Apalancamiento AT/PATRIM * 100%

The Social Network function returns interpersonal chains that most

strongly link the user to a given or . This information can be used

to initiate a chain of recommendation , whereby the user s interest in the target

or is relayed from to along the chain, or as a

kind of letter of recommendation that the user can use to introduce themselves directly to the target, as described by Kautz [Kautz97]. The function identifies chains of maximum length 4 nodes, or 3 degrees of separation. Some limit is necessary to ensure that only socially meaningful chains are returned. Travers and Milgram s [Travers69] results suggest a maximum limit, showing that by exploiting individual knowledge of professional contacts, a chain of 4 or 5 degrees of separation was sufficient to link any two individuals. They do not

degrees of separation was chosen as representing the largest chain that can

comfortably be expressed in plain English ( your friend Tom is currently

working with her boss, Steve ).

Although the usefulness of social networks in innovation is clear, the likelihood that any one user will wish to identify a social network to any one other is obviously small. Given the large number of social connections that will exist within a typical user population, it does not make sense to dynamically maintain social links and chains as we do for other relationships used by the system. Instead, they are identified and evaluated as required, using a low-priority snapshot clone of the fact-base so that the processing involved does not interrupt other users interaction with the system. Nonetheless, the dynamic pair scores that are maintained are available in the snapshot for use by the social link evaluation routines, so the performance benefits of a largely dynamic system are not lost to this function.

Social chains are identified using backward chaining, a process whereby the inference engine actively seeks to satisfy a goal condition indicated by an

Bob Ann Craig Dave Ed Frank Grace Friend (100) 80 ₇₀ 70 90 70 75 80 20

executed stored query in this case, a social link from the user to the target. For chain identification, a link is considered to exist from one individual to another if they have temporally overlapping periods of membership in at least one Group, or the second individual lists the first as a friend. Let us examine the mechanism by which the chain Ann-Frank-Grace-Ed, represented in Figure 5.13, is identified (for clarity, names rather than identifiers are shown). A query is executed to

identify facts Ann Ed i.e. those facts that match

(Connection (from Ann) (to Ed)). Because the fact template is

enabled for backward chaining, the inference engine asserts a fact to represent the

goal condition: (need-Connection (from Ann) (to Ed) (via )). Two rules are

implemented that trigger on need-Connection facts:

If (need-Connection (from Person_V) (to Person_W) (via $Via)) and a direct social link exists between them, and (need-Connection (from Person_U) (to Person_W) (via )), assert (Connection (from U) (to W) (via $Via)). Thus a match for the query is identified.

If (need-Connection (from Person_X) (to Person_Z) (via $Via)) and a direct social link exists from Person X to Person Y, and $Via currently references fewer than 3 intermediate nodes, assert (need-Connection (from Y) (to Z) (via $Via+Person_Y)).

Hence, each final Connection fact, returned by the query, contains the chain of

Persons that comprised the connection in its slot e.g. (Connection (from

Ann) (to Ed) (via Frank Grace)). The process repeats automatically until all chains, of 3 degrees of separation or less, from the user to the specified Person have been identified; the query then returns a vector of these chains. If the target that the user wishes to connect with is a Group rather than an individual Person, chains are sought for each of the Group s current membership in turn.

In accordance with Granovetter s definition of link strength [Granovetter73], the following factors are assessed to evaluate individual

recency, duration and timescale of collaboration number of collaborations

number of instances of joint attendance at physical project meetings number of instances of co-authorship of media items

These are codified as sets of JESS fuzzy sets [Orchard01], representing the strength of social link that a particular value for any of these factors indicates. Each of these sets is administrator-modifiable, allowing the social network engine to be configured for the particular conditions and attitudes of the organisation in which the platform will be deployed. In the default configuration, for example, a period of collaboration of at least 2 years indicates a very strong social link; in an environment characterised by very low employee churn, though, this might be considered only to suggest a moderately strong connection.

Regardless of these factors, a full strength link is considered to exist from

one individual to another if the second has listed the first in their

slot. The link score is recorded, together with the identifiers of

s, s and s that form the most significant

evidence of the link s existence. This allows the nature of the link to be explained to the user. Link evaluations are cached until all identified chains have been scored as different chains will commonly share one or two links (in Figure 5.6, for example, two chains contain the link from Ann to Bob).

To calculate the overall strength of a chain, the system takes into account not only the strengths of link between immediately adjacent links in the chain, but also any parallel links that have been identified between non-adjacent links. Referring again to Figure 5.13, Nardi tells us that even a weak direct link from Ann to Ed could quickly be reinvigorated, but in this case there is no direct link at all. The shortest (geodesic) chain is via Craig, but the link from Ann to Craig is

scored very low; we can imagine, for example, that it stems from historic co- membership of a large virtual community. A more promising network to exploit

might be that through Frank and Grace though it involves an additional degree

of separation, each link is scored highly, indicating active, well-established working relationships between each pair of individuals. However, though Bob and Ann have not collaborated professionally, their friendship yields two additional strong connections to Ed; one through Dave, the other via Craig. This second chain is assumed to offer the strongest overall connection from Ann to Ed, as a recommendation from Bob to Craig would reinforce the weak direct social link that already exists between Craig and Ann.

As Granovetter observed, in determining the most effective social bridge to an individual or community, we must consider not only the strengths of individual social ties at the present moment, but also the number of social ties that must be traversed [Granovetter73]. We would expect a reasonably strong two-step chain to be preferable to a slightly stronger three-step one, so the overall chain scores are scaled according to the number of links that they contain. Additionally, where the user has requested networks to a Group, the chain score is weighted according to the duration and recency of the chain terminator s involvement in that Group. Again, the degree of weighting applied can be modified by the platform s administrator. Finally the chains are sorted according to their score and the five strongest returned.

5.4 Summary

Pair-wise relationships between topics, interests and interest groups form the basis of a dynamic, rule-maintained network of organisational relationships. In conjunction with rich query-driven functionality, also implemented within the reasoning engine, they allow a comprehensive suite of awareness-, community-

these services to satisfy the requirements for innovation support summarised in Chapter 4.