(iv) Diagnostic Module (data driven) - the user feeds the Advisory System data
on the particular circumstances where guidance is required. He/she knows what criteria will define the problem but is unable to use the Information Base directly.
There is no manual analogue. The non-computerised equivalent would be
someone approaching an expert for advice as to how to tackle a problem. Data entry will be through a type of form filling. The user will be shown a number of possible topics where data can be declared by "ticking off' items from a menu. The system will use this data to direct the user to the relevant part of the Information Base. In the Guidelines module, the initial menu of topics might include subject, site and activity. To obtain advice as to how to dispose of sharps after an operation, the user might select "sharps" off a subject menu, "ward" off a site menu, and "disposal" off an activity menu.
(v) Diagnostic Module (data + hypothesis driven) - this is the most
sophisticated form o f access and is intended primarily for the least expert user. The user is unable to address the Information Base directly and does not know the subject area sufficiently to specify defining criteria for the problem. Some data is declared to the Advisory System which triggers off a consultation in which the user is asked questions in order to obtain information which allow the Advisory System to function as if a type (iv) user was using it. Interaction will again be through a kind of form filling. A user of the Guidelines module might declare "sharps" off a subject menu but not "wards" off a site menu or "disposal" off an activity menu. The user does not know which topics are relevant to his problem. The system will use the data declared but will also ask questions in order to decide upon the relevant section of the Information Base. The system will need to prompt the user to provide data on the site and the activity.
I : AN EXPERT ADVISORY SYSTEM FOR AIDS. HIV 69
HIGH
▲
Type V user (data+hypothesis driven) *_______________ *
Degree of Expertise o f System Interface
Type IV user (data driven) *_______________ *
Type III user (menu driven) *____________ * A A Expert System T i 1 Expert Advisory System
Type II user Advisory
(keyword - subject) System
*_____________ * LOW LOW Type I user (keyword - item) * ____________ * i ▼ --- ► HIGH Degree o f Expertise of User
Figure 1.3
1: AN EXPERT ADVISORY SYSTEM FOR AIDS/HIV 70
The different forms of access and their relationships to Expert Advisory Systems and to existing non-computerised systems are shown in Figures 1.3 and 1.4. The two models show how the various forms of access can be used by a range of users. For example, the most sophisticated interface, the data and hypothesis mode, will be used primarily by the least expert user. Flowever, it could also be used by an expert in a critiquing role.
It was decided that the complete concept of the Expert Advisory System would only initially be developed for the clinical module. The clinical module of the information system already catered for type (i), (ii) and (iii) users seeking information about various attributes of AIDS related disorders. This would be extended to cater for type (iv) and (v) users by designing an interface which referenced the same advice but indirectly by the user describing the signs and
symptoms of the patient. This interface would be based on the differential
diagnosis model that was observed in clinical decision making during the development of the expert system.
It was also decided that, for the moment, no diagnostic facility would exist in the general public module. This is because it covers such a vast range of topics that it is extremely difficult to formulate rules that help decide which section of the
Information Base should be addressed. A possible way o f overcoming this
problem is to request the user to initially express which part o f the overall module he is interested in, e.g., AIDS and employment, or Transmission o f AIDS, or AIDS and children at school. "True" diagnostic access could then be made available once in that section.
I : AN EXPERT ADVISORY SYSTEM FOR AIDS/H1V 71 HIGH Degree o f Advice Given
Advice Type V user (needs substantial external assistance)
other *---*
than that in
manual Type IV user (needs some external assistance)
needed *---*
Type III user (uses contents)
all advice *--- *
needed available
from Type II user (uses index)
manual *---*
LOW
LOW
Type I user (direct access) *___________________ * ---►
HIGH Degree of Expertise of User
Figure 1.4
AN EXPERT ADVISORY SYSTEM FOR AIDS/HIV 72
The main expert to be used for the development of the Expert Advisory System would be Dr Charles Farthing, who had made the greatest contribution to both the Expert System and the clinical module of the Information System. He had also been the most enthusiastic and co-operative expert throughout the various
developments. He agreed to help the development team again when he was
approached regarding the Expert Advisory System.
The user groups would consist mainly of the ones that were used for the evaluations o f the Expert System and the Information System, as long as they all agreed.
