room 101 was reserved, without knowing who the             dream come true.
building manager is. As the employee serving as building              Note also that, unlike mailing lists, there is no discovery
manager changed over time, the email would always be sent          required for either the sender or the receiver. It just works.
to the correct person, without having to reprogram the room           Of course, we don’t have to depend just upon FOAF de-
reservation system.                                                scriptions. We can also integrate semantic information from
                                                                   various sources, such as RDF files or relational databases.
Internet Example                                                   For example, we might also pull bibliographic information
Recently, a RDF ontology known as FOAF, or Friend-of-              from a site such as DBLP, and email everyone who has ever
a-Friend, has gained in popularity. This ontology contains         coauthored a paper with Charles and whose email address is
       Figure 2: Sending email to members of the group lead by Michael Genesereth interested in logical spreadsheets


publicly available.                                              tology, either the user either be able to specify a query in
                                                                 the ontology directly, say via a textual editor, or he must
        Using Semantic Email Addressing                          use some sort of tool to that facilitates query formulation
                                                                 in that ontology. As only power users can be expected to
Now that we have motivated the myriad benefits of SEA,            formulate queries directly, a graphical interface for query
we delve into some practical details. How should it work?        creation is useful here. To support the possibility of using
We first talk about sending semantically addressed email,         various ontologies, the tool should be generic and generate
then we talk about how one might reply to a semantically         query interfaces on the fly based on the ontology and some
addressed email.                                                 display metadata. The interface used by our prototype is
   To allow the user to semantically specify a set the email     shown in Figure 2. The interface is automatically generated
addresses to which to send to, there are three somewhat sep-     based on the schema for a person and some metadata about
arable pieces of functionality required. First, the user must    how to display each field, for example as a text box or a
be able to define the group of email addresses of interest.       drop down list. Here, an email is being sent to members
This might involve choosing from some predefined list of          of the group lead by Michael Genesereth interested in logi-
definitions; though to attain the full power of semantic email    cal spreadsheets. Note that it allows the emailer to define a
addressing, the user should be able to formulate new defini-      set of people as opposed to a set of email addresses. As each
tions. The second piece of functionality is that the definition   person is associated with at most one email address, this also
must somehow be translated to a set of email addresses to        unambiguously defines the set of email addresses to send the
which the email must be sent. The final piece of function-        message to.
ality is to facilitate replying in a simple manner. This final       Note how the interface of ISEA allows embedded queries
piece is optional but sometimes useful.                          of arbitrary depth to be formed. For example, one might
   An email client that allows for SEA requires only some        query for all people at a site that is in a country where French
small extensions over a traditional email client. In our pro-    is spoken. This cross-category search is particularly useful
totype, the interface for composing a message looks just like    when large amounts of supporting information are available.
a traditional interface, with To, Cc, Bcc, Subject and Body      In particular, consider that if the Semantic Web becomes a
fields. The only difference is an extra button, which allows      reality, then one will have the possibility of basing his query
a semantic email address to be specified wherever a tradi-        on arbitrary information on the Web.
tional email address can be placed. This functionality is           Semantic email addressing is a powerful tool, which could
similar to the address book functionality found in modern        easily be used to email large numbers of people. Safeguards
email clients. Upon pressing the button, a window pops up        must be put in place to make sure that user errors do not
with an interface for defining a set of recipients.               result in a mass spamming. It is useful to give the user feed-
   Since a definition must be formulated in a particular on-      back on his query definition by displaying a list of people
                                                                        the case that the email client supports semantic email ad-
                                                                        dressing, or by clicking a Web page link automatically gen-
                                                                        erated by the system and placed in the footer of the message
                                                                        by the sending agent. The latter is a bit more tricky, for the
                                                                        reason that the set of email addresses defined by a particular
                                                                        query may change over time. In the case that the number of
                                                                        email addresses is small, the actual email addresses to which
  Figure 3: Confirmation page shown after pressing send                  the email was sent might appear in the To or Cc fields of the
                                                                        email, but if the number of addresses is large, this becomes
                                                                        impractical. In this case, the sending agent must somehow
to which the email will be sent, in the case that the number            keep track of either the set of addresses sent to by each mes-
of people is sufficiently small that this can be done. Other-            sage or enough of the state of the database at each point in
wise, it is useful to display the number of people to which             time to reconstruct this information. Doing so in a space-
the email will be sent, along with a sample of those people.            efficient manner is an open problem.
This allows the user to catch errors in his query definition,               Replying to a semantically addressed email raises similar
and give him confidence that he is not accidentally sending a            issues. In the case that the addresses of the recipients are
large number of people a message not meant for them. Fig-               sent in the To or CC fields of the message, one can reply in
ure 3 shows a simple confirmation page displayed in ISEA                 the usual manner to the recipients of the original message,
after the send button is pressed after choosing the set of peo-         or they can use semantic email addressing to reply. In the
ple defined in Figure 2.                                                 case that the recipient list is not included in the message,
   As mentioned earlier, ISEA creates actual semantic email             semantic email addressing must be used to reply. However,
addresses that are essentially of the form query@domain.                note that the set of people satisfying a condition may change
For example, in our prototype system, by sending an email               over time, so replying can result in new people receiving the
to a properly encoded “People in the Logic Group interested             reply and old people not receiving the reply, which may or
in logical spreadsheets”@logic.stanford.edu, an email will              may not be the desired behavior. Of course, this is nothing
be sent to the appropriate people (where the quoted part is             new - the subscriber list to a traditional mailing list changes
replaced by an appropriate computer-interpretable string).              over time as well.
This is useful for sending mail from email clients that do
not support semantic email addressing, for adding seman-                                         Prototype
tic email addresses to one’s address book, etc. However, in             We have built a prototype SEA module on top of Infomaster
an ideal world in which all email clients supported seman-              (Genesereth et al. 1997) called ISEA (“Infomaster Semantic
tic email addressing, these semantic email addresses would              Email Addresser”). Infomaster is an information integration
be completely hidden from the user, as they are long, un-               engine, and can be used to query multiple sources of data
intelligible, and ugly.1 Instead of viewing such ungainly               on the Internet through a single mediated schema. This is
identifiers, we expect users to always view semantic email               useful for SEA because it allows information to be pulled
addresses though some graphical representation like the one             in from many sources - not just about people, but also use-
shown in Figure 2, or a human-readable textual description              ful supporting information about organizations and locations
such as one written in a controlled subset of English. In               and so forth.
our prototype, we also allow a short, human readable nick-                 The prototype is currently being used in a system used by
name to be associated with a semantic email address using               members of the Digital Enterprise Research Institute in four
the same mechanism that user names are associated with                  locations - Stanford, Galway, Innsbruck and Korea. Since
normal email addresses. In Figure 2, the nickname “Pred-                the institute is large and distributed, and members are fre-
iCalc Team” is given to the aforementioned semantic email               quently coming and going, it is hard for a member of the in-
address.                                                                stitute to keep track of who is where and doing what. Thus,
   Upon receiving a semantically addressed email, it is                 it is a natural application for SEA. The prototype allows
sometimes useful to give the receiver the ability to view both          people to be emailed based on their site, group affiliations,
the semantic definition of who the email was sent to and                 name, interests, and other attributes (see Figure 2). This in-
the actual people to whom the email was sent. The former                formation is obtained from private databases and publicly
can be accomplished by viewing the semantic email address               available FOAF files.
through an appropriate GUI or natural language display, in                 The ontology used by SEA is set by an administrator and
   1
                                                                        is thus centrally controlled, though it is continually evolving.
     In our prototype, the semantic email address of Figure 2 is rep-      The basic architecture of our prototype is as follows.