1.6.3 The Development Period
During the development o f the clinical module o f the AIDS Information System, clinical knowledge on AIDS was structured in terms of a 'disease tree'. This described a disease in terms of its background, presenting signs and symptoms, treatment, prognosis, prophylaxis, and related diseases (see section 1.5.3). This proved to be useful in the construction of the differential diagnosis component of the Expert Advisory System.
The most useful areas were the presenting signs and symptoms of the disease and the relationship of the disease to other diseases. In the Information System, this information was presented as text files which contained a lot of detail for clarity and readability. This knowledge had to be reviewed, re-structured and represented differently for use with a differential diagnosis approach.
Other knowledge required was obtained from published sources or extracted from the mind of the human expert being used, Dr Farthing. As in the development o f
1 AN EXPERT ADVISORY SYSTEM FOR AIDS/HIV 73
the Expert System and the Information System, an iterative process was used to build the latest tool (see figure 1.2). As discussed before (see section 1.5.3.1) this involved building a prototype, followed by a cyclic process of extending, refining and re-refining the system.
The knowledge that had been acquired was represented in a form that would enable the system to match a description of a patient's symptoms to a disease. This required that the system know what observations might be made of the patient and how these related to diseases within its domain.
The development team continued to use PROLOG because of the same reasons as those given for the development o f the Information System (see section 1.5.3). The need to use a flexible and powerful logic based language was even greater for the development of the Expert Advisory System because o f the abstract nature in which decision rules had to be represented.
The inference engine, a mechanism to control the way in which knowledge is
applied, was important. This is because knowledge of diseases and their
associated findings cannot by themselves form a diagnostic interface. The design of the inference engine had to satisfy one constraint, namely to allow the user to feel in control.
When using the system, the user/expert was required to enter observations o f the patient through menus, which appeared as forms. This had the advantage of restricting communication to structures which could be recognised by the system, as opposed to free format entry which can cause problems. One o f these problems could be if the words entered by the expert were miss-spelt, abbreviated or just input in a different format than that recognised by the system. Fortunately, experts
1 AN EXPERT ADVISORY SYSTEM FOR AIDS/HIV 74
or users preferred to make as few keystrokes as possible and were quite happy to have a list of items to choose from.
As each basic symptom exhibited by a patient is declared, the expert is required to enter the attributes of each symptom (see Appendix A). The system will then give a differential o f possible diseases the patient has presented as an ordered menu of items. The expert can then activate these items and access information as in the menu mode described in section 1.5.3.3.
The expert has the facility to ask how a particular diagnosis was reached. He can also add to the list of symptoms, which might result in a different diagnosis. The diagnostic interface does not exclude the other features o f the system like the menu, keyword and free-text searches. These facilities remain active and can be called as necessary.
Appendix A, which contains demonstrations of the AIDS Expert Advisory System in use, shows the layout of the menu items and instructions as they appear on the
computer screen. During the development o f the Expert System and the
Information System it was realised that a lot o f potential users were computer phobic especially those who had never used a computer before. Therefore, the
Expert Advisory System was designed so that it was user-friendly. All the
required instructions were always displayed at the top of each screen. In this way, there was no need for the user to have to remember or learn any commands.
Most of these instructions consisted of function keys. It was discovered that users became more confident when they were told that only a small part of the keyboard, i.e. the function keys, would be needed to use the System. However, to maintain
1 : AN EXPERT ADVISORY SYSTEM FOR AIDS/HIV 75
flexibility, the keys normally associated with moving the curser or highlighter on the screen display were also available.
1.6.4 The Implementation Period
Different parts of the Expert Advisory System were installed for use by a large number of collaborating groups and individuals, many o f whom had been contacted during the development of the Information System. These included the following:
• Healthline
• British Medical Association.
• Israeli National Working Party on AIDS
• World Health Organisation (European Region)
• Health Education Board of the Irish Republic in Dublin
• British Computer Society Health Specialist Care Group
• AIDS National Helpline
• West Midlands Drug Users Working Party
• Health Education Authority, U. K.
• Coventry Community Drug Team
• St. Stephen's Hospital, London
• St. Mary's Hospital, London
• Middlesex Hospital, London
For many o f the users, there appeared to be little difference between the Expert Advisory System and the Information System. Only the physicians who dealt with AIDS patients were given access to the complete Expert Advisory System for evaluation purposes. The feedback facility was also made available as it had