resented as sea+.28.3F5.20AND.20.28PERSON.2EGROUP.20.3F                 There are four principal components:
5.20.3F6.29.20.28GROUP.2ELEADER.20.3F6.20MICHAEL.2E
GENESERETH.29.20.28GROUP.2EINSTANCE.20.3F6.29.20.28
PERSON.2EINTEREST.20.3F5.20PERSONALINTEREST.2E33                        (1) A Web-based user interface that is used to con-
64062876.29.20.28PERSON.2EINSTANCE.20.3F5.29.29@logic.                  struct semantic email addresses;
stanford.edu. We make no claims as to the optimality of such an         (2) A database (Infomaster) that is queried to determine the
encoding, but present it as an illustration of why such addresses       traditional email addresses of people matching a query;
should be hidden from users.                                            (3) A an email system (Postfix), that is used both to send
emails to (traditional) email addresses and to receive                if one desires. Within small to medium sized communities,
semantically addressed emails; and                                    this sort of behavior is often uncommon since social reper-
(4) Application code (ISEA) to glue the previous three                cussions occur when a community member violates commu-
pieces together.                                                      nity rules. Within larger communities, security policies may
   A typical interaction with the system interacts with the           need to be enacted to limit who is allowed to send to whom.
components in the following order:                                    On the public Internet, however, SEA abuse is much harder
                                                                      to control. Of course, this is true for any publicly available
(1) The user constructs a semantic email address using                email address, whether or not SEA is used, as is true now
our SEA-address creating interface. Optionally, the user              for webmaster@site.com.
can use the interface to query the database to determine the             On the open Internet, the more interesting issue is that
list of recipients who are addressed by the semantic email            of data ownership and authentication. Preventing any user
address he or she has constructed.                                    from changing their profile so that they spoof being part of
                                                                      a restricted group on the open Internet will require new so-
(2) The user sends an email to this address using the                 lutions. One can imagine many SEA systems, only some
email client of his or her choice.                                    of which implement profile authentication. Users requiring
                                                                      security will want to use a SEA system that authenticates
(3) The email is received by the ISEA Postfix applica-                 profile properties against at least local permissions and sim-
tion. This triggers an action that calls the ISEA application         ilarly authenticates incoming messages.
code, which translates the semantic email address into a                 And on the open Internet, SEA with subscription to public
database query and queries the database. The result of this           invisible properties becomes indistinguishable from seman-
database query is a list of (traditional) email addresses.            tic RSS, except for the authentication issue.

(4) ISEA uses Postfix to forward the email to this list                                 Dealing With Errors
of email addresses, placing the addresses in the blind carbon
copy header of the email, and the semantic email address in           Keeping Information Up to Date
the to header of the email. 2                                         One of the most powerful aspects of a semantic email ad-
                                                                      dress is that the set of recipients that it addresses changes
(5) The emails are received by the recipients using the               over time, as the properties of the people in the database
email clients of their choice.                                        change, and as new people and added to the database and
                                                                      old ones removed. Ideally, the database is always kept up to
   In the case of a user replying to an email with a semantic         date, to reflect the changing realities of the world. In prac-
email address, step (1) is skipped and the process starts at          tice, information in the database is not always 100% accu-
step (2).                                                             rate.
                                                                         Inaccurate information can lead to people receiving an
                  Security and Privacy                                email who should not, and people not receiving an email
                                                                      when they should. It is important that there is a way for
Intra-Enterprise                                                      users of the system to ensure that their information is cor-
An interesting possibility is for people outside an enterprise        rect, either by editing it themselves or by having an autho-
to use SEA to send email to members of the enterprise based           rized administrator change the information for them.
on their semantic description, without knowing who they                  In ISEA, users have password-protected access to their
are. For example, I might want to send a message to the               profiles via a Web interface. All information about a person
lead developer of a particular product at Yahoo!, but I do not        is therefore controllable by the individual himself. Users are
know his or her name or email address, and Yahoo! might               expected to keep their own profiles up to date. As one might
not want me to know his or her name or email address. How-            expect in a large organization, not all information is always
ever, they still might want to allow me to contact him or her.        accurate. However, the authors note that in the case of fre-
By exposing a semantic email addressing form to me, they              quently used semantic emailing addresses (for example, ”all
can allow this in a simple way. This leads to considerations          people interested in SEA”), the relevant information is more
of the use of SEA on the open Internet.                               often kept up to date than in the case of information that is
                                                                      has not yet been used for semantic email addressing.
SEA on the Open Internet
SEA is ideal for targeted email addressing, essentially the           Bounced Emails
opposite of spam. However, SEA is also ripe for abuse -               Bounced and delayed emails are handled by forwarding the
it can easily be used to send exceedingly untargeted emails           error messages back to the sender. This works fine, unless
    2                                                                 the semantic email address is meant anonymize the recipi-
      Note that this means that ISEA will receive another copy of
the email, which can lead to an infinite loop if we are not careful.   ent or recipients. In this case, the error message should not
This is avoided by adding an email header called X-ISEA which         be forwarded back to the sender. Instead a message should
we use to flag whether this message has been seen before or not        be sent back that masks the identity of the recipients, e.g.
(i.e. messages with this header have been seen before and should      ”Your email message has not been sent to the intended re-
not be processed).                                                    cipient. We apologize for the inconvenience.” We note that
these problems and solutions are no different than those for      filter those messages using production rules. An interesting
traditional mailing lists.                                        feature of this system was that it allowed users to send to a
                                                                  special mailbox called “Anyone” from which anyone could
                     User Adoption                                subsequently choose to receive messages based on produc-
In our prototype implementation with DERI Galway and              tion rules. This flips on its head the nature of widely broad-
DERI Innsbruck, as well as even DERI Stanford, we cur-            cast emails - instead of starting with receiving all emails and
rently have these three sites as one selection property. The      whittling them down based on filtering rules, the user in-
total number of people varies, but numbers less than 500          stead starts with an empty inbox and pulls in emails of in-
currently. We will soon add DERI Korea. Within each site,         terest based on rules. This is quite similar to the subscrip-
there are research groups. We currently have a total of fif-       tion model of RSS, the syndication format popular today.
teen (14) different groups. Each group has a leader and a         As RSS feeds contain more and more semantic information,
set of members. Each person can currently change anything         the semantic subscription model exemplified by Information
in the set of profiles, much as with a wiki. New groups and        Lens may become more commonplace.
people can be added by anyone. Each person has a profile              More recently, MailSMORE (Kalyanpur et al. ) allows
of personal data including interests. Anyone can add a new        the user to annotate the content of an email with RDF triples,
interest. This openness is by design after consideration by       and automatically also includes RDF triples generated based
a working design council. The openness will eventually be         on the standard headers of an email such as the To, From,
modified in accordance with the security and privacy con-          Subject and Body fields. This can be used for semantic fil-
siderations above.                                                tering and filing of emails.
   Even among technical people, adoption has to be carefully         The M ANGROVE system (Mcdowell et al. 2004a; Mc-
managed. A very common remark is that people trust their          Dowell et al. 2004b; Etzioni et al. 2003) takes this idea fur-
existing email lists and don’t trust SEA virtual lists. When      ther but allowing not just structured email content, but also
asked about the specific form their trust takes, people say        semantic email processes which allow email clients to be
that they know who is on the existing email lists. In at least    scripted with declarative workflow that can be used to auto-
the case of DERI Innsbruck, this turns out to be incorrect:       matically aggregate information obtained from many email
only the administrator can see who is on the list. In contrast,   responses, automatically resend emails to people who have
anyone can check to see to whom a SEA message will be             not responded, or to analyze the semantic content of incom-
sent.                                                             ing email messages and respond accordingly.
   Similarly, people have remarked that they will not be able        Most relevantly, Microsoft Exchange 2003 allows admin-
to use SEA messages in the same way that they use email           istrators to create query-based distribution groups, which are
from existing email lists. Again, when asked for specifics,        essentially mailing lists whose recipients are based on an
they say they store messages from specific email lists in spe-     LDAP query run at the time of the email sending. This alle-
cific folders and then use these emails to send to the email       viates much of the administrative work required to maintain
lists later. Of course, this is exactly the same with SEA vir-    a mailing list. However, because the mailing lists may be
tual email lists, and this methodology is facilitated with the    created by an administrator only, they do not allow the full
ISEA nickname.                                                    power of SEA. In fact, users are completely shielded from
   In general, SEA provides all of the same information and       the fact that a distribution group is query based: each query-
functionality as existing email lists, and more. Whatever         based distribution group is given a name, and thus looks just
worked with static email lists works with SEA virtual email       like a regular mailing list to an outsider.
lists, with less effort. Thus it appears that there are initial
psychological, rather than technical barriers to SEA adop-                              Future Work
tion, and we see this conservatism being quickly disappear-       In addition to the work suggested by the security and pri-
ing.                                                              vacy discussion above, there is a wide range of improve-
                                                                  ments planned for our prototype, ranging from the near-term
                    Standardization                               simple to long-range difficult. We have a parallel effort to
                                                                  develop SEA-specifc email clients to solve the problem of
SEA does not require that all implementations use the same        the ugly semantic email address. But our major develop-
addressing scheme; it can vary from organization to orga-         ment work is in the area of user interface to make SEA look
nization or even from server to server within an organiza-        more like existing popular email interfaces.
tion. However, we would expect one or more standards to              Allowing external groups to use SEA, is much more prob-
emerge over time. This would provide the benefit that email        lematic as it means that the issues of distributed permissions
clients could provide better built-in support for SEA, includ-    and authentication must be addressed. There is also the gen-
ing SEA address editing, analysis, and search.                    eral semantic problem of linking to arbitrary external se-
                                                                  mantic sources on unifying the results. Much of this second
                      Related Work                                problem has been in principle solved with Infomaster(Gene-
Several other authors have seen the value in bringing seman-      sereth et al. 1997). However, there remains the ontological
tics to emails, though all in a somewhat different way. For       engineering problem of constructing proper hierarchies of
example, the Information Lens system (Malone et al. 1987)         ontologies so that Charles can use such them to declare that
allowed users to send semistructured email messages and to        he filters out BMW K-series Motorcycles from all of those
about BMW Motorcycles. (Proper SEA design assumes that            A. Kalyanpur, B. Parsia, J. Hendler, and J. Golbeck.
superclasses of expressed interest are not of interest to the     Smore - semantic markup, ontology, and rdf editor.
person profiled, but subclasses are.)                              http://www.mindswap.org/papers/SMORE.pdf.
   An interesting possibility to help control spam is seman-      T. Malone, K. Grant, F. Turbak, S. Brobst, and M. Cohen.
tic filtering and filing of emails. One could write semantic        Intelligent information-sharing systems. Commun. ACM,
email rules based on not just the standard email fields, but       30(5):390–402, 1987.
also the semantic email address. For example, one might
                                                                  L. Mcdowell, O. Etzioni, and A. Halevy. Semantic email:
classify all email as spam that comes from someone not
                                                                  Theory and applications. Web Semantics: Science, Services
in a whitelist and without a FOAF that references some-
                                                                  and Agents on the World Wide Web, 2(2):153–183, Decem-
one within two degrees of separation and no common in-
                                                                  ber 2004.
terest. This semantic filtering and filing could be extremely
effective, especially if combined with semantic email con-        L. McDowell, O. Etzioni, A. Halevy, and H. Levy. Seman-
tent. How to generate user interfaces that allow these sort       tic email. In WWW ’04: Proceedings of the 13th inter-
of filters to be specified and how to efficiently filter large        national conference on World Wide Web, pages 244–254,
numbers of emails against a semantic email address are in-        New York, NY, USA, 2004. ACM Press.
teresting questions.

                       Conclusion
In this paper, we have introduced the notion of semantic
email addressing, which provides all of the functionality
of static email mailing lists. In addition, we have demon-
strated with our prototype implementation some additional
functionality possible. The first benefit is simply that users
maintain their own profiles, thereby controlling their email
streams. It is no longer necessary to subscribe, unsubscribe,
and change email addresses in static lists. Nor do list admin-
istrators have to establish, maintain, and filter email mailing
lists.
   The targeted nature of a semantically addressed email is
powerful and could be used to combat unintentional spam.
Furthermore, since it can facilitate the contacting of individ-
uals based on their characteristics, it can be used to preserve
the privacy of email addresses and even individual identities.
   SEA is a simple concept, and one which we hope will
soon be incorporated into commercial email systems, but
which we are already deploying in set of academic insti-
tutes distributed over international sites and consisting of
various research groups and people with varying interests.
SEA allows each person to be precisely targeted according
to their site, group, and interests in ways not feasible with
static email mailing lists. Because it not only frees adminis-
trators from maintaining static lists but also allows people to
have more control over their email based upon local control
of their semantic data, SEA could be the “killer app” of the
Semantic Web.

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